Re: [PATCH v2 1/2] drm/msm/adreno: Introduce ADRENO_QUIRK_NO_SYSCACHE

[Konrad Dybcio]

On 25.11.2024 5:33 PM, Akhil P Oommen wrote:
> There are a few chipsets which don't have system cache a.k.a LLC.
> Currently, the assumption in the driver is that the system cache
> availability correlates with the presence of GMU or RPMH, which
> is not true. For instance, Snapdragon 6 Gen 1 has RPMH and a GPU
> with a full blown GMU, but doesnot have a system cache. So,
> introduce an Adreno Quirk flag to check support for system cache
> instead of using gmu_wrapper flag.
> 
> Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_catalog.c | 3 ++-
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c     | 7 +------
>  drivers/gpu/drm/msm/adreno/adreno_gpu.h   | 1 +
>  3 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
> index 0c560e84ad5a..5e389f6b8b8a 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
> @@ -682,6 +682,7 @@ static const struct adreno_info a6xx_gpus[] = {
>  		},
>  		.gmem = (SZ_128K + SZ_4K),
>  		.inactive_period = DRM_MSM_INACTIVE_PERIOD,
> +		.quirks = ADRENO_QUIRK_NO_SYSCACHE,
>  		.init = a6xx_gpu_init,
>  		.zapfw = "a610_zap.mdt",
>  		.a6xx = &(const struct a6xx_info) {
> @@ -1331,7 +1332,7 @@ static const struct adreno_info a7xx_gpus[] = {
>  		},
>  		.gmem = SZ_128K,
>  		.inactive_period = DRM_MSM_INACTIVE_PERIOD,
> -		.quirks = ADRENO_QUIRK_HAS_HW_APRIV,
> +		.quirks = ADRENO_QUIRK_HAS_HW_APRIV | ADRENO_QUIRK_NO_SYSCACHE,
>  		.init = a6xx_gpu_init,
>  		.zapfw = "a702_zap.mbn",
>  		.a6xx = &(const struct a6xx_info) {

+a619_holi

> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 019610341df1..a8b928d0f320 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1863,10 +1863,6 @@ static void a7xx_llc_activate(struct a6xx_gpu *a6xx_gpu)
>  
>  static void a6xx_llc_slices_destroy(struct a6xx_gpu *a6xx_gpu)
>  {
> -	/* No LLCC on non-RPMh (and by extension, non-GMU) SoCs */
> -	if (adreno_has_gmu_wrapper(&a6xx_gpu->base))
> -		return;
> -
>  	llcc_slice_putd(a6xx_gpu->llc_slice);
>  	llcc_slice_putd(a6xx_gpu->htw_llc_slice);
>  }
> @@ -1876,8 +1872,7 @@ static void a6xx_llc_slices_init(struct platform_device *pdev,
>  {
>  	struct device_node *phandle;
>  
> -	/* No LLCC on non-RPMh (and by extension, non-GMU) SoCs */
> -	if (adreno_has_gmu_wrapper(&a6xx_gpu->base))
> +	if (a6xx_gpu->base.info->quirks & ADRENO_QUIRK_NO_SYSCACHE)
>  		return;

I think A612 is the "quirky" one here.. it has some sort of a GMU,
but we're choosing not to implement it. maybe a check for

if (adreno_has_gmu_wrapper && !adreno_is_a612)

would be clearer here, with a comment that RGMU support is not
implemented



But going further, I'm a bit concerned about dt-bindings.. If we
implement RGMU on the driver side in the future, that will require
DT changes which will make the currently proposed description invalid.

I think a better angle would be to add a adreno_has_rgmu() func with
a qcom,adreno-rgmu compatible and plumb it correctly from the get-go.

This way, we can avoid this syscache quirk as well.

Konrad