linux-kernel - [PATCH v2] 2.6.27-rc3-mmotm tpm-correct-tpm-timeouts-to-jiffies-conversion-d820-fix.patch

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Message-ID: <11547.1218794163@turing-police.cc.vt.edu>
Date:	Fri, 15 Aug 2008 05:56:03 -0400
From:	Valdis.Kletnieks@...edu
To:	Marcin Obara <marcin_obara@...rs.sourceforge.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Marcel Selhorst <tpm@...horst.net>,
	Kylene Jo Hall <kjhall@...ibm.com>,
	tpmdd-devel@...ts.sourceforge.net
Subject: [PATCH v2] 2.6.27-rc3-mmotm  tpm-correct-tpm-timeouts-to-jiffies-conversion-d820-fix.patch

Patch tpm-correct-tpm-timeouts-to-jiffies-conversion reveals a bug in the
Broadcom BCM0102 TPM chipset used in the Dell Latitude D820 - although most of
the timeouts are returned in usecs as per the spec, one is apparently returned
in msecs, which results in a too-small value leading to a timeout when the code
treats it as usecs.  To prevent a regression, we check for the known too-short
value and adjust it to a value that makes things work.

Version 2: Clarify comment somewhat, fix if statement to properly deal with
variant HZ values.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@...edu>
cc: Marcin Obara <marcin_obara@...rs.sourceforge.net>

Index: linux-2.6.27-rc3-mmotm0814/drivers/char/tpm/tpm.c
===================================================================
--- linux-2.6.27-rc3-mmotm0814.orig/drivers/char/tpm/tpm.c	2008-08-15 02:19:58.000000000 -0400
+++ linux-2.6.27-rc3-mmotm0814/drivers/char/tpm/tpm.c	2008-08-15 05:44:48.000000000 -0400
@@ -557,6 +557,13 @@
 	    usecs_to_jiffies(be32_to_cpu
 			     (*((__be32 *) (data +
 					    TPM_GET_CAP_RET_UINT32_1_IDX))));
+	/* The Broadcom BCM0102 chipset in a Dell Latitude D820 gets the above
+	 * value wrong and apparently reports msecs rather than usecs. So we
+	 * fix up the resulting too-small TPM_SHORT value to make things work.
+	 */
+	if (chip->vendor.duration[TPM_SHORT] < (HZ/100))
+		chip->vendor.duration[TPM_SHORT] = HZ;
+
 	chip->vendor.duration[TPM_MEDIUM] =
 	    usecs_to_jiffies(be32_to_cpu
 			     (*((__be32 *) (data +


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