/
cppi_dma.c
1553 lines (1315 loc) · 44 KB
/
cppi_dma.c
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/*
* Copyright (C) 2005-2006 by Texas Instruments
*
* This file implements a DMA interface using TI's CPPI DMA.
* For now it's DaVinci-only, but CPPI isn't specific to DaVinci or USB.
* The TUSB6020, using VLYNQ, has CPPI that looks much like DaVinci.
*/
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include "musb_core.h"
#include "musb_debug.h"
#include "cppi_dma.h"
/* CPPI DMA status 7-mar-2006:
*
* - See musb_{host,gadget}.c for more info
*
* - Correct RX DMA generally forces the engine into irq-per-packet mode,
* which can easily saturate the CPU under non-mass-storage loads.
*
* NOTES 24-aug-2006 (2.6.18-rc4):
*
* - peripheral RXDMA wedged in a test with packets of length 512/512/1.
* evidently after the 1 byte packet was received and acked, the queue
* of BDs got garbaged so it wouldn't empty the fifo. (rxcsr 0x2003,
* and RX DMA0: 4 left, 80000000 8feff880, 8feff860 8feff860; 8f321401
* 004001ff 00000001 .. 8feff860) Host was just getting NAKed on tx
* of its next (512 byte) packet. IRQ issues?
*
* REVISIT: the "transfer DMA" glue between CPPI and USB fifos will
* evidently also directly update the RX and TX CSRs ... so audit all
* host and peripheral side DMA code to avoid CSR access after DMA has
* been started.
*/
/* REVISIT now we can avoid preallocating these descriptors; or
* more simply, switch to a global freelist not per-channel ones.
* Note: at full speed, 64 descriptors == 4K bulk data.
*/
#define NUM_TXCHAN_BD 64
#define NUM_RXCHAN_BD 64
static inline void cpu_drain_writebuffer(void)
{
wmb();
#ifdef CONFIG_CPU_ARM926T
/* REVISIT this "should not be needed",
* but lack of it sure seemed to hurt ...
*/
asm("mcr p15, 0, r0, c7, c10, 4 @ drain write buffer\n");
#endif
}
static inline struct cppi_descriptor *cppi_bd_alloc(struct cppi_channel *c)
{
struct cppi_descriptor *bd = c->freelist;
if (bd)
c->freelist = bd->next;
return bd;
}
static inline void
cppi_bd_free(struct cppi_channel *c, struct cppi_descriptor *bd)
{
if (!bd)
return;
bd->next = c->freelist;
c->freelist = bd;
}
/*
* Start DMA controller
*
* Initialize the DMA controller as necessary.
*/
/* zero out entire rx state RAM entry for the channel */
static void cppi_reset_rx(struct cppi_rx_stateram __iomem *rx)
{
musb_writel(&rx->rx_skipbytes, 0, 0);
musb_writel(&rx->rx_head, 0, 0);
musb_writel(&rx->rx_sop, 0, 0);
musb_writel(&rx->rx_current, 0, 0);
musb_writel(&rx->rx_buf_current, 0, 0);
musb_writel(&rx->rx_len_len, 0, 0);
musb_writel(&rx->rx_cnt_cnt, 0, 0);
}
/* zero out entire tx state RAM entry for the channel */
static void cppi_reset_tx(struct cppi_tx_stateram __iomem *tx, u32 ptr)
{
musb_writel(&tx->tx_head, 0, 0);
musb_writel(&tx->tx_buf, 0, 0);
musb_writel(&tx->tx_current, 0, 0);
musb_writel(&tx->tx_buf_current, 0, 0);
musb_writel(&tx->tx_info, 0, 0);
musb_writel(&tx->tx_rem_len, 0, 0);
/* musb_writel(&tx->tx_dummy, 0, 0); */
musb_writel(&tx->tx_complete, 0, ptr);
}
static void cppi_pool_init(struct cppi *cppi, struct cppi_channel *c)
{
int j;
/* initialize channel fields */
c->head = NULL;
c->tail = NULL;
c->last_processed = NULL;
c->channel.status = MUSB_DMA_STATUS_UNKNOWN;
c->controller = cppi;
c->is_rndis = 0;
c->freelist = NULL;
/* build the BD Free list for the channel */
for (j = 0; j < NUM_TXCHAN_BD + 1; j++) {
struct cppi_descriptor *bd;
dma_addr_t dma;
bd = dma_pool_alloc(cppi->pool, GFP_KERNEL, &dma);
bd->dma = dma;
cppi_bd_free(c, bd);
}
}
static int cppi_channel_abort(struct dma_channel *);
static void cppi_pool_free(struct cppi_channel *c)
{
struct cppi *cppi = c->controller;
struct cppi_descriptor *bd;
(void) cppi_channel_abort(&c->channel);
c->channel.status = MUSB_DMA_STATUS_UNKNOWN;
c->controller = NULL;
/* free all its bds */
bd = c->last_processed;
do {
if (bd)
dma_pool_free(cppi->pool, bd, bd->dma);
bd = cppi_bd_alloc(c);
} while (bd);
c->last_processed = NULL;
}
static int cppi_controller_start(struct dma_controller *c)
{
struct cppi *controller;
void __iomem *tibase;
int i;
controller = container_of(c, struct cppi, controller);
/* do whatever is necessary to start controller */
for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
controller->tx[i].transmit = true;
controller->tx[i].index = i;
}
for (i = 0; i < ARRAY_SIZE(controller->rx); i++) {
controller->rx[i].transmit = false;
controller->rx[i].index = i;
}
/* setup BD list on a per channel basis */
for (i = 0; i < ARRAY_SIZE(controller->tx); i++)
cppi_pool_init(controller, controller->tx + i);
for (i = 0; i < ARRAY_SIZE(controller->rx); i++)
cppi_pool_init(controller, controller->rx + i);
tibase = controller->tibase;
INIT_LIST_HEAD(&controller->tx_complete);
/* initialise tx/rx channel head pointers to zero */
for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
struct cppi_channel *tx_ch = controller->tx + i;
struct cppi_tx_stateram __iomem *tx;
INIT_LIST_HEAD(&tx_ch->tx_complete);
tx = tibase + DAVINCI_TXCPPI_STATERAM_OFFSET(i);
tx_ch->state_ram = tx;
cppi_reset_tx(tx, 0);
}
for (i = 0; i < ARRAY_SIZE(controller->rx); i++) {
struct cppi_channel *rx_ch = controller->rx + i;
struct cppi_rx_stateram __iomem *rx;
INIT_LIST_HEAD(&rx_ch->tx_complete);
rx = tibase + DAVINCI_RXCPPI_STATERAM_OFFSET(i);
rx_ch->state_ram = rx;
cppi_reset_rx(rx);
}
/* enable individual cppi channels */
musb_writel(tibase, DAVINCI_TXCPPI_INTENAB_REG,
DAVINCI_DMA_ALL_CHANNELS_ENABLE);
musb_writel(tibase, DAVINCI_RXCPPI_INTENAB_REG,
DAVINCI_DMA_ALL_CHANNELS_ENABLE);
/* enable tx/rx CPPI control */
musb_writel(tibase, DAVINCI_TXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_ENABLE);
musb_writel(tibase, DAVINCI_RXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_ENABLE);
/* disable RNDIS mode, also host rx RNDIS autorequest */
musb_writel(tibase, DAVINCI_RNDIS_REG, 0);
musb_writel(tibase, DAVINCI_AUTOREQ_REG, 0);
return 0;
}
/*
* Stop DMA controller
*
* De-Init the DMA controller as necessary.
*/
static int cppi_controller_stop(struct dma_controller *c)
{
struct cppi *controller;
void __iomem *tibase;
int i;
struct musb *musb;
controller = container_of(c, struct cppi, controller);
musb = controller->musb;
tibase = controller->tibase;
/* DISABLE INDIVIDUAL CHANNEL Interrupts */
musb_writel(tibase, DAVINCI_TXCPPI_INTCLR_REG,
DAVINCI_DMA_ALL_CHANNELS_ENABLE);
musb_writel(tibase, DAVINCI_RXCPPI_INTCLR_REG,
DAVINCI_DMA_ALL_CHANNELS_ENABLE);
dev_dbg(musb->controller, "Tearing down RX and TX Channels\n");
for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
/* FIXME restructure of txdma to use bds like rxdma */
controller->tx[i].last_processed = NULL;
cppi_pool_free(controller->tx + i);
}
for (i = 0; i < ARRAY_SIZE(controller->rx); i++)
cppi_pool_free(controller->rx + i);
/* in Tx Case proper teardown is supported. We resort to disabling
* Tx/Rx CPPI after cleanup of Tx channels. Before TX teardown is
* complete TX CPPI cannot be disabled.
*/
/*disable tx/rx cppi */
musb_writel(tibase, DAVINCI_TXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_DISABLE);
musb_writel(tibase, DAVINCI_RXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_DISABLE);
return 0;
}
/* While dma channel is allocated, we only want the core irqs active
* for fault reports, otherwise we'd get irqs that we don't care about.
* Except for TX irqs, where dma done != fifo empty and reusable ...
*
* NOTE: docs don't say either way, but irq masking **enables** irqs.
*
* REVISIT same issue applies to pure PIO usage too, and non-cppi dma...
*/
static inline void core_rxirq_disable(void __iomem *tibase, unsigned epnum)
{
musb_writel(tibase, DAVINCI_USB_INT_MASK_CLR_REG, 1 << (epnum + 8));
}
static inline void core_rxirq_enable(void __iomem *tibase, unsigned epnum)
{
musb_writel(tibase, DAVINCI_USB_INT_MASK_SET_REG, 1 << (epnum + 8));
}
/*
* Allocate a CPPI Channel for DMA. With CPPI, channels are bound to
* each transfer direction of a non-control endpoint, so allocating
* (and deallocating) is mostly a way to notice bad housekeeping on
* the software side. We assume the irqs are always active.
*/
static struct dma_channel *
cppi_channel_allocate(struct dma_controller *c,
struct musb_hw_ep *ep, u8 transmit)
{
struct cppi *controller;
u8 index;
struct cppi_channel *cppi_ch;
void __iomem *tibase;
struct musb *musb;
controller = container_of(c, struct cppi, controller);
tibase = controller->tibase;
musb = controller->musb;
/* ep0 doesn't use DMA; remember cppi indices are 0..N-1 */
index = ep->epnum - 1;
/* return the corresponding CPPI Channel Handle, and
* probably disable the non-CPPI irq until we need it.
*/
if (transmit) {
if (index >= ARRAY_SIZE(controller->tx)) {
dev_dbg(musb->controller, "no %cX%d CPPI channel\n", 'T', index);
return NULL;
}
cppi_ch = controller->tx + index;
} else {
if (index >= ARRAY_SIZE(controller->rx)) {
dev_dbg(musb->controller, "no %cX%d CPPI channel\n", 'R', index);
return NULL;
}
cppi_ch = controller->rx + index;
core_rxirq_disable(tibase, ep->epnum);
}
/* REVISIT make this an error later once the same driver code works
* with the other DMA engine too
*/
if (cppi_ch->hw_ep)
dev_dbg(musb->controller, "re-allocating DMA%d %cX channel %p\n",
index, transmit ? 'T' : 'R', cppi_ch);
cppi_ch->hw_ep = ep;
cppi_ch->channel.status = MUSB_DMA_STATUS_FREE;
cppi_ch->channel.max_len = 0x7fffffff;
dev_dbg(musb->controller, "Allocate CPPI%d %cX\n", index, transmit ? 'T' : 'R');
return &cppi_ch->channel;
}
/* Release a CPPI Channel. */
static void cppi_channel_release(struct dma_channel *channel)
{
struct cppi_channel *c;
void __iomem *tibase;
/* REVISIT: for paranoia, check state and abort if needed... */
c = container_of(channel, struct cppi_channel, channel);
tibase = c->controller->tibase;
if (!c->hw_ep)
dev_dbg(c->controller->musb->controller,
"releasing idle DMA channel %p\n", c);
else if (!c->transmit)
core_rxirq_enable(tibase, c->index + 1);
/* for now, leave its cppi IRQ enabled (we won't trigger it) */
c->hw_ep = NULL;
channel->status = MUSB_DMA_STATUS_UNKNOWN;
}
/* Context: controller irqlocked */
static void
cppi_dump_rx(int level, struct cppi_channel *c, const char *tag)
{
void __iomem *base = c->controller->mregs;
struct cppi_rx_stateram __iomem *rx = c->state_ram;
musb_ep_select(base, c->index + 1);
dev_dbg(c->controller->musb->controller,
"RX DMA%d%s: %d left, csr %04x, "
"%08x H%08x S%08x C%08x, "
"B%08x L%08x %08x .. %08x"
"\n",
c->index, tag,
musb_readl(c->controller->tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + 4 * c->index),
musb_readw(c->hw_ep->regs, MUSB_RXCSR),
musb_readl(&rx->rx_skipbytes, 0),
musb_readl(&rx->rx_head, 0),
musb_readl(&rx->rx_sop, 0),
musb_readl(&rx->rx_current, 0),
musb_readl(&rx->rx_buf_current, 0),
musb_readl(&rx->rx_len_len, 0),
musb_readl(&rx->rx_cnt_cnt, 0),
musb_readl(&rx->rx_complete, 0)
);
}
/* Context: controller irqlocked */
static void
cppi_dump_tx(int level, struct cppi_channel *c, const char *tag)
{
void __iomem *base = c->controller->mregs;
struct cppi_tx_stateram __iomem *tx = c->state_ram;
musb_ep_select(base, c->index + 1);
dev_dbg(c->controller->musb->controller,
"TX DMA%d%s: csr %04x, "
"H%08x S%08x C%08x %08x, "
"F%08x L%08x .. %08x"
"\n",
c->index, tag,
musb_readw(c->hw_ep->regs, MUSB_TXCSR),
musb_readl(&tx->tx_head, 0),
musb_readl(&tx->tx_buf, 0),
musb_readl(&tx->tx_current, 0),
musb_readl(&tx->tx_buf_current, 0),
musb_readl(&tx->tx_info, 0),
musb_readl(&tx->tx_rem_len, 0),
/* dummy/unused word 6 */
musb_readl(&tx->tx_complete, 0)
);
}
/* Context: controller irqlocked */
static inline void
cppi_rndis_update(struct cppi_channel *c, int is_rx,
void __iomem *tibase, int is_rndis)
{
/* we may need to change the rndis flag for this cppi channel */
if (c->is_rndis != is_rndis) {
u32 value = musb_readl(tibase, DAVINCI_RNDIS_REG);
u32 temp = 1 << (c->index);
if (is_rx)
temp <<= 16;
if (is_rndis)
value |= temp;
else
value &= ~temp;
musb_writel(tibase, DAVINCI_RNDIS_REG, value);
c->is_rndis = is_rndis;
}
}
static void cppi_dump_rxbd(const char *tag, struct cppi_descriptor *bd)
{
pr_debug("RXBD/%s %08x: "
"nxt %08x buf %08x off.blen %08x opt.plen %08x\n",
tag, bd->dma,
bd->hw_next, bd->hw_bufp, bd->hw_off_len,
bd->hw_options);
}
static void cppi_dump_rxq(int level, const char *tag, struct cppi_channel *rx)
{
struct cppi_descriptor *bd;
cppi_dump_rx(level, rx, tag);
if (rx->last_processed)
cppi_dump_rxbd("last", rx->last_processed);
for (bd = rx->head; bd; bd = bd->next)
cppi_dump_rxbd("active", bd);
}
/* NOTE: DaVinci autoreq is ignored except for host side "RNDIS" mode RX;
* so we won't ever use it (see "CPPI RX Woes" below).
*/
static inline int cppi_autoreq_update(struct cppi_channel *rx,
void __iomem *tibase, int onepacket, unsigned n_bds)
{
u32 val;
#ifdef RNDIS_RX_IS_USABLE
u32 tmp;
/* assert(is_host_active(musb)) */
/* start from "AutoReq never" */
tmp = musb_readl(tibase, DAVINCI_AUTOREQ_REG);
val = tmp & ~((0x3) << (rx->index * 2));
/* HCD arranged reqpkt for packet #1. we arrange int
* for all but the last one, maybe in two segments.
*/
if (!onepacket) {
#if 0
/* use two segments, autoreq "all" then the last "never" */
val |= ((0x3) << (rx->index * 2));
n_bds--;
#else
/* one segment, autoreq "all-but-last" */
val |= ((0x1) << (rx->index * 2));
#endif
}
if (val != tmp) {
int n = 100;
/* make sure that autoreq is updated before continuing */
musb_writel(tibase, DAVINCI_AUTOREQ_REG, val);
do {
tmp = musb_readl(tibase, DAVINCI_AUTOREQ_REG);
if (tmp == val)
break;
cpu_relax();
} while (n-- > 0);
}
#endif
/* REQPKT is turned off after each segment */
if (n_bds && rx->channel.actual_len) {
void __iomem *regs = rx->hw_ep->regs;
val = musb_readw(regs, MUSB_RXCSR);
if (!(val & MUSB_RXCSR_H_REQPKT)) {
val |= MUSB_RXCSR_H_REQPKT | MUSB_RXCSR_H_WZC_BITS;
musb_writew(regs, MUSB_RXCSR, val);
/* flush writebuffer */
val = musb_readw(regs, MUSB_RXCSR);
}
}
return n_bds;
}
/* Buffer enqueuing Logic:
*
* - RX builds new queues each time, to help handle routine "early
* termination" cases (faults, including errors and short reads)
* more correctly.
*
* - for now, TX reuses the same queue of BDs every time
*
* REVISIT long term, we want a normal dynamic model.
* ... the goal will be to append to the
* existing queue, processing completed "dma buffers" (segments) on the fly.
*
* Otherwise we force an IRQ latency between requests, which slows us a lot
* (especially in "transparent" dma). Unfortunately that model seems to be
* inherent in the DMA model from the Mentor code, except in the rare case
* of transfers big enough (~128+ KB) that we could append "middle" segments
* in the TX paths. (RX can't do this, see below.)
*
* That's true even in the CPPI- friendly iso case, where most urbs have
* several small segments provided in a group and where the "packet at a time"
* "transparent" DMA model is always correct, even on the RX side.
*/
/*
* CPPI TX:
* ========
* TX is a lot more reasonable than RX; it doesn't need to run in
* irq-per-packet mode very often. RNDIS mode seems to behave too
* (except how it handles the exactly-N-packets case). Building a
* txdma queue with multiple requests (urb or usb_request) looks
* like it would work ... but fault handling would need much testing.
*
* The main issue with TX mode RNDIS relates to transfer lengths that
* are an exact multiple of the packet length. It appears that there's
* a hiccup in that case (maybe the DMA completes before the ZLP gets
* written?) boiling down to not being able to rely on CPPI writing any
* terminating zero length packet before the next transfer is written.
* So that's punted to PIO; better yet, gadget drivers can avoid it.
*
* Plus, there's allegedly an undocumented constraint that rndis transfer
* length be a multiple of 64 bytes ... but the chip doesn't act that
* way, and we really don't _want_ that behavior anyway.
*
* On TX, "transparent" mode works ... although experiments have shown
* problems trying to use the SOP/EOP bits in different USB packets.
*
* REVISIT try to handle terminating zero length packets using CPPI
* instead of doing it by PIO after an IRQ. (Meanwhile, make Ethernet
* links avoid that issue by forcing them to avoid zlps.)
*/
static void
cppi_next_tx_segment(struct musb *musb, struct cppi_channel *tx)
{
unsigned maxpacket = tx->maxpacket;
dma_addr_t addr = tx->buf_dma + tx->offset;
size_t length = tx->buf_len - tx->offset;
struct cppi_descriptor *bd;
unsigned n_bds;
unsigned i;
struct cppi_tx_stateram __iomem *tx_ram = tx->state_ram;
int rndis;
/* TX can use the CPPI "rndis" mode, where we can probably fit this
* transfer in one BD and one IRQ. The only time we would NOT want
* to use it is when hardware constraints prevent it, or if we'd
* trigger the "send a ZLP?" confusion.
*/
rndis = (maxpacket & 0x3f) == 0
&& length > maxpacket
&& length < 0xffff
&& (length % maxpacket) != 0;
if (rndis) {
maxpacket = length;
n_bds = 1;
} else {
n_bds = length / maxpacket;
if (!length || (length % maxpacket))
n_bds++;
n_bds = min(n_bds, (unsigned) NUM_TXCHAN_BD);
length = min(n_bds * maxpacket, length);
}
dev_dbg(musb->controller, "TX DMA%d, pktSz %d %s bds %d dma 0x%llx len %u\n",
tx->index,
maxpacket,
rndis ? "rndis" : "transparent",
n_bds,
(unsigned long long)addr, length);
cppi_rndis_update(tx, 0, musb->ctrl_base, rndis);
/* assuming here that channel_program is called during
* transfer initiation ... current code maintains state
* for one outstanding request only (no queues, not even
* the implicit ones of an iso urb).
*/
bd = tx->freelist;
tx->head = bd;
tx->last_processed = NULL;
/* FIXME use BD pool like RX side does, and just queue
* the minimum number for this request.
*/
/* Prepare queue of BDs first, then hand it to hardware.
* All BDs except maybe the last should be of full packet
* size; for RNDIS there _is_ only that last packet.
*/
for (i = 0; i < n_bds; ) {
if (++i < n_bds && bd->next)
bd->hw_next = bd->next->dma;
else
bd->hw_next = 0;
bd->hw_bufp = tx->buf_dma + tx->offset;
/* FIXME set EOP only on the last packet,
* SOP only on the first ... avoid IRQs
*/
if ((tx->offset + maxpacket) <= tx->buf_len) {
tx->offset += maxpacket;
bd->hw_off_len = maxpacket;
bd->hw_options = CPPI_SOP_SET | CPPI_EOP_SET
| CPPI_OWN_SET | maxpacket;
} else {
/* only this one may be a partial USB Packet */
u32 partial_len;
partial_len = tx->buf_len - tx->offset;
tx->offset = tx->buf_len;
bd->hw_off_len = partial_len;
bd->hw_options = CPPI_SOP_SET | CPPI_EOP_SET
| CPPI_OWN_SET | partial_len;
if (partial_len == 0)
bd->hw_options |= CPPI_ZERO_SET;
}
dev_dbg(musb->controller, "TXBD %p: nxt %08x buf %08x len %04x opt %08x\n",
bd, bd->hw_next, bd->hw_bufp,
bd->hw_off_len, bd->hw_options);
/* update the last BD enqueued to the list */
tx->tail = bd;
bd = bd->next;
}
/* BDs live in DMA-coherent memory, but writes might be pending */
cpu_drain_writebuffer();
/* Write to the HeadPtr in state RAM to trigger */
musb_writel(&tx_ram->tx_head, 0, (u32)tx->freelist->dma);
cppi_dump_tx(5, tx, "/S");
}
/*
* CPPI RX Woes:
* =============
* Consider a 1KB bulk RX buffer in two scenarios: (a) it's fed two 300 byte
* packets back-to-back, and (b) it's fed two 512 byte packets back-to-back.
* (Full speed transfers have similar scenarios.)
*
* The correct behavior for Linux is that (a) fills the buffer with 300 bytes,
* and the next packet goes into a buffer that's queued later; while (b) fills
* the buffer with 1024 bytes. How to do that with CPPI?
*
* - RX queues in "rndis" mode -- one single BD -- handle (a) correctly, but
* (b) loses **BADLY** because nothing (!) happens when that second packet
* fills the buffer, much less when a third one arrives. (Which makes this
* not a "true" RNDIS mode. In the RNDIS protocol short-packet termination
* is optional, and it's fine if peripherals -- not hosts! -- pad messages
* out to end-of-buffer. Standard PCI host controller DMA descriptors
* implement that mode by default ... which is no accident.)
*
* - RX queues in "transparent" mode -- two BDs with 512 bytes each -- have
* converse problems: (b) is handled right, but (a) loses badly. CPPI RX
* ignores SOP/EOP markings and processes both of those BDs; so both packets
* are loaded into the buffer (with a 212 byte gap between them), and the next
* buffer queued will NOT get its 300 bytes of data. (It seems like SOP/EOP
* are intended as outputs for RX queues, not inputs...)
*
* - A variant of "transparent" mode -- one BD at a time -- is the only way to
* reliably make both cases work, with software handling both cases correctly
* and at the significant penalty of needing an IRQ per packet. (The lack of
* I/O overlap can be slightly ameliorated by enabling double buffering.)
*
* So how to get rid of IRQ-per-packet? The transparent multi-BD case could
* be used in special cases like mass storage, which sets URB_SHORT_NOT_OK
* (or maybe its peripheral side counterpart) to flag (a) scenarios as errors
* with guaranteed driver level fault recovery and scrubbing out what's left
* of that garbaged datastream.
*
* But there seems to be no way to identify the cases where CPPI RNDIS mode
* is appropriate -- which do NOT include RNDIS host drivers, but do include
* the CDC Ethernet driver! -- and the documentation is incomplete/wrong.
* So we can't _ever_ use RX RNDIS mode ... except by using a heuristic
* that applies best on the peripheral side (and which could fail rudely).
*
* Leaving only "transparent" mode; we avoid multi-bd modes in almost all
* cases other than mass storage class. Otherwise we're correct but slow,
* since CPPI penalizes our need for a "true RNDIS" default mode.
*/
/* Heuristic, intended to kick in for ethernet/rndis peripheral ONLY
*
* IFF
* (a) peripheral mode ... since rndis peripherals could pad their
* writes to hosts, causing i/o failure; or we'd have to cope with
* a largely unknowable variety of host side protocol variants
* (b) and short reads are NOT errors ... since full reads would
* cause those same i/o failures
* (c) and read length is
* - less than 64KB (max per cppi descriptor)
* - not a multiple of 4096 (g_zero default, full reads typical)
* - N (>1) packets long, ditto (full reads not EXPECTED)
* THEN
* try rx rndis mode
*
* Cost of heuristic failing: RXDMA wedges at the end of transfers that
* fill out the whole buffer. Buggy host side usb network drivers could
* trigger that, but "in the field" such bugs seem to be all but unknown.
*
* So this module parameter lets the heuristic be disabled. When using
* gadgetfs, the heuristic will probably need to be disabled.
*/
static bool cppi_rx_rndis = 1;
module_param(cppi_rx_rndis, bool, 0);
MODULE_PARM_DESC(cppi_rx_rndis, "enable/disable RX RNDIS heuristic");
/**
* cppi_next_rx_segment - dma read for the next chunk of a buffer
* @musb: the controller
* @rx: dma channel
* @onepacket: true unless caller treats short reads as errors, and
* performs fault recovery above usbcore.
* Context: controller irqlocked
*
* See above notes about why we can't use multi-BD RX queues except in
* rare cases (mass storage class), and can never use the hardware "rndis"
* mode (since it's not a "true" RNDIS mode) with complete safety..
*
* It's ESSENTIAL that callers specify "onepacket" mode unless they kick in
* code to recover from corrupted datastreams after each short transfer.
*/
static void
cppi_next_rx_segment(struct musb *musb, struct cppi_channel *rx, int onepacket)
{
unsigned maxpacket = rx->maxpacket;
dma_addr_t addr = rx->buf_dma + rx->offset;
size_t length = rx->buf_len - rx->offset;
struct cppi_descriptor *bd, *tail;
unsigned n_bds;
unsigned i;
void __iomem *tibase = musb->ctrl_base;
int is_rndis = 0;
struct cppi_rx_stateram __iomem *rx_ram = rx->state_ram;
struct cppi_descriptor *d;
if (onepacket) {
/* almost every USB driver, host or peripheral side */
n_bds = 1;
/* maybe apply the heuristic above */
if (cppi_rx_rndis
&& is_peripheral_active(musb)
&& length > maxpacket
&& (length & ~0xffff) == 0
&& (length & 0x0fff) != 0
&& (length & (maxpacket - 1)) == 0) {
maxpacket = length;
is_rndis = 1;
}
} else {
/* virtually nothing except mass storage class */
if (length > 0xffff) {
n_bds = 0xffff / maxpacket;
length = n_bds * maxpacket;
} else {
n_bds = length / maxpacket;
if (length % maxpacket)
n_bds++;
}
if (n_bds == 1)
onepacket = 1;
else
n_bds = min(n_bds, (unsigned) NUM_RXCHAN_BD);
}
/* In host mode, autorequest logic can generate some IN tokens; it's
* tricky since we can't leave REQPKT set in RXCSR after the transfer
* finishes. So: multipacket transfers involve two or more segments.
* And always at least two IRQs ... RNDIS mode is not an option.
*/
if (is_host_active(musb))
n_bds = cppi_autoreq_update(rx, tibase, onepacket, n_bds);
cppi_rndis_update(rx, 1, musb->ctrl_base, is_rndis);
length = min(n_bds * maxpacket, length);
dev_dbg(musb->controller, "RX DMA%d seg, maxp %d %s bds %d (cnt %d) "
"dma 0x%llx len %u %u/%u\n",
rx->index, maxpacket,
onepacket
? (is_rndis ? "rndis" : "onepacket")
: "multipacket",
n_bds,
musb_readl(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
& 0xffff,
(unsigned long long)addr, length,
rx->channel.actual_len, rx->buf_len);
/* only queue one segment at a time, since the hardware prevents
* correct queue shutdown after unexpected short packets
*/
bd = cppi_bd_alloc(rx);
rx->head = bd;
/* Build BDs for all packets in this segment */
for (i = 0, tail = NULL; bd && i < n_bds; i++, tail = bd) {
u32 bd_len;
if (i) {
bd = cppi_bd_alloc(rx);
if (!bd)
break;
tail->next = bd;
tail->hw_next = bd->dma;
}
bd->hw_next = 0;
/* all but the last packet will be maxpacket size */
if (maxpacket < length)
bd_len = maxpacket;
else
bd_len = length;
bd->hw_bufp = addr;
addr += bd_len;
rx->offset += bd_len;
bd->hw_off_len = (0 /*offset*/ << 16) + bd_len;
bd->buflen = bd_len;
bd->hw_options = CPPI_OWN_SET | (i == 0 ? length : 0);
length -= bd_len;
}
/* we always expect at least one reusable BD! */
if (!tail) {
WARNING("rx dma%d -- no BDs? need %d\n", rx->index, n_bds);
return;
} else if (i < n_bds)
WARNING("rx dma%d -- only %d of %d BDs\n", rx->index, i, n_bds);
tail->next = NULL;
tail->hw_next = 0;
bd = rx->head;
rx->tail = tail;
/* short reads and other faults should terminate this entire
* dma segment. we want one "dma packet" per dma segment, not
* one per USB packet, terminating the whole queue at once...
* NOTE that current hardware seems to ignore SOP and EOP.
*/
bd->hw_options |= CPPI_SOP_SET;
tail->hw_options |= CPPI_EOP_SET;
for (d = rx->head; d; d = d->next)
cppi_dump_rxbd("S", d);
/* in case the preceding transfer left some state... */
tail = rx->last_processed;
if (tail) {
tail->next = bd;
tail->hw_next = bd->dma;
}
core_rxirq_enable(tibase, rx->index + 1);
/* BDs live in DMA-coherent memory, but writes might be pending */
cpu_drain_writebuffer();
/* REVISIT specs say to write this AFTER the BUFCNT register
* below ... but that loses badly.
*/
musb_writel(&rx_ram->rx_head, 0, bd->dma);
/* bufferCount must be at least 3, and zeroes on completion
* unless it underflows below zero, or stops at two, or keeps
* growing ... grr.
*/
i = musb_readl(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
& 0xffff;
if (!i)
musb_writel(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
n_bds + 2);
else if (n_bds > (i - 3))
musb_writel(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
n_bds - (i - 3));
i = musb_readl(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
& 0xffff;
if (i < (2 + n_bds)) {
dev_dbg(musb->controller, "bufcnt%d underrun - %d (for %d)\n",
rx->index, i, n_bds);
musb_writel(tibase,
DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
n_bds + 2);
}
cppi_dump_rx(4, rx, "/S");
}
/**
* cppi_channel_program - program channel for data transfer
* @ch: the channel
* @maxpacket: max packet size
* @mode: For RX, 1 unless the usb protocol driver promised to treat
* all short reads as errors and kick in high level fault recovery.
* For TX, ignored because of RNDIS mode races/glitches.
* @dma_addr: dma address of buffer
* @len: length of buffer
* Context: controller irqlocked
*/
static int cppi_channel_program(struct dma_channel *ch,
u16 maxpacket, u8 mode,
dma_addr_t dma_addr, u32 len)
{
struct cppi_channel *cppi_ch;
struct cppi *controller;
struct musb *musb;
cppi_ch = container_of(ch, struct cppi_channel, channel);
controller = cppi_ch->controller;
musb = controller->musb;
switch (ch->status) {
case MUSB_DMA_STATUS_BUS_ABORT:
case MUSB_DMA_STATUS_CORE_ABORT:
/* fault irq handler should have handled cleanup */
WARNING("%cX DMA%d not cleaned up after abort!\n",
cppi_ch->transmit ? 'T' : 'R',
cppi_ch->index);
/* WARN_ON(1); */
break;
case MUSB_DMA_STATUS_BUSY:
WARNING("program active channel? %cX DMA%d\n",
cppi_ch->transmit ? 'T' : 'R',
cppi_ch->index);
/* WARN_ON(1); */
break;
case MUSB_DMA_STATUS_UNKNOWN:
dev_dbg(musb->controller, "%cX DMA%d not allocated!\n",
cppi_ch->transmit ? 'T' : 'R',
cppi_ch->index);
/* FALLTHROUGH */
case MUSB_DMA_STATUS_FREE:
break;
}
ch->status = MUSB_DMA_STATUS_BUSY;
/* set transfer parameters, then queue up its first segment */
cppi_ch->buf_dma = dma_addr;
cppi_ch->offset = 0;
cppi_ch->maxpacket = maxpacket;
cppi_ch->buf_len = len;
cppi_ch->channel.actual_len = 0;