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p8-i2c: Remove force reset
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Force reset was added as an attempt to work around some issues with TPM
devices locking up their I2C bus. In that particular case the problem
was that the device would hold the SCL line down permanently due to a
device firmware bug. The force reset doesn't actually do anything to
alleviate the situation here, it just happens to reset the internal
master state enough to make the I2C driver appear to work until
something tries to access the bus again.

On P9 systems with secure boot enabled there is the added problem
of the "diagostic mode" not being supported on I2C masters A,B,C and
D. Diagnostic mode allows the SCL and SDA lines to be driven directly
by software. Without this force reset is impossible to implement.

This patch removes the force reset functionality entirely since:

	a) it doesn't do what it's supposed to, and
	b) it's butt ugly code

Additionally, turn p8_i2c_reset_engine() into p8_i2c_reset_port().
There's no need to reset every port on a master in response to an
error that occurred on a specific port.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
(cherry picked from commit 49656a1)
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
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@oohal @stewartsmith
oohal authored and stewartsmith committed May 23, 2018
1 parent 652c0dd commit d523a21
Showing 1 changed file with 38 additions and 135 deletions.
173 changes: 38 additions & 135 deletions hw/p8-i2c.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -516,151 +516,54 @@ 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)
static int p8_i2c_reset_port(struct p8_i2c_master_port *p)
{
struct p8_i2c_master_port *p;
uint64_t mode;
int rc;
struct p8_i2c_master *master = p->master;
int reset_loops, rc;
uint64_t status;

/* 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);
/* FIXME: this should per per-port rather than per-master */
master->state = state_error;

/*
* Put the master into enhanced STOP mode when recovering the
* port. This causes the master to send additional STOP conditions
* to work around some particularly stupid I2C devices and it's
* required on secure I2C masters since they will not send a bare
* stop condition.
*/
rc = p8_i2c_prog_mode(p, true);
if (rc) {
log_simple_error(&e_info(OPAL_RC_I2C_RESET), "I2C: Failed "
"to reset port busy on i2c engine\n");
return;
log_simple_error(&e_info(OPAL_RC_I2C_RESET),
"I2C: Failed to enable enhanced mode\n");
return -1;
}
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");
rc = xscom_write(master->chip_id, master->xscom_base +
I2C_CMD_REG, I2C_CMD_WITH_STOP);
if (rc)
goto err;

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");
/* Wait for COMMAND COMPLETE */
for (reset_loops = 0; reset_loops < 10; reset_loops++) {
time_wait_ms(10);

time_wait_us_nopoll(10);
rc = xscom_write(master->chip_id,
master->xscom_base + I2C_SET_S_SDA_REG,
0);
rc = xscom_read(master->chip_id,
master->xscom_base + I2C_STAT_REG,
&status);
if (rc)
prlog(PR_ERR, "I2C: sendStop: fail set 2 S_SDA\n");
goto err;

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");
if (status & I2C_STAT_CMD_COMP)
break;
}
}

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;
if (status & I2C_STAT_CMD_COMP)
return 0;
err:
prerror("I2C: Failed to reset c%de%dp%d\n",
master->chip_id, master->engine_id, p->port_num);
return -1;
}

static void p8_i2c_status_error(struct p8_i2c_master_port *port,
Expand Down Expand Up @@ -699,7 +602,7 @@ static void p8_i2c_status_error(struct p8_i2c_master_port *port,
*/
p8_i2c_complete_request(master, req, req->result);
} else {
if (p8_i2c_reset_engine(master))
if (p8_i2c_reset_port(port))
goto exit;
/* Enable the interrupt */
p8_i2c_enable_irqs(master);
Expand Down

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