Re: [PATCH v1 4/6] drm/panfrost: Add support for AARCH64_4K page table format
From: Ariel D'Alessandro
Date: Wed Mar 12 2025 - 13:49:46 EST
Boris,
On 3/11/25 5:05 AM, Boris Brezillon wrote:
On Mon, 10 Mar 2025 16:59:19 -0300
Ariel D'Alessandro <ariel.dalessandro@xxxxxxxxxxxxx> wrote:
Currently, Panfrost only supports MMU configuration in "LEGACY" (as
Bifrost calls it) mode, a (modified) version of LPAE "Large Physical
Address Extension", which in Linux we've called "mali_lpae".
This commit adds support for conditionally enabling AARCH64_4K page
table format. To achieve that, a "GPU optional configurations" field was
added to `struct panfrost_features` with the related flag.
Note that, in order to enable AARCH64_4K mode, the GPU variant must have
the HW_FEATURE_AARCH64_MMU feature flag present.
Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@xxxxxxxxxxxxx>
---
drivers/gpu/drm/panfrost/panfrost_device.h | 16 +++
drivers/gpu/drm/panfrost/panfrost_mmu.c | 132 +++++++++++++++++++--
drivers/gpu/drm/panfrost/panfrost_regs.h | 34 ++++++
3 files changed, 169 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
index cffcb0ac7c111..0385702aa43c7 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.h
+++ b/drivers/gpu/drm/panfrost/panfrost_device.h
@@ -42,6 +42,14 @@ enum panfrost_gpu_pm {
GPU_PM_VREG_OFF,
};
+/**
+ * enum panfrost_gpu_config - GPU optional configurations
+ * @GPU_CONFIG_AARCH64_4K: Use AARCH64_4K page table format
+ */
+enum panfrost_gpu_config {
+ GPU_CONFIG_AARCH64_4K,
+};
+
struct panfrost_features {
u16 id;
u16 revision;
@@ -95,6 +103,9 @@ struct panfrost_compatible {
/* Allowed PM features */
u8 pm_features;
+
+ /* GPU features */
+ u8 gpu_configs;
I would probably name this gpu_quirks, with the GPU_CONFIG_AARCH64_4K
flag renamed GPU_QUIRK_FORCE_AARCH64_PAGE_TABLE.
Will follow on this thread after latest responses.
};
struct panfrost_device {
@@ -162,6 +173,11 @@ struct panfrost_mmu {
int as;
atomic_t as_count;
struct list_head list;
+ struct {
+ u64 transtab;
+ u64 memattr;
+ u64 transcfg;
+ } cfg;
};
struct panfrost_engine_usage {
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index 31df3a96f89bd..4a9b8de2ff987 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -26,6 +26,48 @@
[snip]
+static void mmu_cfg_init_aarch64_4k(struct panfrost_mmu *mmu)
+{
+ struct io_pgtable_cfg *pgtbl_cfg = &mmu->pgtbl_cfg;
+
+ mmu->cfg.transtab = pgtbl_cfg->arm_lpae_s1_cfg.ttbr &
+ AS_TRANSTAB_AARCH64_4K_ADDR_MASK;
Silently masking the low 4bits is not the solution, it's just papering
over a real issue. If pgtbl_cfg->arm_lpae_s1_cfg.ttbr is not aligned on
16 bytes (PAGE_SIZE even) we have a problem, so I would drm_WARN_ON()
here, and return an error so we can fail the probe.
Good point. I'll add something like this in v2:
if (drm_WARN_ON(pfdev->ddev, pgtbl_cfg->arm_lpae_s1_cfg.ttbr &
~AS_TRANSTAB_AARCH64_4K_ADDR_MASK))
return -EINVAL;
+
+ mmu->cfg.memattr = mair_to_memattr(pgtbl_cfg->arm_lpae_s1_cfg.mair,
+ pgtbl_cfg->coherent_walk);
+
+ mmu->cfg.transcfg = AS_TRANSCFG_PTW_MEMATTR_WB |
+ AS_TRANSCFG_PTW_RA |
+ AS_TRANSCFG_ADRMODE_AARCH64_4K |
+ AS_TRANSCFG_INA_BITS(55 - pgtbl_cfg->ias);
+ if (pgtbl_cfg->coherent_walk)
+ mmu->cfg.transcfg |= AS_TRANSCFG_PTW_SH_OS;
+}
[snip]
@@ -616,6 +709,7 @@ struct panfrost_mmu *panfrost_mmu_ctx_create(struct panfrost_device *pfdev)
{
u32 va_bits = GPU_MMU_FEATURES_VA_BITS(pfdev->features.mmu_features);
u32 pa_bits = GPU_MMU_FEATURES_PA_BITS(pfdev->features.mmu_features);
+ enum io_pgtable_fmt fmt = ARM_MALI_LPAE;
struct panfrost_mmu *mmu;
mmu = kzalloc(sizeof(*mmu), GFP_KERNEL);
@@ -641,16 +735,28 @@ struct panfrost_mmu *panfrost_mmu_ctx_create(struct panfrost_device *pfdev)
.iommu_dev = pfdev->dev,
};
- mmu->pgtbl_ops = alloc_io_pgtable_ops(ARM_MALI_LPAE, &mmu->pgtbl_cfg,
- mmu);
- if (!mmu->pgtbl_ops) {
- kfree(mmu);
- return ERR_PTR(-EINVAL);
+ if (pfdev->comp->gpu_configs & BIT(GPU_CONFIG_AARCH64_4K)) {
+ if (!panfrost_has_hw_feature(pfdev, HW_FEATURE_AARCH64_MMU)) {
+ dev_err_once(pfdev->dev,
+ "AARCH64_4K page table not supported\n");
+ goto err_free_mmu;
+ }
+ fmt = ARM_64_LPAE_S1;
}
How about moving this check before allocating the mmu object, so you
don't have to free it if it fails?
Yes, will fix in v2.
Thanks!
--
Ariel D'Alessandro
Software Engineer
Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718