i2c: Add configurable I2C transfer timeout

This patch introduces CONFIG_I2C_TRANSFER_TIMEOUT_US,
which controls how long to wait for an I2C devices to
produce/accept all the data bytes in a single transfer.
(The device can delay transfer by stretching the clock of
the ack bit.)

The default value of this new setting is 500ms.  Existing
code had timeouts anywhere from tens of milliseconds to a
full second beween various drivers.  Drivers can still have
their own shorter timeouts for setup/communication with the
I2C host controller (as opposed to transactions with I2C
devices on the bus.)

In general, the timeout is not meant to be reached except in
situations where there is already serious problem with the
boot, and serves to make sure that some useful diagnostic
output is produced on the console.

Change-Id: I6423122f32aad1dbcee0bfe240cdaa8cb512791f
Signed-off-by: Jes B. Klinke <jbk@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62278
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 16 insertions, 11 deletions

diff --git a/src/soc/cavium/cn81xx/twsi.c b/src/soc/cavium/cn81xx/twsi.c
index bb91b88ebb..b1c1e66fae 100644
--- a/src/soc/cavium/cn81xx/twsi.c
+++ b/src/soc/cavium/cn81xx/twsi.c
@@ -12,6 +12,7 @@
 #include <delay.h>
 #include <device/mmio.h>
 #include <soc/addressmap.h>
+#include <timer.h>
 
 #define TWSI_THP		24
 
@@ -348,17 +349,15 @@ static u8 twsi_read_status(void *baseaddr)
  *
  * @return	0 for success, 1 if timeout
  */
-static int twsi_wait(void *baseaddr)
+static int twsi_wait(void *baseaddr, struct stopwatch *timeout)
 {
-	unsigned long timeout = 500000;
 	u8 twsi_ctl;
 
 	printk(BIOS_SPEW, "%s(%p)\n", __func__, baseaddr);
 	do {
 		twsi_ctl = twsi_read_ctl(baseaddr);
 		twsi_ctl &= TWSI_CTL_IFLG;
-		timeout--;
-	} while (!twsi_ctl && timeout > 0);
+	} while (!twsi_ctl && !stopwatch_expired(timeout));
 
 	printk(BIOS_SPEW, "  return: %u\n", !twsi_ctl);
 	return !twsi_ctl;
@@ -438,10 +437,12 @@ static int twsi_start(void *baseaddr)
 {
 	int result;
 	u8 stat;
+	struct stopwatch timeout;
 
 	printk(BIOS_SPEW, "%s(%p)\n", __func__, baseaddr);
+	stopwatch_init_usecs_expire(&timeout, CONFIG_I2C_TRANSFER_TIMEOUT_US);
 	twsi_write_ctl(baseaddr, TWSI_CTL_STA | TWSI_CTL_ENAB);
-	result = twsi_wait(baseaddr);
+	result = twsi_wait(baseaddr, &timeout);
 	if (result) {
 		stat = twsi_read_status(baseaddr);
 		printk(BIOS_SPEW, "%s: result: 0x%x, status: 0x%x\n", __func__,
@@ -475,9 +476,11 @@ static int twsi_write_data(void *baseaddr, const u8 slave_addr,
 	union twsx_sw_twsi twsi_sw;
 	unsigned int curr = 0;
 	int result;
+	struct stopwatch timeout;
 
 	printk(BIOS_SPEW, "%s(%p, 0x%x, %p, 0x%x)\n", __func__, baseaddr,
 	       slave_addr, buffer, length);
+	stopwatch_init_usecs_expire(&timeout, CONFIG_I2C_TRANSFER_TIMEOUT_US);
 	result = twsi_start(baseaddr);
 	if (result) {
 		printk(BIOS_ERR, "%s: Could not start BUS transaction\n",
@@ -485,7 +488,7 @@ static int twsi_write_data(void *baseaddr, const u8 slave_addr,
 		return -1;
 	}
 
-	result = twsi_wait(baseaddr);
+	result = twsi_wait(baseaddr, &timeout);
 	if (result) {
 		printk(BIOS_ERR, "%s: wait failed\n", __func__);
 		return result;
@@ -500,7 +503,7 @@ static int twsi_write_data(void *baseaddr, const u8 slave_addr,
 	twsi_write_ctl(baseaddr, TWSI_CTL_ENAB);
 
 	printk(BIOS_SPEW, "%s: Waiting\n", __func__);
-	result = twsi_wait(baseaddr);
+	result = twsi_wait(baseaddr, &timeout);
 	if (result) {
 		printk(BIOS_ERR, "%s: Timed out writing slave address 0x%x\n",
 		      __func__, slave_addr);
@@ -521,7 +524,7 @@ static int twsi_write_data(void *baseaddr, const u8 slave_addr,
 		twsi_write_sw(baseaddr, twsi_sw);
 		twsi_write_ctl(baseaddr, TWSI_CTL_ENAB);
 
-		result = twsi_wait(baseaddr);
+		result = twsi_wait(baseaddr, &timeout);
 		if (result) {
 			printk(BIOS_ERR, "%s: Timed out writing data to 0x%x\n",
 			      __func__, slave_addr);
@@ -549,16 +552,18 @@ static int twsi_read_data(void *baseaddr, const u8 slave_addr,
 	union twsx_sw_twsi twsi_sw;
 	unsigned int curr = 0;
 	int result;
+	struct stopwatch timeout;
 
 	printk(BIOS_SPEW, "%s(%p, 0x%x, %p, %u)\n", __func__, baseaddr,
 	       slave_addr, buffer, length);
+	stopwatch_init_usecs_expire(&timeout, CONFIG_I2C_TRANSFER_TIMEOUT_US);
 	result = twsi_start(baseaddr);
 	if (result) {
 		printk(BIOS_ERR, "%s: start failed\n", __func__);
 		return result;
 	}
 
-	result = twsi_wait(baseaddr);
+	result = twsi_wait(baseaddr, &timeout);
 	if (result) {
 		printk(BIOS_ERR, "%s: wait failed\n", __func__);
 		return result;
@@ -574,7 +579,7 @@ static int twsi_read_data(void *baseaddr, const u8 slave_addr,
 	twsi_write_sw(baseaddr, twsi_sw);
 	twsi_write_ctl(baseaddr, TWSI_CTL_ENAB);
 
-	result = twsi_wait(baseaddr);
+	result = twsi_wait(baseaddr, &timeout);
 	if (result) {
 		printk(BIOS_ERR, "%s: waiting for sending addr failed\n", __func__);
 		return result;
@@ -590,7 +595,7 @@ static int twsi_read_data(void *baseaddr, const u8 slave_addr,
 		twsi_write_ctl(baseaddr, TWSI_CTL_ENAB |
 				((curr < length - 1) ? TWSI_CTL_AAK : 0));
 
-		result = twsi_wait(baseaddr);
+		result = twsi_wait(baseaddr, &timeout);
 		if (result) {
 			printk(BIOS_ERR, "%s: waiting for data failed\n",
 			       __func__);