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SubjectRe: [PATCH 5/5] drm/msm/a6xx: Add support for using system cache(LLC)
On 2019-12-20 01:28, Jordan Crouse wrote:
> On Thu, Dec 19, 2019 at 06:44:46PM +0530, Sharat Masetty wrote:
>> The last level system cache can be partitioned to 32 different slices
>> of which GPU has two slices preallocated. One slice is used for
>> caching GPU
>> buffers and the other slice is used for caching the GPU SMMU
>> pagetables.
>> This patch talks to the core system cache driver to acquire the slice
>> handles,
>> configure the SCID's to those slices and activates and deactivates the
>> slices
>> upon GPU power collapse and restore.
>>
>> Some support from the IOMMU driver is also needed to make use of the
>> system cache. IOMMU_QCOM_SYS_CACHE is a buffer protection flag which
>> enables
>> caching GPU data buffers in the system cache with memory attributes
>> such
>> as outer cacheable, read-allocate, write-allocate for buffers. The GPU
>> then has the ability to override a few cacheability parameters which
>> it
>> does to override write-allocate to write-no-allocate as the GPU
>> hardware
>> does not benefit much from it.
>>
>> Similarly DOMAIN_ATTR_QCOM_SYS_CACHE is another domain level attribute
>> used by the IOMMU driver to set the right attributes to cache the
>> hardware
>> pagetables into the system cache.
>>
>> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
>> ---
>> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 122
>> +++++++++++++++++++++++++++++++++-
>> drivers/gpu/drm/msm/adreno/a6xx_gpu.h | 9 +++
>> drivers/gpu/drm/msm/msm_iommu.c | 13 ++++
>> drivers/gpu/drm/msm/msm_mmu.h | 3 +
>> 4 files changed, 146 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> index faff6ff..0c7fdee 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> @@ -9,6 +9,7 @@
>> #include "a6xx_gmu.xml.h"
>>
>> #include <linux/devfreq.h>
>> +#include <linux/soc/qcom/llcc-qcom.h>
>>
>> #define GPU_PAS_ID 13
>>
>> @@ -781,6 +782,117 @@ static void
>> a6xx_bus_clear_pending_transactions(struct adreno_gpu *adreno_gpu)
>> gpu_write(gpu, REG_A6XX_GBIF_HALT, 0x0);
>> }
>>
>> +#define A6XX_LLC_NUM_GPU_SCIDS 5
>> +#define A6XX_GPU_LLC_SCID_NUM_BITS 5
>
> As I mention below, I'm not sure if we need these
>
>> +#define A6XX_GPU_LLC_SCID_MASK \
>> + ((1 << (A6XX_LLC_NUM_GPU_SCIDS * A6XX_GPU_LLC_SCID_NUM_BITS)) - 1)
>> +
>> +#define A6XX_GPUHTW_LLC_SCID_SHIFT 25
>> +#define A6XX_GPUHTW_LLC_SCID_MASK \
>> + (((1 << A6XX_GPU_LLC_SCID_NUM_BITS) - 1) <<
>> A6XX_GPUHTW_LLC_SCID_SHIFT)
>> +
>
> Normally these go into the envytools regmap but if we're going to do
> these guys
> lets use the power of <linux/bitfield.h> for good.
>
> #define A6XX_GPU_LLC_SCID GENMASK(24, 0)
> #define A6XX_GPUHTW_LLC_SCID GENMASK(29, 25)
>
>> +static inline void a6xx_gpu_cx_rmw(struct a6xx_llc *llc,
>
> Don't mark C functions as inline - let the compiler figure it out for
> you.
>
>> + u32 reg, u32 mask, u32 or)
>> +{
>> + msm_rmw(llc->mmio + (reg << 2), mask, or);
>> +}
>> +
>> +static void a6xx_llc_deactivate(struct a6xx_llc *llc)
>> +{
>> + llcc_slice_deactivate(llc->gpu_llc_slice);
>> + llcc_slice_deactivate(llc->gpuhtw_llc_slice);
>> +}
>> +
>> +static void a6xx_llc_activate(struct a6xx_llc *llc)
>> +{
>> + if (!llc->mmio)
>> + return;
>> +
>> + /* Program the sub-cache ID for all GPU blocks */
>> + if (!llcc_slice_activate(llc->gpu_llc_slice))
>> + a6xx_gpu_cx_rmw(llc,
>> + REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_1,
>> + A6XX_GPU_LLC_SCID_MASK,
>> + (llc->cntl1_regval &
>> + A6XX_GPU_LLC_SCID_MASK));
>
> This is out of order with the comments below, but if we store the slice
> id then
> you could calculate regval here and not have to store it.
>
>> +
>> + /* Program the sub-cache ID for the GPU pagetables */
>> + if (!llcc_slice_activate(llc->gpuhtw_llc_slice))
>
> val |= FIELD_SET(A6XX_GPUHTW_LLC_SCID, htw_llc_sliceid);
>
>> + a6xx_gpu_cx_rmw(llc,
>> + REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_1,
>> + A6XX_GPUHTW_LLC_SCID_MASK,
>> + (llc->cntl1_regval &
>> + A6XX_GPUHTW_LLC_SCID_MASK));
>
> And this could be FIELD_SET(A6XX_GPUHTW_LLC_SCID, sliceid);
>
> In theory you could just calculate the u32 and write it directly
> without a rmw.
> In fact, that might be preferable - if the slice activate failed, you
> don't want
> to run the risk that the scid for htw is still populated.
>
>> +
>> + /* Program cacheability overrides */
>> + a6xx_gpu_cx_rmw(llc, REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_0, 0xF,
>> + llc->cntl0_regval);
>
> As below, this could easily be a constant.
>
>> +}
>> +
>> +static void a6xx_llc_slices_destroy(struct a6xx_llc *llc)
>> +{
>> + if (llc->mmio)
>> + iounmap(llc->mmio);
>
> msm_ioremap returns a devm_ managed resource, so do not use iounmap()
> to free
> it. Bets to just leave it and let the gpu device handle it when it goes
> boom.
>
>> +
>> + llcc_slice_putd(llc->gpu_llc_slice);
>> + llcc_slice_putd(llc->gpuhtw_llc_slice);
>> +}
>> +
>> +static int a6xx_llc_slices_init(struct platform_device *pdev,
> T
> This can be void, I don't think we care if it passes or fails.
>
>> + struct a6xx_llc *llc)
>> +{
>> + llc->mmio = msm_ioremap(pdev, "cx_mem", "gpu_cx");
>> + if (IS_ERR_OR_NULL(llc->mmio))
>
> msm_ioremap can not return NULL.
>
>> + return -ENODEV;
>> +
>> + llc->gpu_llc_slice = llcc_slice_getd(LLCC_GPU);
>> + llc->gpuhtw_llc_slice = llcc_slice_getd(LLCC_GPUHTW);
>> + if (IS_ERR(llc->gpu_llc_slice) && IS_ERR(llc->gpuhtw_llc_slice))
>> + return -ENODEV;
>> +
>> + /*
>> + * CNTL0 provides options to override the settings for the
>> + * read and write allocation policies for the LLC. These
>> + * overrides are global for all memory transactions from
>> + * the GPU.
>> + *
>> + * 0x3: read-no-alloc-overridden = 0
>> + * read-no-alloc = 0 - Allocate lines on read miss
>> + * write-no-alloc-overridden = 1
>> + * write-no-alloc = 1 - Do not allocates lines on write miss
>> + */
>> + llc->cntl0_regval = 0x03;
>
> This is a fixed value isn't it? We should be able to get away with
> writing a
> constant.
>
>> +
>> + /*
>> + * CNTL1 is used to specify SCID for (CP, TP, VFD, CCU and UBWC
>> + * FLAG cache) GPU blocks. This value will be passed along with
>> + * the address for any memory transaction from GPU to identify
>> + * the sub-cache for that transaction.
>> + */
>> + if (!IS_ERR(llc->gpu_llc_slice)) {
>> + u32 gpu_scid = llcc_get_slice_id(llc->gpu_llc_slice);
>> + int i;
>> +
>> + for (i = 0; i < A6XX_LLC_NUM_GPU_SCIDS; i++)
>> + llc->cntl1_regval |=
>> + gpu_scid << (A6XX_GPU_LLC_SCID_NUM_BITS * i);
>
> As above, i'm not sure a loop is better than just:
>
> gpu_scid &= 0x1f;
>
> llc->cntl1_regval = (gpu_scid << 0) || (gpu_scid << 5) | (gpu_scid <<
> 10)
> | (gpu_scid << 15) | (gpu_scid << 20);
>
> And I'm not even sure we need do this math here in the first place.
>
>> + }
>> +
>> + /*
>> + * Set SCID for GPU IOMMU. This will be used to access
>> + * page tables that are cached in LLC.
>> + */
>> + if (!IS_ERR(llc->gpuhtw_llc_slice)) {
>> + u32 gpuhtw_scid = llcc_get_slice_id(llc->gpuhtw_llc_slice);
>> +
>> + llc->cntl1_regval |=
>> + gpuhtw_scid << A6XX_GPUHTW_LLC_SCID_SHIFT;
>> + }
>
> As above, I think storing the slice id could be more beneficial than
> calculating
> a value, but if we do calculate a value, use
> FIELD_SET(A6XX_GPUHTW_LLC_SCID, )
>
>> +
>> + return 0;
>> +}
>> +
>> static int a6xx_pm_resume(struct msm_gpu *gpu)
>> {
>> struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>> @@ -795,6 +907,8 @@ static int a6xx_pm_resume(struct msm_gpu *gpu)
>>
>> msm_gpu_resume_devfreq(gpu);
>>
>> + a6xx_llc_activate(&a6xx_gpu->llc);
>> +
>> return 0;
>> }
>>
>> @@ -803,6 +917,8 @@ static int a6xx_pm_suspend(struct msm_gpu *gpu)
>> struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>> struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>>
>> + a6xx_llc_deactivate(&a6xx_gpu->llc);
>> +
>> devfreq_suspend_device(gpu->devfreq.devfreq);
>>
>> /*
>> @@ -851,6 +967,7 @@ static void a6xx_destroy(struct msm_gpu *gpu)
>> drm_gem_object_put_unlocked(a6xx_gpu->sqe_bo);
>> }
>>
>> + a6xx_llc_slices_destroy(&a6xx_gpu->llc);
>> a6xx_gmu_remove(a6xx_gpu);
>>
>> adreno_gpu_cleanup(adreno_gpu);
>> @@ -924,7 +1041,10 @@ struct msm_gpu *a6xx_gpu_init(struct drm_device
>> *dev)
>> adreno_gpu->registers = NULL;
>> adreno_gpu->reg_offsets = a6xx_register_offsets;
>>
>> - ret = adreno_gpu_init(dev, pdev, adreno_gpu, &funcs, 1, 0);
>> + ret = a6xx_llc_slices_init(pdev, &a6xx_gpu->llc);
>> +
>
> Confirming we don't care if a6xx_llc_slices_init passes or fails.

Are you suggesting to unconditionally set the memory attributes in
iommu(see the code below in msm_iommu.c).
We probably wouldn't need this patch too in that case:
https://patchwork.freedesktop.org/patch/346097/

The return code is used in the line below to pass
MMU_FEATURE_USE_SYSTEM_CACHE. Am I missing something here?

>
>> + ret = adreno_gpu_init(dev, pdev, adreno_gpu, &funcs, 1,
>> + ret ? 0 : MMU_FEATURE_USE_SYSTEM_CACHE);
>> if (ret) {
>> a6xx_destroy(&(a6xx_gpu->base.base));
>> return ERR_PTR(ret);
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>> index 7239b8b..09b9ad0 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
>> @@ -12,6 +12,14 @@
>>
>> extern bool hang_debug;
>>
>> +struct a6xx_llc {
>> + void __iomem *mmio;
>> + void *gpu_llc_slice;
>> + void *gpuhtw_llc_slice;
>> + u32 cntl0_regval;
>
> As above, I'm not sure if cntl0 is needed. Heck, I'm not even sure
> cntl1 is
> needed - since we could store or query the ids at activate time.
>
>> + u32 cntl1_regval;
>> +};
>> +
>> struct a6xx_gpu {
>> struct adreno_gpu base;
>>
>> @@ -21,6 +29,7 @@ struct a6xx_gpu {
>> struct msm_ringbuffer *cur_ring;
>>
>> struct a6xx_gmu gmu;
>> + struct a6xx_llc llc;
>> };
>>
>> #define to_a6xx_gpu(x) container_of(x, struct a6xx_gpu, base)
>> diff --git a/drivers/gpu/drm/msm/msm_iommu.c
>> b/drivers/gpu/drm/msm/msm_iommu.c
>> index 8c95c31..4699367 100644
>> --- a/drivers/gpu/drm/msm/msm_iommu.c
>> +++ b/drivers/gpu/drm/msm/msm_iommu.c
>> @@ -27,6 +27,16 @@ static int msm_iommu_attach(struct msm_mmu *mmu,
>> const char * const *names,
>> int cnt)
>> {
>> struct msm_iommu *iommu = to_msm_iommu(mmu);
>> + int gpu_htw_llc = 1;
>> +
>> + /*
>> + * This allows GPU to set the bus attributes required
>> + * to use system cache on behalf of the iommu page table
>> + * walker.
>> + */
>> + if (msm_mmu_has_feature(mmu, MMU_FEATURE_USE_SYSTEM_CACHE))
>> + iommu_domain_set_attr(iommu->domain,
>> + DOMAIN_ATTR_QCOM_SYS_CACHE, &gpu_htw_llc);
>
> We're all okay if this fails? No harm no foul?
>
>>
>> return iommu_attach_device(iommu->domain, mmu->dev);
>> }
>> @@ -45,6 +55,9 @@ static int msm_iommu_map(struct msm_mmu *mmu,
>> uint64_t iova,
>> struct msm_iommu *iommu = to_msm_iommu(mmu);
>> size_t ret;
>>
>> + if (msm_mmu_has_feature(mmu, MMU_FEATURE_USE_SYSTEM_CACHE))
>> + prot |= IOMMU_QCOM_SYS_CACHE;
>> +
>> ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);
>> WARN_ON(!ret);
>>
>> diff --git a/drivers/gpu/drm/msm/msm_mmu.h
>> b/drivers/gpu/drm/msm/msm_mmu.h
>> index 1e4ac36d..3e6bdad 100644
>> --- a/drivers/gpu/drm/msm/msm_mmu.h
>> +++ b/drivers/gpu/drm/msm/msm_mmu.h
>> @@ -18,6 +18,9 @@ struct msm_mmu_funcs {
>> void (*destroy)(struct msm_mmu *mmu);
>> };
>>
>> +/* MMU features */
>> +#define MMU_FEATURE_USE_SYSTEM_CACHE (1 << 0)
>> +
>> struct msm_mmu {
>> const struct msm_mmu_funcs *funcs;
>> struct device *dev;
>> --
>> 1.9.1
>>

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