Re: [PATCHv5 4/6] drm/msm/a6xx: Add support for using system cache(LLC)

Sai Prakash Ranjan
2020-09-28T16:30:23Z

On 2020-09-28 21:41, Jordan Crouse wrote:
> On Mon, Sep 28, 2020 at 05:56:55PM +0530, Sai Prakash Ranjan wrote:
>> Hi Jordan,
>>
>> On 2020-09-23 20:33, Jordan Crouse wrote:
>> >On Tue, Sep 22, 2020 at 11:48:17AM +0530, Sai Prakash Ranjan wrote:
>> >>From: Sharat Masetty <smasetty@codeaurora.org>
>> >>
>> >>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 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 to set the right TCR attributes. 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.
>> >>
>> >>DOMAIN_ATTR_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>
>> >>[saiprakash.ranjan: fix to set attr before device attach to iommu and
>> >>rebase]
>> >>Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> >>---
>> >> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 83 +++++++++++++++++++++++++
>> >> drivers/gpu/drm/msm/adreno/a6xx_gpu.h | 4 ++
>> >> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 17 +++++
>> >> 3 files changed, 104 insertions(+)
>> >>
>> >>diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> >>b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> >>index 8915882e4444..151190ff62f7 100644
>> >>--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> >>+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> >>@@ -8,7 +8,9 @@
>> >> #include "a6xx_gpu.h"
>> >> #include "a6xx_gmu.xml.h"
>> >>
>> >>+#include <linux/bitfield.h>
>> >> #include <linux/devfreq.h>
>> >>+#include <linux/soc/qcom/llcc-qcom.h>
>> >>
>> >> #define GPU_PAS_ID 13
>> >>
>> >>@@ -1022,6 +1024,79 @@ static irqreturn_t a6xx_irq(struct msm_gpu *gpu)
>> >> return IRQ_HANDLED;
>> >> }
>> >>
>> >>+static void a6xx_llc_rmw(struct a6xx_gpu *a6xx_gpu, u32 reg, u32 mask,
>> >>u32 or)
>> >>+{
>> >>+ return msm_rmw(a6xx_gpu->llc_mmio + (reg << 2), mask, or);
>> >>+}
>> >>+
>> >>+static void a6xx_llc_write(struct a6xx_gpu *a6xx_gpu, u32 reg, u32
>> >>value)
>> >>+{
>> >>+ return msm_writel(value, a6xx_gpu->llc_mmio + (reg << 2));
>> >>+}
>> >>+
>> >>+static void a6xx_llc_deactivate(struct a6xx_gpu *a6xx_gpu)
>> >>+{
>> >>+ llcc_slice_deactivate(a6xx_gpu->llc_slice);
>> >>+ llcc_slice_deactivate(a6xx_gpu->htw_llc_slice);
>> >>+}
>> >>+
>> >>+static void a6xx_llc_activate(struct a6xx_gpu *a6xx_gpu)
>> >>+{
>> >>+ u32 cntl1_regval = 0;
>> >>+
>> >>+ if (IS_ERR(a6xx_gpu->llc_mmio))
>> >>+ return;
>> >>+
>> >>+ if (!llcc_slice_activate(a6xx_gpu->llc_slice)) {
>> >>+ u32 gpu_scid = llcc_get_slice_id(a6xx_gpu->llc_slice);
>> >>+
>> >>+ gpu_scid &= 0x1f;
>> >>+ cntl1_regval = (gpu_scid << 0) | (gpu_scid << 5) | (gpu_scid << 10) |
>> >>+ (gpu_scid << 15) | (gpu_scid << 20);
>> >>+ }
>> >>+
>> >>+ if (!llcc_slice_activate(a6xx_gpu->htw_llc_slice)) {
>> >>+ u32 gpuhtw_scid = llcc_get_slice_id(a6xx_gpu->htw_llc_slice);
>> >>+
>> >>+ gpuhtw_scid &= 0x1f;
>> >>+ cntl1_regval |= FIELD_PREP(GENMASK(29, 25), gpuhtw_scid);
>> >>+ }
>> >>+
>> >>+ if (cntl1_regval) {
>> >>+ /*
>> >>+ * Program the slice IDs for the various GPU blocks and GPU MMU
>> >>+ * pagetables
>> >>+ */
>> >>+ a6xx_llc_write(a6xx_gpu, REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_1,
>> >>cntl1_regval);
>> >>+
>> >>+ /*
>> >>+ * Program cacheability overrides to not allocate cache lines on
>> >>+ * a write miss
>> >>+ */
>> >>+ a6xx_llc_rmw(a6xx_gpu, REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_0, 0xF,
>> >>0x03);
>> >>+ }
>> >>+}
>> >
>> >This code has been around long enough that it pre-dates a650. On a650 and
>> >other
>> >MMU-500 targets the htw_llc is configured by the firmware and the
>> >llc_slice is
>> >configured in a different register.
>> >
>> >I don't think we need to pause everything and add support for the MMU-500
>> >path,
>> >but we do need a way to disallow LLCC on affected targets until such time
>> >that
>> >we can get it fixed up.
>> >
>>
>> Thanks for taking a close look, does something like below look ok or
>> something
>> else is needed here?
>>
>> + /* Till the time we get in LLCC support for A650 */
>> + if (!(info && info->revn == 650))
>> + a6xx_llc_slices_init(pdev, a6xx_gpu);
>
> It doesn't look like Rob picked this up for 5.10, so we have some time
> to do it
> right. Would you like me to give you an add-on patch for mmu-500
> targets?
>

Yes that will be great.

Thanks,
Sai

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