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Date:   Fri,  8 Jan 2021 17:56:01 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     robdclark@...il.com
Cc:     airlied@...ux.ie, airlied@...hat.com, akhilpo@...eaurora.org,
        angelogioacchino.delregno@...ainline.org,
        bjorn.andersson@...aro.org, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        jcrouse@...eaurora.org, jonathan@...ek.ca,
        konrad.dybcio@...ainline.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, phone-devel@...r.kernel.org,
        saiprakash.ranjan@...eaurora.org, sean@...rly.run,
        shawn.guo@...aro.org, smasetty@...eaurora.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH] drm/msm: Only enable A6xx LLCC code on A6xx

Hi Rob, Konrad,

On 2021-01-07 22:56, Rob Clark wrote:
> On Wed, Jan 6, 2021 at 8:50 PM Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>>
>> On 2021-01-05 01:00, Konrad Dybcio wrote:
>> > Using this code on A5xx (and probably older too) causes a
>> > smmu bug.
>> >
>> > Fixes: 474dadb8b0d5 ("drm/msm/a6xx: Add support for using system
>> > cache(LLC)")
>> > Signed-off-by: Konrad Dybcio <konrad.dybcio@...ainline.org>
>> > Tested-by: AngeloGioacchino Del Regno
>> > <angelogioacchino.delregno@...ainline.org>
>> > ---
>>
>> Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>>
>> >  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 21 ++++++++++++---------
>> >  drivers/gpu/drm/msm/adreno/adreno_gpu.h |  5 +++++
>> >  2 files changed, 17 insertions(+), 9 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> > b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> > index 6cf9975e951e..f09175698827 100644
>> > --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> > +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>> > @@ -191,8 +191,6 @@ adreno_iommu_create_address_space(struct msm_gpu
>> > *gpu,
>> >               struct platform_device *pdev)
>> >  {
>> >       struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>> > -     struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>> > -     struct io_pgtable_domain_attr pgtbl_cfg;
>> >       struct iommu_domain *iommu;
>> >       struct msm_mmu *mmu;
> >       struct msm_gem_address_space *aspace;
>> > @@ -202,13 +200,18 @@ adreno_iommu_create_address_space(struct msm_gpu
>> > *gpu,
>> >       if (!iommu)
>> >               return NULL;
>> >
>> > -     /*
>> > -      * This allows GPU to set the bus attributes required to use system
>> > -      * cache on behalf of the iommu page table walker.
>> > -      */
>> > -     if (!IS_ERR(a6xx_gpu->htw_llc_slice)) {
>> > -             pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_ARM_OUTER_WBWA;
>> > -             iommu_domain_set_attr(iommu, DOMAIN_ATTR_IO_PGTABLE_CFG,
>> > &pgtbl_cfg);
>> > +
>> > +     if (adreno_is_a6xx(adreno_gpu)) {
>> > +             struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>> > +             struct io_pgtable_domain_attr pgtbl_cfg;
>> > +             /*
>> > +             * This allows GPU to set the bus attributes required to use system
>> > +             * cache on behalf of the iommu page table walker.
>> > +             */
>> > +             if (!IS_ERR(a6xx_gpu->htw_llc_slice)) {
>> > +                     pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_ARM_OUTER_WBWA;
>> > +                     iommu_domain_set_attr(iommu, DOMAIN_ATTR_IO_PGTABLE_CFG,
>> > &pgtbl_cfg);
>> > +             }
>
> I'm applying for -fixes as this is an obvious problem..  But kinda
> thinking that we should try to move it into an a6xx specific
> create_address_space() (or wrapper for the generic fxn)
>
> Sai/Jordan, could I talk one of you into trying to clean this up
> better for next cycle?
>

Looking more closely(sorry I should have before), the quirk setting
is already guarded by htw_llc_slice check but what is happening here is
that check is not proper when LLCC is disabled i.e., CONFIG_QCOM_LLCC=n.
When LLCC is disabled, htw_llc_slice is set to NULL and the !IS_ERR
check passes because it doesn't take care of NULL and quirk is
set causing bugs. So the proper fix would be to use IS_ERR_OR_NULL for
the check.

Konrad, can you please test this below change without your change?

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index 130661898546..3b798e883f82 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -1117,7 +1117,7 @@ static void a6xx_llc_slices_init(struct platform_device *pdev,
        a6xx_gpu->llc_slice = llcc_slice_getd(LLCC_GPU);
        a6xx_gpu->htw_llc_slice = llcc_slice_getd(LLCC_GPUHTW);

-       if (IS_ERR(a6xx_gpu->llc_slice) && IS_ERR(a6xx_gpu->htw_llc_slice))
+       if (IS_ERR_OR_NULL(a6xx_gpu->llc_slice) && IS_ERR_OR_NULL(a6xx_gpu->htw_llc_slice))
                a6xx_gpu->llc_mmio = ERR_PTR(-EINVAL);
 }

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index 6cf9975e951e..dbd5cacddb9c 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -206,7 +206,7 @@ adreno_iommu_create_address_space(struct msm_gpu *gpu,
         * This allows GPU to set the bus attributes required to use system
         * cache on behalf of the iommu page table walker.
         */
-       if (!IS_ERR(a6xx_gpu->htw_llc_slice)) {
+       if (!IS_ERR_OR_NULL(a6xx_gpu->htw_llc_slice)) {
                pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_ARM_OUTER_WBWA;
                iommu_domain_set_attr(iommu, DOMAIN_ATTR_IO_PGTABLE_CFG, &pgtbl_cfg);
        }


Thanks,
Sai

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