diff mbox

[v3,1/2] tpm: reduce poll sleep time in tpm_transmit()

Message ID 20180507160733.8817-2-nayna@linux.vnet.ibm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Nayna May 7, 2018, 4:07 p.m. UTC
tpm_try_transmit currently checks TPM status every 5 msecs between
send and recv. It does so in a loop for the maximum timeout as defined
in the TPM Interface Specification. However, the TPM may return before
5 msecs. Thus the polling interval for each iteration can be reduced,
which improves overall performance. This patch changes the polling sleep
time from 5 msecs to 1 msec.

Additionally, this patch renames TPM_POLL_SLEEP to TPM_TIMEOUT_POLL and
moves it to tpm.h as an enum value.

After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~14 sec to ~10.7 sec.

[1] All tests are performed on an x86 based, locked down, single purpose
closed system. It has Infineon TPM 1.2 using LPC Bus.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
---
 drivers/char/tpm/tpm-interface.c |  2 +-
 drivers/char/tpm/tpm.h           |  3 ++-
 drivers/char/tpm/tpm_tis_core.c  | 10 ++--------
 3 files changed, 5 insertions(+), 10 deletions(-)

Comments

Jay Freyensee May 8, 2018, 4:34 p.m. UTC | #1
>   		do {
> -			tpm_msleep(TPM_POLL_SLEEP);
> +			tpm_msleep(TPM_TIMEOUT_POLL);
>
I'm just curious why it was decided to still use tpm_msleep() here 
instead of usleep_range() which was used in the 2nd patch.

Otherwise,

Acked-by: Jay Freyensee <why2jjj.linux@gmail.com>

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Nayna May 10, 2018, 12:41 p.m. UTC | #2
On 05/08/2018 10:04 PM, J Freyensee wrote:
>
>>           do {
>> -            tpm_msleep(TPM_POLL_SLEEP);
>> +            tpm_msleep(TPM_TIMEOUT_POLL);
>>
> I'm just curious why it was decided to still use tpm_msleep() here 
> instead of usleep_range() which was used in the 2nd patch.

TPM_TIMEOUT_POLL is in msec i.e. 1 msec and usleep_range() is used only 
when timeout is needed in usecs.

>
> Otherwise,
>
> Acked-by: Jay Freyensee <why2jjj.linux@gmail.com>

Thanks !!

Thanks & Regards,
     - Nayna


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Nayna May 14, 2018, 10:39 a.m. UTC | #3
On 05/10/2018 06:11 PM, Nayna Jain wrote:
>
>
> On 05/08/2018 10:04 PM, J Freyensee wrote:
>>
>>>           do {
>>> -            tpm_msleep(TPM_POLL_SLEEP);
>>> +            tpm_msleep(TPM_TIMEOUT_POLL);
>>>
>> I'm just curious why it was decided to still use tpm_msleep() here 
>> instead of usleep_range() which was used in the 2nd patch.
>
> TPM_TIMEOUT_POLL is in msec i.e. 1 msec and usleep_range() is used 
> only when timeout is needed in usecs.

Just to add bit more details:

usleep_range() is used in wait_for_tpm_stat() and get_burstcount() which 
are expected to return quickly. tpm_transmit() is a generic function 
used across all drivers and commands.
Some of the commands (eg. hash, key generation) take longer compared to 
other commands (eg. extend). The sleep time in tpm_transmit is reduced 
but kept in msecs to balance between the smaller and longer commands.

Thanks & Regards,
     - Nayna

>
>>
>> Otherwise,
>>
>> Acked-by: Jay Freyensee <why2jjj.linux@gmail.com>
>
> Thanks !!
>
> Thanks & Regards,
>     - Nayna
>
>

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Jarkko Sakkinen May 14, 2018, 10:46 a.m. UTC | #4
On Mon, May 07, 2018 at 12:07:32PM -0400, Nayna Jain wrote:
> tpm_try_transmit currently checks TPM status every 5 msecs between
> send and recv. It does so in a loop for the maximum timeout as defined
> in the TPM Interface Specification. However, the TPM may return before
> 5 msecs. Thus the polling interval for each iteration can be reduced,
> which improves overall performance. This patch changes the polling sleep
> time from 5 msecs to 1 msec.
> 
> Additionally, this patch renames TPM_POLL_SLEEP to TPM_TIMEOUT_POLL and
> moves it to tpm.h as an enum value.
> 
> After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
> burstcount for 1000 extends improved from ~14 sec to ~10.7 sec.
> 
> [1] All tests are performed on an x86 based, locked down, single purpose
> closed system. It has Infineon TPM 1.2 using LPC Bus.
> 
> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
 
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko
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Jarkko Sakkinen May 14, 2018, 10:47 a.m. UTC | #5
On Mon, May 14, 2018 at 01:46:00PM +0300, Jarkko Sakkinen wrote:
> On Mon, May 07, 2018 at 12:07:32PM -0400, Nayna Jain wrote:
> > tpm_try_transmit currently checks TPM status every 5 msecs between
> > send and recv. It does so in a loop for the maximum timeout as defined
> > in the TPM Interface Specification. However, the TPM may return before
> > 5 msecs. Thus the polling interval for each iteration can be reduced,
> > which improves overall performance. This patch changes the polling sleep
> > time from 5 msecs to 1 msec.
> > 
> > Additionally, this patch renames TPM_POLL_SLEEP to TPM_TIMEOUT_POLL and
> > moves it to tpm.h as an enum value.
> > 
> > After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
> > burstcount for 1000 extends improved from ~14 sec to ~10.7 sec.
> > 
> > [1] All tests are performed on an x86 based, locked down, single purpose
> > closed system. It has Infineon TPM 1.2 using LPC Bus.
> > 
> > Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
>  
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko
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diff mbox

Patch

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 6201aab374e6..e32f6e85dc6d 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -489,7 +489,7 @@  static ssize_t tpm_try_transmit(struct tpm_chip *chip,
 			goto out;
 		}
 
-		tpm_msleep(TPM_TIMEOUT);
+		tpm_msleep(TPM_TIMEOUT_POLL);
 		rmb();
 	} while (time_before(jiffies, stop));
 
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index eedcd9cf30bc..ca05828b6981 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -53,7 +53,8 @@  enum tpm_const {
 enum tpm_timeout {
 	TPM_TIMEOUT = 5,	/* msecs */
 	TPM_TIMEOUT_RETRY = 100, /* msecs */
-	TPM_TIMEOUT_RANGE_US = 300	/* usecs */
+	TPM_TIMEOUT_RANGE_US = 300,	/* usecs */
+	TPM_TIMEOUT_POLL = 1	/* msecs */
 };
 
 /* TPM addresses */
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 5a1f47b43947..493401f5fd39 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -31,12 +31,6 @@ 
 #include "tpm.h"
 #include "tpm_tis_core.h"
 
-/* This is a polling delay to check for status and burstcount.
- * As per ddwg input, expectation is that status check and burstcount
- * check should return within few usecs.
- */
-#define TPM_POLL_SLEEP	1  /* msec */
-
 static void tpm_tis_clkrun_enable(struct tpm_chip *chip, bool value);
 
 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
@@ -90,7 +84,7 @@  static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
 		}
 	} else {
 		do {
-			tpm_msleep(TPM_POLL_SLEEP);
+			tpm_msleep(TPM_TIMEOUT_POLL);
 			status = chip->ops->status(chip);
 			if ((status & mask) == mask)
 				return 0;
@@ -234,7 +228,7 @@  static int get_burstcount(struct tpm_chip *chip)
 		burstcnt = (value >> 8) & 0xFFFF;
 		if (burstcnt)
 			return burstcnt;
-		tpm_msleep(TPM_POLL_SLEEP);
+		tpm_msleep(TPM_TIMEOUT_POLL);
 	} while (time_before(jiffies, stop));
 	return -EBUSY;
 }