Patch "tpm: msleep() delays - replace with usleep_range() in i2c nuvoton driver" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

tpm: msleep() delays - replace with usleep_range() in i2c nuvoton driver

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tpm-msleep-delays-replace-with-usleep_range-in-i2c-nuvoton-driver.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nayna Jain <[email protected]>
Date: Fri, 10 Mar 2017 13:45:53 -0500
Subject: tpm: msleep() delays - replace with usleep_range() in i2c nuvoton driver

From: Nayna Jain <[email protected]>

commit a233a0289cf9a96ef9b42c730a7621ccbf9a6f98 upstream.

Commit 500462a9de65 "timers: Switch to a non-cascading wheel" replaced the 'classic' timer wheel, which aimed for near 'exact' expiry of the timers. Their analysis was that the vast majority of timeout timers are used as safeguards, not as real timers, and are cancelled or rearmed before expiration. The only exception noted to this were networking timers with a small expiry time.

Not included in the analysis was the TPM polling timer, which resulted in a longer normal delay and, every so often, a very long delay. The non-cascading wheel delay is based on CONFIG_HZ. For a description of the different rings and their delays, refer to the comments in kernel/time/timer.c.

Below are the delays given for rings 0 - 2, which explains the longer "normal" delays and the very, long delays as seen on systems with CONFIG_HZ 250.

* HZ 1000 steps
* Level Offset Granularity Range

 *  0      0         1 ms                0 ms - 63 ms
 *  1     64         8 ms               64 ms - 511 ms
 *  2    128        64 ms              512 ms - 4095 ms (512ms - ~4s)

* HZ 250
* Level Offset Granularity Range

 *  0      0         4 ms                0 ms - 255 ms
 *  1     64        32 ms              256 ms - 2047 ms (256ms - ~2s)
 *  2    128       256 ms             2048 ms - 16383 ms (~2s - ~16s)

Below is a comparison of extending the TPM with 1000 measurements, using msleep() vs. usleep_delay() when configured for 1000 hz vs. 250 hz, before and after commit 500462a9de65.

linux-4.7 | msleep() usleep_range()
1000 hz: 0m44.628s | 1m34.497s 29.243s
250 hz: 1m28.510s | 4m49.269s 32.386s

linux-4.7 | min-max (msleep) min-max (usleep_range)
1000 hz: 0:017 - 2:760s | 0:015 - 3:967s 0:014 - 0:418s
250 hz: 0:028 - 1:954s | 0:040 - 4:096s 0:016 - 0:816s

This patch replaces the msleep() with usleep_range() calls in the i2c nuvoton driver with a consistent max range value.

---
 drivers/char/tpm/tpm_i2c_nuvoton.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

@@ -49,9 +49,10 @@
  */
 #define TPM_I2C_MAX_BUF_SIZE           32
 #define TPM_I2C_RETRY_COUNT            32
-#define TPM_I2C_BUS_DELAY              1       /* msec */
-#define TPM_I2C_RETRY_DELAY_SHORT      2       /* msec */
-#define TPM_I2C_RETRY_DELAY_LONG       10      /* msec */
+#define TPM_I2C_BUS_DELAY              1000      	/* usec */
+#define TPM_I2C_RETRY_DELAY_SHORT      (2 * 1000)	/* usec */
+#define TPM_I2C_RETRY_DELAY_LONG       (10 * 1000) 	/* usec */
+#define TPM_I2C_DELAY_RANGE            300		/* usec */
 
 #define OF_IS_TPM2 ((void *)1)
 #define I2C_IS_TPM2 1

@@ -123,7 +124,8 @@ static s32 i2c_nuvoton_write_status(stru
 	/* this causes the current command to be aborted */
 	for (i = 0, status = -1; i < TPM_I2C_RETRY_COUNT && status < 0; i++) {
 		status = i2c_nuvoton_write_buf(client, TPM_STS, 1, &data);
-		msleep(TPM_I2C_BUS_DELAY);
+		usleep_range(TPM_I2C_BUS_DELAY, TPM_I2C_BUS_DELAY
+			     + TPM_I2C_DELAY_RANGE);
 	}
 	return status;
 }

@@ -160,7 +162,8 @@ static int i2c_nuvoton_get_burstcount(st
 			burst_count = min_t(u8, TPM_I2C_MAX_BUF_SIZE, data);
 			break;
 		}
-		msleep(TPM_I2C_BUS_DELAY);
+		usleep_range(TPM_I2C_BUS_DELAY, TPM_I2C_BUS_DELAY
+			     + TPM_I2C_DELAY_RANGE);
 	} while (time_before(jiffies, stop));
 
 	return burst_count;

@@ -203,13 +206,17 @@ static int i2c_nuvoton_wait_for_stat(str
 			return 0;
 
 		/* use polling to wait for the event */
-		ten_msec = jiffies + msecs_to_jiffies(TPM_I2C_RETRY_DELAY_LONG);
+		ten_msec = jiffies + usecs_to_jiffies(TPM_I2C_RETRY_DELAY_LONG);
 		stop = jiffies + timeout;
 		do {
 			if (time_before(jiffies, ten_msec))
-				msleep(TPM_I2C_RETRY_DELAY_SHORT);
+				usleep_range(TPM_I2C_RETRY_DELAY_SHORT,
+					     TPM_I2C_RETRY_DELAY_SHORT
+					     + TPM_I2C_DELAY_RANGE);
 			else
-				msleep(TPM_I2C_RETRY_DELAY_LONG);
+				usleep_range(TPM_I2C_RETRY_DELAY_LONG,
+					     TPM_I2C_RETRY_DELAY_LONG
+					     + TPM_I2C_DELAY_RANGE);
 			status_valid = i2c_nuvoton_check_status(chip, mask,
 								value);
 			if (status_valid)

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/tpm-msleep-delays-replace-with-usleep_range-in-i2c-nuvoton-driver.patch queue-4.11/tpm-add-sleep-only-for-retry-in-i2c_nuvoton_write_status.patch