Suravee Suthikulpanit 63e9abe35d iommu/amd: Remove performance counter pre-initialization test ... [ Upstream commit 994d6608efe4a4c8834bdc5014c86f4bc6aceea6 ] In early AMD desktop/mobile platforms (during 2013), when the IOMMU Performance Counter (PMC) support was first introduced in commit 30861ddc9c ("perf/x86/amd: Add IOMMU Performance Counter resource management"), there was a HW bug where the counters could not be accessed. The result was reading of the counter always return zero. At the time, the suggested workaround was to add a test logic prior to initializing the PMC feature to check if the counters can be programmed and read back the same value. This has been working fine until the more recent desktop/mobile platforms start enabling power gating for the PMC, which prevents access to the counters. This results in the PMC support being disabled unnecesarily. Unfortunatly, there is no documentation of since which generation of hardware the original PMC HW bug was fixed. Although, it was fixed soon after the first introduction of the PMC. Base on this, we assume that the buggy platforms are less likely to be in used, and it should be relatively safe to remove this legacy logic. Link: https://lore.kernel.org/linux-iommu/alpine.LNX.3.20.13.2006030935570.3181@monopod.intra.ispras.ru/ Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753 Cc: Tj (Elloe Linux) <ml.linux@elloe.vision> Cc: Shuah Khan <skhan@linuxfoundation.org> Cc: Alexander Monakov <amonakov@ispras.ru> Cc: David Coe <david.coe@live.co.uk> Cc: Paul Menzel <pmenzel@molgen.mpg.de> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> Tested-by: Shuah Khan <skhan@linuxfoundation.org> Link: https://lore.kernel.org/r/20210409085848.3908-3-suravee.suthikulpanit@amd.com Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-05-19 10:12:56 +02:00
..
amd_iommu_types.h	iommu/amd: Use IVHD EFR for early initialization of IOMMU features	2021-02-03 23:28:50 +01:00
amd_iommu.h	iommu/amd: Use IVHD EFR for early initialization of IOMMU features	2021-02-03 23:28:50 +01:00
debugfs.c
init.c	iommu/amd: Remove performance counter pre-initialization test	2021-05-19 10:12:56 +02:00
iommu_v2.c	drm, iommu: Change type of pasid to u32	2020-09-17 19:21:16 +02:00
iommu.c	iommu/amd: Fix sleeping in atomic in increase_address_space()	2021-03-11 14:17:22 +01:00
Kconfig	iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE	2020-09-04 11:53:18 +02:00
Makefile	iommu/amd: Move Kconfig and Makefile bits down into amd directory	2020-07-29 14:15:36 +02:00
quirks.c