[PATCH 1/1] i2c: nvidia-gpu: Handle timeout correctly in gpu_i2c_check_status()

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/1850238

Nvidia card may come with a "phantom" UCSI device, and its driver gets
stuck in probe routine, prevents any system PM operations like suspend.

There's an unaccounted case that the target time can equal to jiffies in
gpu_i2c_check_status(), let's solve that by using readl_poll_timeout()
instead of jiffies comparison functions.

Fixes: c71bcdcb42a7 ("i2c: add i2c bus driver for NVIDIA GPU")
Suggested-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Reviewed-by: Ajay Gupta <ajayg at nvidia.com>
Tested-by: Ajay Gupta <ajayg at nvidia.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
(cherry picked from commit d944b27df121e2ee854a6c2fad13d6c6300792d4 linux-next)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/i2c/busses/i2c-nvidia-gpu.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/i2c/busses/i2c-nvidia-gpu.c b/drivers/i2c/busses/i2c-nvidia-gpu.c
index 5a1235fd86bb..32cd62188a3d 100644
--- a/drivers/i2c/busses/i2c-nvidia-gpu.c
+++ b/drivers/i2c/busses/i2c-nvidia-gpu.c
@@ -8,6 +8,7 @@
 #include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
@@ -75,20 +76,15 @@ static void gpu_enable_i2c_bus(struct gpu_i2c_dev *i2cd)
 
 static int gpu_i2c_check_status(struct gpu_i2c_dev *i2cd)
 {
-	unsigned long target = jiffies + msecs_to_jiffies(1000);
 	u32 val;
+	int ret;
 
-	do {
-		val = readl(i2cd->regs + I2C_MST_CNTL);
-		if (!(val & I2C_MST_CNTL_CYCLE_TRIGGER))
-			break;
-		if ((val & I2C_MST_CNTL_STATUS) !=
-				I2C_MST_CNTL_STATUS_BUS_BUSY)
-			break;
-		usleep_range(500, 600);
-	} while (time_is_after_jiffies(target));
-
-	if (time_is_before_jiffies(target)) {
+	ret = readl_poll_timeout(i2cd->regs + I2C_MST_CNTL, val,
+				 !(val & I2C_MST_CNTL_CYCLE_TRIGGER) ||
+				 (val & I2C_MST_CNTL_STATUS) != I2C_MST_CNTL_STATUS_BUS_BUSY,
+				 500, 1000 * USEC_PER_MSEC);
+
+	if (ret) {
 		dev_err(i2cd->dev, "i2c timeout error %x\n", val);
 		return -ETIMEDOUT;
 	}
-- 
2.17.1