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SubjectRe: [PATCH v7 4/4] perf/smmuv3: Enable HiSilicon Erratum 162001800 quirk
On Tue, Mar 26, 2019 at 03:17:53PM +0000, Shameer Kolothum wrote:
> HiSilicon erratum 162001800 describes the limitation of
> SMMUv3 PMCG implementation on HiSilicon Hip08 platforms.
>
> On these platforms, the PMCG event counter registers
> (SMMU_PMCG_EVCNTRn) are read only and as a result it
> is not possible to set the initial counter period value
> on event monitor start.
>
> To work around this, the current value of the counter
> is read and used for delta calculations. OEM information
> from ACPI header is used to identify the affected hardware
> platforms.
>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/acpi/arm64/iort.c | 16 ++++++++++++++-
> drivers/perf/arm_smmuv3_pmu.c | 48 ++++++++++++++++++++++++++++++++++++-------
> include/linux/acpi_iort.h | 1 +
> 3 files changed, 57 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index e2c9b26..4dc68de 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -1366,9 +1366,23 @@ static void __init arm_smmu_v3_pmcg_init_resources(struct resource *res,
> ACPI_EDGE_SENSITIVE, &res[2]);
> }
>
> +static struct acpi_platform_list pmcg_plat_info[] __initdata = {
> + /* HiSilicon Hip08 Platform */
> + {"HISI ", "HIP08 ", 0, ACPI_SIG_IORT, greater_than_or_equal, 0,

Passing integer constant 0 for the reason feels wrong to me. I'm going to
change it to "Erratum #162001800" and also add an entry to
silicon-errata.txt.

Please shout if that's not ok.

Will

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