From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com ([134.134.136.65]:29116 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751158AbdBXRBR (ORCPT ); Fri, 24 Feb 2017 12:01:17 -0500 Date: Fri, 24 Feb 2017 19:01:00 +0200 From: Jarkko Sakkinen To: Mimi Zohar Cc: tpmdd-devel , Thomas@intel.com, Dan Morav , linux-fsdevel , linux-security-module , linux-ima-devel , Gleixner Subject: Re: [tpmdd-devel] [RFC PATCH] tpm: msleep() delays - replace with usleep_range() in i2c nuvoton driver Message-ID: <20170224170100.prwbcsffxdqjudc2@intel.com> References: <1487893578.3193.155.camel@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1487893578.3193.155.camel@linux.vnet.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Feb 23, 2017 at 06:46:18PM -0500, Mimi Zohar wrote: > 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. > > Signed-of-by: Mimi Zohar > Reviewed-by: Nayna Jain So why doesn't it go to level 0 with msleep()? I quickly skimmed through __mod_timer() and for me it looked like that level 0 would be calculated (when it is eventually called starting from msleep()). What did I miss? /Jarkko > --- > drivers/char/tpm/tpm_i2c_nuvoton.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c > index e3a9155ee671..da2508a6bc0c 100644 > --- a/drivers/char/tpm/tpm_i2c_nuvoton.c > +++ b/drivers/char/tpm/tpm_i2c_nuvoton.c > @@ -49,9 +49,9 @@ > */ > #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 OF_IS_TPM2 ((void *)1) > #define I2C_IS_TPM2 1 > @@ -123,7 +123,7 @@ static s32 i2c_nuvoton_write_status(struct i2c_client *client, u8 data) > /* 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 + 300); > } > return status; > } > @@ -160,7 +160,7 @@ static int i2c_nuvoton_get_burstcount(struct i2c_client *client, > 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 + 300); > } while (time_before(jiffies, stop)); > > return burst_count; > @@ -203,13 +203,15 @@ static int i2c_nuvoton_wait_for_stat(struct tpm_chip *chip, u8 mask, u8 value, > 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 + 300); > else > - msleep(TPM_I2C_RETRY_DELAY_LONG); > + usleep_range(TPM_I2C_RETRY_DELAY_LONG, > + TPM_I2C_RETRY_DELAY_LONG + 300); > status_valid = i2c_nuvoton_check_status(chip, mask, > value); > if (status_valid) > -- > 2.9.3 > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > _______________________________________________ > tpmdd-devel mailing list > tpmdd-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/tpmdd-devel