linux-kernel - Re: [PATCH] tpm: tis: Increase the default for timeouts B and C

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Message-ID: <Z-13xOebA3LvQQ-8@earth.li>
Date: Wed, 2 Apr 2025 18:45:40 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Michal Suchanek <msuchanek@...e.de>
Cc: Peter Huewe <peterhuewe@....de>, Jarkko Sakkinen <jarkko@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>, linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm: tis: Increase the default for timeouts B and C

On Wed, Apr 02, 2025 at 07:21:30PM +0200, Michal Suchanek wrote:
>With some Infineon chips the timeouts in tpm_tis_send_data (both B and
>C) can reach up to about 2250 ms.
>
>Extend the timeout duration to accommodate this.

The problem here is the bump of timeout_c is going to interact poorly 
with the Infineon errata workaround, as now we'll wait 4s instead of 
200ms to detect the stuck status change.

(Also shouldn't timeout_c already end up as 750ms, as it's 
max(TIS_SHORT_TIMEOUT, TPM2_TIMEOUT_C), and TIS_SHORT_TIMEOUT is 750 vs 
200 for TPM2_TIMEOUT_C? That doesn't seem to be borne out by your logs, 
nor my results.)

>Link: https://lore.kernel.org/linux-integrity/Z5pI07m0Muapyu9w@kitsune.suse.cz/
>Signed-off-by: Michal Suchanek <msuchanek@...e.de>
>---
>An alternative would be to add an entry to vendor_timeout_overrides but
>I do not know how to determine the chip IDs to put into this table.
>---
> drivers/char/tpm/tpm_tis_core.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
>index 970d02c337c7..1ff565be2175 100644
>--- a/drivers/char/tpm/tpm_tis_core.h
>+++ b/drivers/char/tpm/tpm_tis_core.h
>@@ -54,7 +54,7 @@ enum tis_int_flags {
> enum tis_defaults {
> 	TIS_MEM_LEN = 0x5000,
> 	TIS_SHORT_TIMEOUT = 750,	/* ms */
>-	TIS_LONG_TIMEOUT = 2000,	/* 2 sec */
>+	TIS_LONG_TIMEOUT = 4000,	/* 2 sec */
> 	TIS_TIMEOUT_MIN_ATML = 14700,	/* usecs */
> 	TIS_TIMEOUT_MAX_ATML = 15000,	/* usecs */
> };
>@@ -64,7 +64,7 @@ enum tis_defaults {
>  */
> #define TIS_TIMEOUT_A_MAX	max_t(int, TIS_SHORT_TIMEOUT, TPM2_TIMEOUT_A)
> #define TIS_TIMEOUT_B_MAX	max_t(int, TIS_LONG_TIMEOUT, TPM2_TIMEOUT_B)
>-#define TIS_TIMEOUT_C_MAX	max_t(int, TIS_SHORT_TIMEOUT, TPM2_TIMEOUT_C)
>+#define TIS_TIMEOUT_C_MAX	max_t(int, TIS_LONG_TIMEOUT, TPM2_TIMEOUT_C)
> #define TIS_TIMEOUT_D_MAX	max_t(int, TIS_SHORT_TIMEOUT, TPM2_TIMEOUT_D)
>
> #define	TPM_ACCESS(l)			(0x0000 | ((l) << 12))
>-- 
>2.47.1
>

J.

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