Re: [Intel-gfx] [PATCH 1/3] i915/perf: Store a mask of valid OA formats for a platform

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Umesh Nerlige Ramappa (2021-02-02 07:54:15)
> Validity of an OA format is checked by using a sparse array of formats
> per gen. Instead maintain a mask of supported formats for a platform in
> the perf object.
> 
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_perf.c       | 64 +++++++++++++++++++++++++-
>  drivers/gpu/drm/i915/i915_perf_types.h | 16 +++++++
>  2 files changed, 79 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 112ba5f2ce90..973577fcad58 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -3524,6 +3524,19 @@ static u64 oa_exponent_to_ns(struct i915_perf *perf, int exponent)
>                                              2ULL << exponent);
>  }
>  
> +static __always_inline bool
> +oa_format_valid(struct i915_perf *perf, enum drm_i915_oa_format format)
> +{
> +       return !!(perf->format_mask[__format_index(format)] &
> +                 __format_bit(format));

!! is already provided by the implicit cast to (bool)

> +}
> +
> +static __always_inline void
> +oa_format_add(struct i915_perf *perf, enum drm_i915_oa_format format)
> +{
> +       perf->format_mask[__format_index(format)] |= __format_bit(format);
> +}
> +
>  /**
>   * read_properties_unlocked - validate + copy userspace stream open properties
>   * @perf: i915 perf instance
> @@ -3615,7 +3628,7 @@ static int read_properties_unlocked(struct i915_perf *perf,
>                                           value);
>                                 return -EINVAL;
>                         }
> -                       if (!perf->oa_formats[value].size) {
> +                       if (!oa_format_valid(perf, value)) {
>                                 DRM_DEBUG("Unsupported OA report format %llu\n",
>                                           value);
>                                 return -EINVAL;
> @@ -4259,6 +4272,53 @@ static struct ctl_table dev_root[] = {
>         {}
>  };
>  
> +static void oa_init_supported_formats(struct i915_perf *perf)
> +{
> +       struct drm_i915_private *i915 = perf->i915;
> +       enum intel_platform platform = INTEL_INFO(i915)->platform;
> +
> +       switch (platform) {
> +       case INTEL_HASWELL:
> +               oa_format_add(perf, I915_OA_FORMAT_A13);
> +               oa_format_add(perf, I915_OA_FORMAT_A13);
> +               oa_format_add(perf, I915_OA_FORMAT_A29);
> +               oa_format_add(perf, I915_OA_FORMAT_A13_B8_C8);
> +               oa_format_add(perf, I915_OA_FORMAT_B4_C8);
> +               oa_format_add(perf, I915_OA_FORMAT_A45_B8_C8);
> +               oa_format_add(perf, I915_OA_FORMAT_B4_C8_A16);
> +               oa_format_add(perf, I915_OA_FORMAT_C4_B8);
> +               break;
> +
> +       case INTEL_BROADWELL:
> +       case INTEL_CHERRYVIEW:
> +       case INTEL_SKYLAKE:
> +       case INTEL_BROXTON:
> +       case INTEL_KABYLAKE:
> +       case INTEL_GEMINILAKE:
> +       case INTEL_COFFEELAKE:
> +       case INTEL_COMETLAKE:
> +       case INTEL_CANNONLAKE:
> +       case INTEL_ICELAKE:
> +       case INTEL_ELKHARTLAKE:
> +       case INTEL_JASPERLAKE:
> +               oa_format_add(perf, I915_OA_FORMAT_A12);
> +               oa_format_add(perf, I915_OA_FORMAT_A12_B8_C8);
> +               oa_format_add(perf, I915_OA_FORMAT_A32u40_A4u32_B8_C8);
> +               oa_format_add(perf, I915_OA_FORMAT_C4_B8);
> +               break;

Ok, this looks as compact and readable as writing it as a bunch of
tables. I presume there's a reason you didn't just use generation rather
than platform.

switch (gen) {
case 7:
	haswell();
	break;
case 8 .. 11:
	broadwell();
	break;
case 12:
	tigerlake();
	break;
}
if you wanted to stick with a switch rather than an if-else tree for the
ranges.

Note you could equally do 
	case INTEL_BROADWELL .. INTEL_JASPERLAKE:
but I expect that to cause confusion for the reader.

> +       /**
> +        * Use a format mask to store the supported formats
> +        * for a platform.
> +        */
> +#define __fbits (BITS_PER_TYPE(u32))
> +#define __format_bit(__f) \
> +       BIT((__f) & (__fbits - 1))
> +
> +#define __format_index_shift (5)
> +#define __format_index(__f) \
> +       (((__f) & ~(__fbits - 1)) >> __format_index_shift)
> +
> +#define FORMAT_MASK_SIZE (((I915_OA_FORMAT_MAX - 1) / __fbits) + 1)
> +       u32 format_mask[FORMAT_MASK_SIZE];

This is just open-coding set_bit/test_bit

#define FORMAT_MASK_SIZE DIV_ROUND_UP(I915_OA_FORMAT_MAX - 1, BITS_PER_LONG)
unsigned long format_mask[FORMAT_MASK_SIZE];

static __always_inline bool
oa_format_valid(struct i915_perf *perf, enum drm_i915_oa_format format)
{
	return test_bit(format, perf->format_mask);
}

static __always_inline void
oa_format_add(struct i915_perf *perf, enum drm_i915_oa_format format)
{
	__set_bit(format, perf->format_mask);
}
-Chris
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