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p8-i2c reset things manually in some error conditions
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It appears that our reset code wasn't entirely correct, and what we're
meant to do is reset each port and wait for command complete. In the
event where that fails, we can then bitbang things to recover to a state
where at least the i2c engine isn't in a weird state.

Practically, this means that "i2cdetect -y 10; i2cdetect -y 10" (where 10
is the bus where a TPM is attached, typically p8e1p2) doesn't hard lock
the machine (things are still bad and you won't reboot successfully, but
it's *better*).

one downside to this patch is that we spend a *long* time in OPAL (tens
of ms) when doing the reset. This is something that we really need to fix,
as it's not at all nice. The full fix for this though will involve changing
a decent chunk of the p8-i2c code, as we don't want to write *any* registers
while doing this extended reset (while existing code checks status a bit
later).

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
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@stewartsmith
stewartsmith committed Dec 2, 2016
1 parent 61784ac commit cf6ec98
Showing 1 changed file with 157 additions and 22 deletions.
179 changes: 157 additions & 22 deletions hw/p8-i2c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -171,7 +171,11 @@ DEFINE_LOG_ENTRY(OPAL_RC_I2C_RESET, OPAL_INPUT_OUTPUT_ERR_EVT, OPAL_I2C,
#define I2C_RESIDUAL_BACK_END PPC_BITMASK(16, 31)

/* Port busy register */
#define I2C_PORT_BUYS_REG 0xe
#define I2C_PORT_BUSY_REG 0xe
#define I2C_SET_S_SCL_REG 0xd
#define I2C_RESET_S_SCL_REG 0xf
#define I2C_SET_S_SDA_REG 0x10
#define I2C_RESET_S_SDA_REG 0x11

enum p8_i2c_master_type {
I2C_POWER8,
Expand Down Expand Up @@ -207,13 +211,15 @@ struct p8_i2c_master {
struct timer sensor_cache;
uint8_t recovery_pass;
struct list_node link;
struct list_head ports;
};

struct p8_i2c_master_port {
struct i2c_bus bus; /* Abstract bus struct for the client */
struct p8_i2c_master *master;
uint32_t port_num;
uint32_t bit_rate_div; /* Divisor to set bus speed*/
struct list_node link;
};

struct p8_i2c_request {
Expand Down Expand Up @@ -463,6 +469,153 @@ static void p8_i2c_translate_error(struct i2c_request *req, uint64_t status)
req->result = OPAL_I2C_TIMEOUT;
}

static void p8_i2c_force_reset(struct p8_i2c_master *master)
{
struct p8_i2c_master_port *p;
uint64_t mode;
int rc;

/* Reset the i2c engine */
rc = xscom_write(master->chip_id, master->xscom_base +
I2C_RESET_I2C_REG, 0);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET), "I2C: Failed "
"to reset the i2c engine\n");
return;
}
time_wait_us_nopoll(10);
/* Reset port busy */
rc = xscom_write(master->chip_id, master->xscom_base +
I2C_PORT_BUSY_REG, 0x8000000000000000ULL);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET), "I2C: Failed "
"to reset port busy on i2c engine\n");
return;
}
time_wait_us_nopoll(10);
list_for_each(&master->ports, p, link) {
mode = 0;
mode = SETFIELD(I2C_MODE_PORT_NUM, mode, p->port_num);
mode = SETFIELD(I2C_MODE_BIT_RATE_DIV, mode, p->bit_rate_div);
mode |= I2C_MODE_DIAGNOSTIC;
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_MODE_REG,
mode);
if (rc)
prlog(PR_ERR, "I2C: Failed to write the MODE_REG\n");

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_RESET_S_SCL_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: Failed to reset S_SCL\n");

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_SET_S_SCL_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: Failed to set S_SCL\n");

/* Manually reset */
time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_RESET_S_SCL_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: sendStop: fail reset S_SCL\n");

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_RESET_S_SDA_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: sendStop: fail reset S_SDA\n");

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_SET_S_SCL_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: sendStop: fail set S_SCL\n");

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_SET_S_SDA_REG,
0);
if (rc)
prlog(PR_ERR, "I2C: sendStop: fail set 2 S_SDA\n");

mode ^= I2C_MODE_DIAGNOSTIC;
time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_MODE_REG,
mode);
if (rc)
prlog(PR_ERR, "I2C: Failed to write the MODE_REG\n");
}
}

static int p8_i2c_reset_engine(struct p8_i2c_master *master)
{
struct p8_i2c_master_port *p;
int reset_loops;
int rc;
uint64_t status;

list_for_each(&master->ports, p, link) {
/*
* Reset each port by issuing a STOP command to slave.
*
* Reprogram the mode register with 'enhanced bit' set
*/
rc = p8_i2c_prog_mode(p, true);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET),
"I2C: Failed to program the MODE_REG\n");
return -1;
}

/* Send an immediate stop */
master->state = state_error;
rc = xscom_write(master->chip_id, master->xscom_base +
I2C_CMD_REG, I2C_CMD_WITH_STOP);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET),
"I2C: Failed to issue immediate STOP\n");
return -1;
}

/* Wait for COMMAND COMPLETE */
reset_loops = 0;
do {
rc = xscom_read(master->chip_id,
master->xscom_base + I2C_STAT_REG,
&status);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_TRANSFER),
"I2C: Failed to read the STAT_REG\n");
return -1;
}
if (! (status & I2C_STAT_CMD_COMP)) {
time_wait_ms(10);
if (reset_loops++ == 5) {
prlog(PR_WARNING, "I2C: Retrying reset, with force!\n");
p8_i2c_force_reset(master);
continue;
}
if (reset_loops == 10) {
log_simple_error(&e_info(OPAL_RC_I2C_TRANSFER),
"I2C: Failed to recover i2c engine\n");
break;
}
}
} while (! (status & I2C_STAT_CMD_COMP));
}
return 0;
}

static void p8_i2c_status_error(struct p8_i2c_master_port *port,
struct i2c_request *req,
uint64_t status)
Expand Down Expand Up @@ -495,30 +648,10 @@ static void p8_i2c_status_error(struct p8_i2c_master_port *port,
*/
p8_i2c_complete_request(master, req, req->result);
} else {
/*
* Reset the bus by issuing a STOP command to slave.
*
* Reprogram the mode register with 'enhanced bit' set
*/
rc = p8_i2c_prog_mode(port, true);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET), "I2C: "
"Failed to program the MODE_REG\n");
if (p8_i2c_reset_engine(master))
goto exit;
}

/* Enable the interrupt */
p8_i2c_enable_irqs(master);

/* Send an immediate stop */
master->state = state_error;
rc = xscom_write(master->chip_id, master->xscom_base +
I2C_CMD_REG, I2C_CMD_WITH_STOP);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET), "I2C: "
"Failed to issue immediate STOP\n");
goto exit;
}
}
return;

Expand Down Expand Up @@ -1363,6 +1496,7 @@ static void p8_i2c_init_one(struct dt_node *i2cm, enum p8_i2c_master_type type)

master->fifo_size = GETFIELD(I2C_EXTD_STAT_FIFO_SIZE, ex_stat);
list_head_init(&master->req_list);
list_head_init(&master->ports);

/* Check if interrupt is usable */
master->irq_ok = p8_i2c_has_irqs(master);
Expand Down Expand Up @@ -1422,6 +1556,7 @@ static void p8_i2c_init_one(struct dt_node *i2cm, enum p8_i2c_master_type type)
port->bus.set_req_timeout = p8_i2c_set_request_timeout;
port->bus.run_req = p8_i2c_run_request;
i2c_add_bus(&port->bus);
list_add_tail(&master->ports, &port->link);

/* Add OPAL properties to the bus node */
p8_i2c_add_bus_prop(port);
Expand Down

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