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

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

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

>
>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 */
>>  };
>
>