Re: [PATCH 4/6] drm/msm/a7xx: Initialize a750 "software fuse"

Connor Abbott
2024-04-26T12:35:33Z

On Fri, Apr 26, 2024 at 12:02 AM Dmitry Baryshkov
<dmitry.baryshkov@linaro.org> wrote:
>
> On Thu, 25 Apr 2024 at 16:44, Connor Abbott <cwabbott0@gmail.com> wrote:
> >
> > On all Qualcomm platforms with a7xx GPUs, qcom_scm provides a method to
> > initialize cx_mem. Copy this from downstream (minus BCL which we
> > currently don't support). On a750, this includes a new "fuse" register
> > which can be used by qcom_scm to fuse off certain features like
> > raytracing in software. The fuse is default off, and is initialized by
> > calling the method. Afterwards we have to read it to find out which
> > features were enabled.
> >
> > Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
> > ---
> > drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 89 ++++++++++++++++++++++++-
> > drivers/gpu/drm/msm/adreno/adreno_gpu.h | 2 +
> > 2 files changed, 90 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > index cf0b1de1c071..fb2722574ae5 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > @@ -10,6 +10,7 @@
> >
> > #include <linux/bitfield.h>
> > #include <linux/devfreq.h>
> > +#include <linux/firmware/qcom/qcom_scm.h>
> > #include <linux/pm_domain.h>
> > #include <linux/soc/qcom/llcc-qcom.h>
> >
> > @@ -1686,7 +1687,8 @@ static int a6xx_zap_shader_init(struct msm_gpu *gpu)
> > A6XX_RBBM_INT_0_MASK_RBBM_HANG_DETECT | \
> > A6XX_RBBM_INT_0_MASK_UCHE_OOB_ACCESS | \
> > A6XX_RBBM_INT_0_MASK_UCHE_TRAP_INTR | \
> > - A6XX_RBBM_INT_0_MASK_TSBWRITEERROR)
> > + A6XX_RBBM_INT_0_MASK_TSBWRITEERROR | \
> > + A6XX_RBBM_INT_0_MASK_SWFUSEVIOLATION)
> >
> > #define A7XX_APRIV_MASK (A6XX_CP_APRIV_CNTL_ICACHE | \
> > A6XX_CP_APRIV_CNTL_RBFETCH | \
> > @@ -2356,6 +2358,26 @@ static void a6xx_fault_detect_irq(struct msm_gpu *gpu)
> > kthread_queue_work(gpu->worker, &gpu->recover_work);
> > }
> >
> > +static void a7xx_sw_fuse_violation_irq(struct msm_gpu *gpu)
> > +{
> > + u32 status;
> > +
> > + status = gpu_read(gpu, REG_A7XX_RBBM_SW_FUSE_INT_STATUS);
> > + gpu_write(gpu, REG_A7XX_RBBM_SW_FUSE_INT_MASK, 0);
> > +
> > + dev_err_ratelimited(&gpu->pdev->dev, "SW fuse violation status=%8.8x\n", status);
> > +
> > + /* Ignore FASTBLEND violations, because the HW will silently fall back
> > + * to legacy blending.
> > + */
> > + if (status & (A7XX_CX_MISC_SW_FUSE_VALUE_RAYTRACING |
> > + A7XX_CX_MISC_SW_FUSE_VALUE_LPAC)) {
> > + del_timer(&gpu->hangcheck_timer);
> > +
> > + kthread_queue_work(gpu->worker, &gpu->recover_work);
> > + }
> > +}
> > +
> > static irqreturn_t a6xx_irq(struct msm_gpu *gpu)
> > {
> > struct msm_drm_private *priv = gpu->dev->dev_private;
> > @@ -2384,6 +2406,9 @@ static irqreturn_t a6xx_irq(struct msm_gpu *gpu)
> > if (status & A6XX_RBBM_INT_0_MASK_UCHE_OOB_ACCESS)
> > dev_err_ratelimited(&gpu->pdev->dev, "UCHE | Out of bounds access\n");
> >
> > + if (status & A6XX_RBBM_INT_0_MASK_SWFUSEVIOLATION)
> > + a7xx_sw_fuse_violation_irq(gpu);
> > +
> > if (status & A6XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS)
> > msm_gpu_retire(gpu);
> >
> > @@ -2525,6 +2550,60 @@ static void a6xx_llc_slices_init(struct platform_device *pdev,
> > a6xx_gpu->llc_mmio = ERR_PTR(-EINVAL);
> > }
> >
> > +static int a7xx_cx_mem_init(struct a6xx_gpu *a6xx_gpu)
> > +{
> > + struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
> > + struct msm_gpu *gpu = &adreno_gpu->base;
> > + u32 gpu_req = QCOM_SCM_GPU_ALWAYS_EN_REQ;
> > + u32 fuse_val;
> > + int ret;
> > +
> > + if (adreno_is_a740(adreno_gpu)) {
> > + /* Raytracing is always enabled on a740 */
> > + adreno_gpu->has_ray_tracing = true;
> > + }
> > +
> > + if (!qcom_scm_is_available()) {
> > + /* Assume that if qcom scm isn't available, that whatever
> > + * replacement allows writing the fuse register ourselves.
> > + * Users of alternative firmware need to make sure this
> > + * register is writeable or indicate that it's not somehow.
> > + * Print a warning because if you mess this up you're about to
> > + * crash horribly.
> > + */
> > + if (adreno_is_a750(adreno_gpu)) {
> > + dev_warn_once(gpu->dev->dev,
> > + "SCM is not available, poking fuse register\n");
> > + a6xx_llc_write(a6xx_gpu, REG_A7XX_CX_MISC_SW_FUSE_VALUE,
> > + A7XX_CX_MISC_SW_FUSE_VALUE_RAYTRACING |
> > + A7XX_CX_MISC_SW_FUSE_VALUE_FASTBLEND |
> > + A7XX_CX_MISC_SW_FUSE_VALUE_LPAC);
> > + adreno_gpu->has_ray_tracing = true;
> > + }
> > +
> > + return 0;
> > + }
> > +
> > + if (adreno_is_a750(adreno_gpu))
>
> Most of the function is under the if (adreno_is_a750) conditions. Can
> we invert the logic and add a single block of if(adreno_is_a750) and
> then place all the code underneath?

You mean to duplicate the qcom_scm_is_available check and qcom_scm_

>
> > + gpu_req |= QCOM_SCM_GPU_TSENSE_EN_REQ;
> > +
> > + ret = qcom_scm_gpu_init_regs(gpu_req);
> > + if (ret)
> > + return ret;
> > +
> > + /* On a750 raytracing may be disabled by the firmware, find out whether
> > + * that's the case. The scm call above sets the fuse register.
> > + */
> > + if (adreno_is_a750(adreno_gpu)) {
> > + fuse_val = a6xx_llc_read(a6xx_gpu, REG_A7XX_CX_MISC_SW_FUSE_VALUE);
>
> This register isn't accessible with the current sm8650.dtsi. Since DT
> and driver are going through different trees, please add safety guards
> here, so that the driver doesn't crash if used with older dtsi

I don't see how this is an issue. msm-next is currently based on 6.9,
which doesn't have the GPU defined in sm8650.dtsi. AFAIK patches 1 and
2 will have to go through the linux-arm-msm tree, which will have to
be merged into msm-next before this patch lands there, so there will
never be any breakage.

> (not to mention that dts is considered to be an ABI and newer kernels
> are supposed not to break with older DT files).

That policy only applies to released kernels, so that's irrelevant here.

>
> > + adreno_gpu->has_ray_tracing =
> > + !!(fuse_val & A7XX_CX_MISC_SW_FUSE_VALUE_RAYTRACING);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +
> > #define GBIF_CLIENT_HALT_MASK BIT(0)
> > #define GBIF_ARB_HALT_MASK BIT(1)
> > #define VBIF_XIN_HALT_CTRL0_MASK GENMASK(3, 0)
> > @@ -3094,6 +3173,14 @@ struct msm_gpu *a6xx_gpu_init(struct drm_device *dev)
> > return ERR_PTR(ret);
> > }
> >
> > + if (adreno_is_a7xx(adreno_gpu)) {
> > + ret = a7xx_cx_mem_init(a6xx_gpu);
> > + if (ret) {
> > + a6xx_destroy(&(a6xx_gpu->base.base));
> > + return ERR_PTR(ret);
> > + }
> > + }
> > +
> > if (gpu->aspace)
> > msm_mmu_set_fault_handler(gpu->aspace->mmu, gpu,
> > a6xx_fault_handler);
> > diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.h b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> > index 77526892eb8c..4180f3149dd8 100644
> > --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> > +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> > @@ -182,6 +182,8 @@ struct adreno_gpu {
> > */
> > const unsigned int *reg_offsets;
> > bool gmu_is_wrapper;
> > +
> > + bool has_ray_tracing;
> > };
> > #define to_adreno_gpu(x) container_of(x, struct adreno_gpu, base)
> >
> > --
> > 2.31.1
> >
>
>
> --
> With best wishes
> Dmitry