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

Lionel Landwerlin
2022-09-06T19:35:33Z

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()

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;

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 */
> };
>