lkml.org 
[lkml]   [2023]   [Jun]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/5] perf: arm_cspmu: Support 32-bit accesses to 64-bit registers

Hi Robin,

On Thu, 1 Jun 2023, Robin Murphy wrote:
> On 2023-06-01 04:01, Ilkka Koskinen wrote:
>> Split the 64-bit register accesses if 64-bit access is not supported
>> by the PMU.
>>
>> Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
>> ---
>> drivers/perf/arm_cspmu/arm_cspmu.c | 8 ++++++--
>> drivers/perf/arm_cspmu/arm_cspmu.h | 1 +
>> 2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c
>> b/drivers/perf/arm_cspmu/arm_cspmu.c
>> index a3f1c410b417..88547a2b73e6 100644
>> --- a/drivers/perf/arm_cspmu/arm_cspmu.c
>> +++ b/drivers/perf/arm_cspmu/arm_cspmu.c
>> @@ -701,8 +701,12 @@ static void arm_cspmu_write_counter(struct perf_event
>> *event, u64 val)
>> if (use_64b_counter_reg(cspmu)) {
>> offset = counter_offset(sizeof(u64), event->hw.idx);
>> -
>> - writeq(val, cspmu->base1 + offset);
>> + if (!cspmu->impl.split_64bit_access) {
>
> Could we not just hang this off the 64-bit atomicity property to match the
> read path? It doesn't seem like there's much benefit in micro-optimising for
> whether the interconnect splits 64-bit accesses into 32-bit bursts vs. just
> not accepting them at all.

Sure, I was actually wondering if I could use it or if there could be
a really weird hw implementation. I'll change it.

>
>> + writeq(val, cspmu->base1 + offset);
>> + } else {
>> + writel(lower_32_bits(val), cspmu->base1 + offset);
>> + writel(upper_32_bits(val), cspmu->base1 + offset +
>> 4);
>
> lo_hi_writeq() - the header's already included for 32-bit build coverage, so
> we may as well put it to use :)

Oh, I have missed that function completely. I fix this too.

Cheers, Ilkka


> Thanks,
> Robin.
>
>> + }
>> } else {
>> offset = counter_offset(sizeof(u32), event->hw.idx);
>> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.h
>> b/drivers/perf/arm_cspmu/arm_cspmu.h
>> index 51323b175a4a..c0412cf2bd97 100644
>> --- a/drivers/perf/arm_cspmu/arm_cspmu.h
>> +++ b/drivers/perf/arm_cspmu/arm_cspmu.h
>> @@ -110,6 +110,7 @@ struct arm_cspmu_impl_ops {
>> /* Vendor/implementer descriptor. */
>> struct arm_cspmu_impl {
>> u32 pmiidr;
>> + bool split_64bit_access;
>> struct arm_cspmu_impl_ops ops;
>> void *ctx;
>> };
>

\
 
 \ /
  Last update: 2023-06-02 08:49    [W:0.077 / U:2.640 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site