Messages in this thread | | | Date | Tue, 5 Sep 2023 15:51:00 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] perf: CXL: fix mismatched number of counters mask |
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On Tue, Sep 05, 2023 at 03:46:34PM +0100, Jonathan Cameron wrote: > On Tue, 5 Sep 2023 15:28:54 +0100 > Will Deacon <will@kernel.org> wrote: > > > On Tue, Sep 05, 2023 at 09:33:09PM +0900, Jeongtae Park wrote: > > > The number of Count Units field is described as 6 bits long > > > in the CXL 3.0 specification. However, its mask value was > > > only declared as 5 bits long. > > > > > > Signed-off-by: Jeongtae Park <jtp.park@samsung.com> > > > --- > > > drivers/perf/cxl_pmu.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/perf/cxl_pmu.c b/drivers/perf/cxl_pmu.c > > > index 0a8f597e695b..365d964b0f6a 100644 > > > --- a/drivers/perf/cxl_pmu.c > > > +++ b/drivers/perf/cxl_pmu.c > > > @@ -25,7 +25,7 @@ > > > #include "../cxl/pmu.h" > > > > > > #define CXL_PMU_CAP_REG 0x0 > > > -#define CXL_PMU_CAP_NUM_COUNTERS_MSK GENMASK_ULL(4, 0) > > > +#define CXL_PMU_CAP_NUM_COUNTERS_MSK GENMASK_ULL(5, 0) > > > #define CXL_PMU_CAP_COUNTER_WIDTH_MSK GENMASK_ULL(15, 8) > > > #define CXL_PMU_CAP_NUM_EVN_CAP_REG_SUP_MSK GENMASK_ULL(24, 20) > > > #define CXL_PMU_CAP_FILTERS_SUP_MSK GENMASK_ULL(39, 32) > > > > I don't have access to the CXL spec, but widening this mask looks like > > it puts us out-of-whack with CXL_PMU_MAX_COUNTERS. > > > > Did v3.0 of the spec bump the number of counters? If so, can you please > > check that this is a backwards-compatible change? > > CXL Performance monitors were only introduced in CXL 3.0 so not that.
Thanks for the information!
> The max value that register can take is 0x3f (0 based, so 64 counters == > CXL_PMU_MAX_COUNTERS) > So it should be 6 bits wide. I did some history digging and this isn't > even a draft spec / final spec issue - simple typo I guess.
Heh, I blame the heat as I thought this was extending to 7 bits for some reason. Sorry about that.
> Fix seems correct to me. > > Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
I'll pick it up, thanks again!
Will
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