linux-kernel - Re: [PATCH] drm/msm/a6xx: Remove unneeded GBIF unhalt

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Message-ID: <CAF6AEGuAT77aW+1Vh82oAoNCxSHsNNH5L8aRqsnVFV2CrDGaow@mail.gmail.com>
Date:   Wed, 5 Feb 2020 13:20:10 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Jordan Crouse <jcrouse@...eaurora.org>
Cc:     linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Sean Paul <sean@...rly.run>,
        Sharat Masetty <smasetty@...eaurora.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/msm/a6xx: Remove unneeded GBIF unhalt

On Tue, Feb 4, 2020 at 9:42 AM Jordan Crouse <jcrouse@...eaurora.org> wrote:
>
> Commit e812744c5f95 ("drm: msm: a6xx: Add support for A618") added a
> universal GBIF un-halt into a6xx_start(). This can cause problems for
> a630 targets which do not use GBIF and might have access protection
> enabled on the region now occupied by the GBIF registers.
>
> But it turns out that we didn't need to unhalt the GBIF in this path
> since the stop function already takes care of that after executing a flush
> but before turning off the headswitch. We should be confident that the
> GBIF is open for business when we restart the hardware.
>
> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>

Reviewed-by: Rob Clark <robdclark@...il.com>
Fixes: e812744c5f95 ("drm: msm: a6xx: Add support for A618")

> ---
>
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 12 ------------
>  1 file changed, 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index daf0780..e51c723 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -378,18 +378,6 @@ static int a6xx_hw_init(struct msm_gpu *gpu)
>         struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>         int ret;
>
> -       /*
> -        * During a previous slumber, GBIF halt is asserted to ensure
> -        * no further transaction can go through GPU before GPU
> -        * headswitch is turned off.
> -        *
> -        * This halt is deasserted once headswitch goes off but
> -        * incase headswitch doesn't goes off clear GBIF halt
> -        * here to ensure GPU wake-up doesn't fail because of
> -        * halted GPU transactions.
> -        */
> -       gpu_write(gpu, REG_A6XX_GBIF_HALT, 0x0);
> -
>         /* Make sure the GMU keeps the GPU on while we set it up */
>         a6xx_gmu_set_oob(&a6xx_gpu->gmu, GMU_OOB_GPU_SET);
>
> --
> 2.7.4