| Message ID | 20180417131246.434-3-nayna@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <nayna@linux.vnet.ibm.com> Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > --- > 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) & 0xFFFF; > 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; > } -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 <nayna@linux.vnet.ibm.com> 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.sakkinen@linux.intel.com> /Jarkko -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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) & 0xFFFF; 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; }
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 <nayna@linux.vnet.ibm.com> --- drivers/char/tpm/tpm.h | 4 +++- drivers/char/tpm/tpm_tis_core.c | 5 +++-- 2 files changed, 6 insertions(+), 3 deletions(-)