Re: [PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Jarkko Sakkinen]

On Tue, Apr 17, 2018 at 09:12:46AM -0400, Nayna Jain wrote:
> The TPM burstcount and status commands are supposed to return very
> quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
> in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
> directly.
> 
> After this change, performance on a TPM 1.2 with an 8 byte burstcount for
> 1000 extends improved from ~10.7 sec to ~7 sec.
> 
> [1] From TCG Specification "TCG PC Client Specific TPM Interface
> Specification (TIS), Family 1.2":
> 
> "NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
> take 84 us, which is a long time to stall the CPU. Chipsets may not be
> designed to post this much data to LPC; therefore, the CPU itself is
> stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
> even if the TPM_STS_x.burstCount field is a high value, software SHOULD
> be interruptible during this period."
> 
> [2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
> (PTP) Specification":
> 
> "It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
> 84 us. Chipsets may not be designed to post this much data to LPC;
> therefore, the CPU itself is stalled for much of this time. Sending 1 kB
> would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
> high value, software should be interruptible during this period. For SPI,
> assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
> to move 256B of data. Sending 1kB would take about 500 usec. If the
> transactions are done using 4 bytes at a time, then it would take about
> 1 msec. to transfer 1kB of data."
> 
> Signed-off-by: Nayna Jain 

Great, thanks for finding those references. Kind of stuff that I will
forget within months and have to revisit with git blame/log :-)

Reviewed-by: Jarkko Sakkinen 

/Jarkko

Re: [PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Jarkko Sakkinen]

On Tue, Apr 17, 2018 at 09:12:46AM -0400, Nayna Jain wrote:
> The TPM burstcount and status commands are supposed to return very
> quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
> in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
> directly.
> 
> After this change, performance on a TPM 1.2 with an 8 byte burstcount for
> 1000 extends improved from ~10.7 sec to ~7 sec.
> 
> [1] From TCG Specification "TCG PC Client Specific TPM Interface
> Specification (TIS), Family 1.2":
> 
> "NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
> take 84 us, which is a long time to stall the CPU. Chipsets may not be
> designed to post this much data to LPC; therefore, the CPU itself is
> stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
> even if the TPM_STS_x.burstCount field is a high value, software SHOULD
> be interruptible during this period."
> 
> [2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
> (PTP) Specification":
> 
> "It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
> 84 us. Chipsets may not be designed to post this much data to LPC;
> therefore, the CPU itself is stalled for much of this time. Sending 1 kB
> would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
> high value, software should be interruptible during this period. For SPI,
> assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
> to move 256B of data. Sending 1kB would take about 500 usec. If the
> transactions are done using 4 bytes at a time, then it would take about
> 1 msec. to transfer 1kB of data."
> 
> Signed-off-by: Nayna Jain 

Great, thanks for finding those references. Kind of stuff that I will
forget within months and have to revisit with git blame/log :-)

Reviewed-by: Jarkko Sakkinen 

/Jarkko

Re: [PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Mimi Zohar]

On Tue, 2018-04-17 at 09:12 -0400, Nayna Jain wrote:
> The TPM burstcount and status commands are supposed to return very
> quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
> in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
> directly.
> 
> After this change, performance on a TPM 1.2 with an 8 byte burstcount for
> 1000 extends improved from ~10.7 sec to ~7 sec.
> 
> [1] From TCG Specification "TCG PC Client Specific TPM Interface
> Specification (TIS), Family 1.2":
> 
> "NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
> take 84 us, which is a long time to stall the CPU. Chipsets may not be
> designed to post this much data to LPC; therefore, the CPU itself is
> stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
> even if the TPM_STS_x.burstCount field is a high value, software SHOULD
> be interruptible during this period."
> 
> [2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
> (PTP) Specification":
> 
> "It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
> 84 us. Chipsets may not be designed to post this much data to LPC;
> therefore, the CPU itself is stalled for much of this time. Sending 1 kB
> would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
> high value, software should be interruptible during this period. For SPI,
> assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
> to move 256B of data. Sending 1kB would take about 500 usec. If the
> transactions are done using 4 bytes at a time, then it would take about
> 1 msec. to transfer 1kB of data."
> 
> Signed-off-by: Nayna Jain 

Reviewed-by: Mimi Zohar 


> ---
>  drivers/char/tpm/tpm.h  | 4 +++-
>  drivers/char/tpm/tpm_tis_core.c | 5 +++--
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 7e797377e1eb..f0e4d290c347 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -54,7 +54,9 @@ enum tpm_timeout {
>   TPM_TIMEOUT = 5,/* msecs */
>   TPM_TIMEOUT_RETRY = 100, /* msecs */
>   TPM_TIMEOUT_RANGE_US = 300, /* usecs */
> - TPM_TIMEOUT_POLL = 1/* msecs */
> + TPM_TIMEOUT_POLL = 1,   /* msecs */
> + TPM_TIMEOUT_USECS_MIN = 100,  /* usecs */
> + TPM_TIMEOUT_USECS_MAX = 500  /* usecs */
>  };
> 
>  /* TPM addresses */
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 021e6b68f2db..5bba5c662423 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -84,7 +84,8 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>   }
>   } else {
>   do {
> - tpm_msleep(TPM_TIMEOUT_POLL);
> + usleep_range(TPM_TIMEOUT_USECS_MIN,
> + TPM_TIMEOUT_USECS_MAX);
>   status = chip->ops->status(chip);
>   if ((status & mask) == mask)
>   return 0;
> @@ -226,7 +227,7 @@ static int get_burstcount(struct tpm_chip *chip)
>   burstcnt = (value >> 8) & 0x;
>   if (burstcnt)
>   return burstcnt;
> - tpm_msleep(TPM_TIMEOUT_POLL);
> + usleep_range(TPM_TIMEOUT_USECS_MIN, TPM_TIMEOUT_USECS_MAX);
>   } while (time_before(jiffies, stop));
>   return -EBUSY;
>  }

Re: [PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Mimi Zohar]

On Tue, 2018-04-17 at 09:12 -0400, Nayna Jain wrote:
> The TPM burstcount and status commands are supposed to return very
> quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
> in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
> directly.
> 
> After this change, performance on a TPM 1.2 with an 8 byte burstcount for
> 1000 extends improved from ~10.7 sec to ~7 sec.
> 
> [1] From TCG Specification "TCG PC Client Specific TPM Interface
> Specification (TIS), Family 1.2":
> 
> "NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
> take 84 us, which is a long time to stall the CPU. Chipsets may not be
> designed to post this much data to LPC; therefore, the CPU itself is
> stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
> even if the TPM_STS_x.burstCount field is a high value, software SHOULD
> be interruptible during this period."
> 
> [2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
> (PTP) Specification":
> 
> "It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
> 84 us. Chipsets may not be designed to post this much data to LPC;
> therefore, the CPU itself is stalled for much of this time. Sending 1 kB
> would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
> high value, software should be interruptible during this period. For SPI,
> assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
> to move 256B of data. Sending 1kB would take about 500 usec. If the
> transactions are done using 4 bytes at a time, then it would take about
> 1 msec. to transfer 1kB of data."
> 
> Signed-off-by: Nayna Jain 

Reviewed-by: Mimi Zohar 


> ---
>  drivers/char/tpm/tpm.h  | 4 +++-
>  drivers/char/tpm/tpm_tis_core.c | 5 +++--
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 7e797377e1eb..f0e4d290c347 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -54,7 +54,9 @@ enum tpm_timeout {
>   TPM_TIMEOUT = 5,/* msecs */
>   TPM_TIMEOUT_RETRY = 100, /* msecs */
>   TPM_TIMEOUT_RANGE_US = 300, /* usecs */
> - TPM_TIMEOUT_POLL = 1/* msecs */
> + TPM_TIMEOUT_POLL = 1,   /* msecs */
> + TPM_TIMEOUT_USECS_MIN = 100,  /* usecs */
> + TPM_TIMEOUT_USECS_MAX = 500  /* usecs */
>  };
> 
>  /* TPM addresses */
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 021e6b68f2db..5bba5c662423 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -84,7 +84,8 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>   }
>   } else {
>   do {
> - tpm_msleep(TPM_TIMEOUT_POLL);
> + usleep_range(TPM_TIMEOUT_USECS_MIN,
> + TPM_TIMEOUT_USECS_MAX);
>   status = chip->ops->status(chip);
>   if ((status & mask) == mask)
>   return 0;
> @@ -226,7 +227,7 @@ static int get_burstcount(struct tpm_chip *chip)
>   burstcnt = (value >> 8) & 0x;
>   if (burstcnt)
>   return burstcnt;
> - tpm_msleep(TPM_TIMEOUT_POLL);
> + usleep_range(TPM_TIMEOUT_USECS_MIN, TPM_TIMEOUT_USECS_MAX);
>   } while (time_before(jiffies, stop));
>   return -EBUSY;
>  }

[PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Nayna Jain]

The TPM burstcount and status commands are supposed to return very
quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
directly.

After this change, performance on a TPM 1.2 with an 8 byte burstcount for
1000 extends improved from ~10.7 sec to ~7 sec.

[1] From TCG Specification "TCG PC Client Specific TPM Interface
Specification (TIS), Family 1.2":

"NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
take 84 us, which is a long time to stall the CPU. Chipsets may not be
designed to post this much data to LPC; therefore, the CPU itself is
stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
even if the TPM_STS_x.burstCount field is a high value, software SHOULD
be interruptible during this period."

[2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
(PTP) Specification":

"It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
84 us. Chipsets may not be designed to post this much data to LPC;
therefore, the CPU itself is stalled for much of this time. Sending 1 kB
would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
high value, software should be interruptible during this period. For SPI,
assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
to move 256B of data. Sending 1kB would take about 500 usec. If the
transactions are done using 4 bytes at a time, then it would take about
1 msec. to transfer 1kB of data."

Signed-off-by: Nayna Jain 
---
 drivers/char/tpm/tpm.h  | 4 +++-
 drivers/char/tpm/tpm_tis_core.c | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 7e797377e1eb..f0e4d290c347 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -54,7 +54,9 @@ enum tpm_timeout {
TPM_TIMEOUT = 5,/* msecs */
TPM_TIMEOUT_RETRY = 100, /* msecs */
TPM_TIMEOUT_RANGE_US = 300, /* usecs */
-   TPM_TIMEOUT_POLL = 1/* msecs */
+   TPM_TIMEOUT_POLL = 1,   /* msecs */
+   TPM_TIMEOUT_USECS_MIN = 100,  /* usecs */
+   TPM_TIMEOUT_USECS_MAX = 500  /* usecs */
 };
 
 /* TPM addresses */
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 021e6b68f2db..5bba5c662423 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -84,7 +84,8 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
}
} else {
do {
-   tpm_msleep(TPM_TIMEOUT_POLL);
+   usleep_range(TPM_TIMEOUT_USECS_MIN,
+   TPM_TIMEOUT_USECS_MAX);
status = chip->ops->status(chip);
if ((status & mask) == mask)
return 0;
@@ -226,7 +227,7 @@ static int get_burstcount(struct tpm_chip *chip)
burstcnt = (value >> 8) & 0x;
if (burstcnt)
return burstcnt;
-   tpm_msleep(TPM_TIMEOUT_POLL);
+   usleep_range(TPM_TIMEOUT_USECS_MIN, TPM_TIMEOUT_USECS_MAX);
} while (time_before(jiffies, stop));
return -EBUSY;
 }
-- 
2.13.3

[PATCH v2 2/2] tpm: reduce polling time to usecs for even finer granularity

[Nayna Jain]

The TPM burstcount and status commands are supposed to return very
quickly [1][2]. This patch further reduces the TPM poll sleep time to usecs
in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
directly.

After this change, performance on a TPM 1.2 with an 8 byte burstcount for
1000 extends improved from ~10.7 sec to ~7 sec.

[1] From TCG Specification "TCG PC Client Specific TPM Interface
Specification (TIS), Family 1.2":

"NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
take 84 us, which is a long time to stall the CPU. Chipsets may not be
designed to post this much data to LPC; therefore, the CPU itself is
stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
even if the TPM_STS_x.burstCount field is a high value, software SHOULD
be interruptible during this period."

[2] From TCG Specification 2.0, "TCG PC Client Platform TPM Profile
(PTP) Specification":

"It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
84 us. Chipsets may not be designed to post this much data to LPC;
therefore, the CPU itself is stalled for much of this time. Sending 1 kB
would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
high value, software should be interruptible during this period. For SPI,
assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
to move 256B of data. Sending 1kB would take about 500 usec. If the
transactions are done using 4 bytes at a time, then it would take about
1 msec. to transfer 1kB of data."

Signed-off-by: Nayna Jain 
---
 drivers/char/tpm/tpm.h  | 4 +++-
 drivers/char/tpm/tpm_tis_core.c | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 7e797377e1eb..f0e4d290c347 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -54,7 +54,9 @@ enum tpm_timeout {
TPM_TIMEOUT = 5,/* msecs */
TPM_TIMEOUT_RETRY = 100, /* msecs */
TPM_TIMEOUT_RANGE_US = 300, /* usecs */
-   TPM_TIMEOUT_POLL = 1/* msecs */
+   TPM_TIMEOUT_POLL = 1,   /* msecs */
+   TPM_TIMEOUT_USECS_MIN = 100,  /* usecs */
+   TPM_TIMEOUT_USECS_MAX = 500  /* usecs */
 };
 
 /* TPM addresses */
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 021e6b68f2db..5bba5c662423 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -84,7 +84,8 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
}
} else {
do {
-   tpm_msleep(TPM_TIMEOUT_POLL);
+   usleep_range(TPM_TIMEOUT_USECS_MIN,
+   TPM_TIMEOUT_USECS_MAX);
status = chip->ops->status(chip);
if ((status & mask) == mask)
return 0;
@@ -226,7 +227,7 @@ static int get_burstcount(struct tpm_chip *chip)
burstcnt = (value >> 8) & 0x;
if (burstcnt)
return burstcnt;
-   tpm_msleep(TPM_TIMEOUT_POLL);
+   usleep_range(TPM_TIMEOUT_USECS_MIN, TPM_TIMEOUT_USECS_MAX);
} while (time_before(jiffies, stop));
return -EBUSY;
 }
-- 
2.13.3