Re: [Intel-gfx] [PATCH 02/19] drm/i915/perf: Add OA formats for DG2

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

On 06/09/2022 22:46, Umesh Nerlige Ramappa wrote:
> On Tue, Sep 06, 2022 at 10:35:16PM +0300, Lionel Landwerlin wrote:
>> On 23/08/2022 23:41, Umesh Nerlige Ramappa wrote:
>>> Add new OA formats for DG2. Some of the newer OA formats are not
>>> multples of 64 bytes and are not powers of 2. For those formats, adjust
>>> hw_tail accordingly when checking for new reports.
>>>
>>> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramampa@intel.com>
>>
>> Apart from the coding style issue :
>>
>>
>> Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>>
>>
>>> ---
>>>  drivers/gpu/drm/i915/i915_perf.c | 63 ++++++++++++++++++++------------
>>>  include/uapi/drm/i915_drm.h      |  6 +++
>>>  2 files changed, 46 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_perf.c 
>>> b/drivers/gpu/drm/i915/i915_perf.c
>>> index 735244a3aedd..c8331b549d31 100644
>>> --- a/drivers/gpu/drm/i915/i915_perf.c
>>> +++ b/drivers/gpu/drm/i915/i915_perf.c
>>> @@ -306,7 +306,8 @@ static u32 i915_oa_max_sample_rate = 100000;
>>>  /* XXX: beware if future OA HW adds new report formats that the 
>>> current
>>>   * code assumes all reports have a power-of-two size and ~(size - 
>>> 1) can
>>> - * be used as a mask to align the OA tail pointer.
>>> + * be used as a mask to align the OA tail pointer. In some of the
>>> + * formats, R is used to denote reserved field.
>>>   */
>>>  static const struct i915_oa_format oa_formats[I915_OA_FORMAT_MAX] = {
>>>      [I915_OA_FORMAT_A13]        = { 0, 64 },
>>> @@ -320,6 +321,10 @@ static const struct i915_oa_format 
>>> oa_formats[I915_OA_FORMAT_MAX] = {
>>>      [I915_OA_FORMAT_A12]            = { 0, 64 },
>>>      [I915_OA_FORMAT_A12_B8_C8]        = { 2, 128 },
>>>      [I915_OA_FORMAT_A32u40_A4u32_B8_C8] = { 5, 256 },
>>> +    [I915_OAR_FORMAT_A32u40_A4u32_B8_C8]    = { 5, 256 },
>>> +    [I915_OA_FORMAT_A24u40_A14u32_B8_C8]    = { 5, 256 },
>>> +    [I915_OAR_FORMAT_A36u64_B8_C8]        = { 1, 384 },
>>> +    [I915_OA_FORMAT_A38u64_R2u64_B8_C8]    = { 1, 448 },
>>>  };
>>>  #define SAMPLE_OA_REPORT      (1<<0)
>>> @@ -467,6 +472,7 @@ static bool oa_buffer_check_unlocked(struct 
>>> i915_perf_stream *stream)
>>>      bool pollin;
>>>      u32 hw_tail;
>>>      u64 now;
>>> +    u32 partial_report_size;
>>>      /* We have to consider the (unlikely) possibility that read() 
>>> errors
>>>       * could result in an OA buffer reset which might reset the 
>>> head and
>>> @@ -476,10 +482,16 @@ static bool oa_buffer_check_unlocked(struct 
>>> i915_perf_stream *stream)
>>>      hw_tail = stream->perf->ops.oa_hw_tail_read(stream);
>>> -    /* The tail pointer increases in 64 byte increments,
>>> -     * not in report_size steps...
>>> +    /* The tail pointer increases in 64 byte increments, whereas 
>>> report
>>> +     * sizes need not be integral multiples or 64 or powers of 2.
>>> +     * Compute potentially partially landed report in the OA buffer
>>>       */
>>> -    hw_tail &= ~(report_size - 1);
>>> +    partial_report_size = OA_TAKEN(hw_tail, stream->oa_buffer.tail);
>>> +    partial_report_size %= report_size;
>>> +
>>> +    /* Subtract partial amount off the tail */
>>> +    hw_tail = gtt_offset + ((hw_tail - partial_report_size) &
>>> +                (stream->oa_buffer.vma->size - 1));
>>>      now = ktime_get_mono_fast_ns();
>>> @@ -601,6 +613,8 @@ static int append_oa_sample(struct 
>>> i915_perf_stream *stream,
>>>  {
>>>      int report_size = stream->oa_buffer.format_size;
>>>      struct drm_i915_perf_record_header header;
>>> +    int report_size_partial;
>>> +    u8 *oa_buf_end;
>>>      header.type = DRM_I915_PERF_RECORD_SAMPLE;
>>>      header.pad = 0;
>>> @@ -614,7 +628,19 @@ static int append_oa_sample(struct 
>>> i915_perf_stream *stream,
>>>          return -EFAULT;
>>>      buf += sizeof(header);
>>> -    if (copy_to_user(buf, report, report_size))
>>> +    oa_buf_end = stream->oa_buffer.vaddr +
>>> +             stream->oa_buffer.vma->size;
>>> +    report_size_partial = oa_buf_end - report;
>>> +
>>> +    if (report_size_partial < report_size) {
>>> +        if(copy_to_user(buf, report, report_size_partial))
>>> +            return -EFAULT;
>>> +        buf += report_size_partial;
>>> +
>>> +        if(copy_to_user(buf, stream->oa_buffer.vaddr,
>>> +                report_size - report_size_partial))
>>> +            return -EFAULT;
>>
>> I think the coding style requires you to use if () not if()
>>
>
> Will fix.
>
>>
>> Just a suggestion : you could make this code deal with the partial 
>> bit as the main bit of the function :
>>
>>
>> oa_buf_end = stream->oa_buffer.vaddr +
>>          stream->oa_buffer.vma->size;
>>
>> report_size_partial = oa_buf_end - report;
>>
>> if (copy_to_user(buf, report, report_size_partial))
>>     return -EFAULT;
>> buf += report_size_partial;
>
> This ^ may not work because append_oa_sample is appending exactly one 
> report to the user buffer, whereas the above may append more than one.
>
> Thanks,
> Umesh


Ah I see, thanks for pointing this out.

-Lionel


>
>>
>> if (report_size_partial < report_size &&
>>    copy_to_user(buf, stream->oa_buffer.vaddr,
>>         report_size - report_size_partial))
>>     return -EFAULT;
>> buf += report_size - report_size_partial;
>>
>>
>>> +    } else if (copy_to_user(buf, report, report_size))
>>>          return -EFAULT;
>>>      (*offset) += header.size;
>>> @@ -684,8 +710,8 @@ static int gen8_append_oa_reports(struct 
>>> i915_perf_stream *stream,
>>>       * all a power of two).
>>>       */
>>>      if (drm_WARN_ONCE(&uncore->i915->drm,
>>> -              head > OA_BUFFER_SIZE || head % report_size ||
>>> -              tail > OA_BUFFER_SIZE || tail % report_size,
>>> +              head > stream->oa_buffer.vma->size ||
>>> +              tail > stream->oa_buffer.vma->size,
>>>                "Inconsistent OA buffer pointers: head = %u, tail = 
>>> %u\n",
>>>                head, tail))
>>>          return -EIO;
>>> @@ -699,22 +725,6 @@ static int gen8_append_oa_reports(struct 
>>> i915_perf_stream *stream,
>>>          u32 ctx_id;
>>>          u32 reason;
>>> -        /*
>>> -         * All the report sizes factor neatly into the buffer
>>> -         * size so we never expect to see a report split
>>> -         * between the beginning and end of the buffer.
>>> -         *
>>> -         * Given the initial alignment check a misalignment
>>> -         * here would imply a driver bug that would result
>>> -         * in an overrun.
>>> -         */
>>> -        if (drm_WARN_ON(&uncore->i915->drm,
>>> -                (OA_BUFFER_SIZE - head) < report_size)) {
>>> -            drm_err(&uncore->i915->drm,
>>> -                "Spurious OA head ptr: non-integral report offset\n");
>>> -            break;
>>> -        }
>>> -
>>>          /*
>>>           * The reason field includes flags identifying what
>>>           * triggered this specific report (mostly timer
>>> @@ -4513,6 +4523,13 @@ static void oa_init_supported_formats(struct 
>>> i915_perf *perf)
>>>          oa_format_add(perf, I915_OA_FORMAT_C4_B8);
>>>          break;
>>> +    case INTEL_DG2:
>>> +        oa_format_add(perf, I915_OAR_FORMAT_A32u40_A4u32_B8_C8);
>>> +        oa_format_add(perf, I915_OA_FORMAT_A24u40_A14u32_B8_C8);
>>> +        oa_format_add(perf, I915_OAR_FORMAT_A36u64_B8_C8);
>>> +        oa_format_add(perf, I915_OA_FORMAT_A38u64_R2u64_B8_C8);
>>> +        break;
>>> +
>>>      default:
>>>          MISSING_CASE(platform);
>>>      }
>>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
>>> index 520ad2691a99..d20d723925b5 100644
>>> --- a/include/uapi/drm/i915_drm.h
>>> +++ b/include/uapi/drm/i915_drm.h
>>> @@ -2650,6 +2650,12 @@ enum drm_i915_oa_format {
>>>      I915_OA_FORMAT_A12_B8_C8,
>>>      I915_OA_FORMAT_A32u40_A4u32_B8_C8,
>>> +    /* DG2 */
>>> +    I915_OAR_FORMAT_A32u40_A4u32_B8_C8,
>>> +    I915_OA_FORMAT_A24u40_A14u32_B8_C8,
>>> +    I915_OAR_FORMAT_A36u64_B8_C8,
>>> +    I915_OA_FORMAT_A38u64_R2u64_B8_C8,
>>> +
>>>      I915_OA_FORMAT_MAX        /* non-ABI */
>>>  };
>>
>>