Re: [PATCH v2 4/6] drm/panfrost: Add support for AARCH64_4K page table format

[Ariel D'Alessandro <ariel.dalessandro@collabora.com>]

Boris,

On 3/15/25 5:43 AM, Boris Brezillon wrote:
> On Fri, 14 Mar 2025 14:38:56 -0300
> Ariel D'Alessandro <ariel.dalessandro@collabora.com> 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 quirks" 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@collabora.com>
>> ---
>>   drivers/gpu/drm/panfrost/panfrost_device.h |  16 +++
>>   drivers/gpu/drm/panfrost/panfrost_mmu.c    | 136 +++++++++++++++++++--
>>   drivers/gpu/drm/panfrost/panfrost_regs.h   |  34 ++++++
>>   3 files changed, 177 insertions(+), 9 deletions(-)
[snip]
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> index 294f86b3c25e7..f24c23e1f67b8 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> @@ -26,6 +26,48 @@
>>   #define mmu_write(dev, reg, data) writel(data, dev->iomem + reg)
>>   #define mmu_read(dev, reg) readl(dev->iomem + reg)
>>   
[snip]
>>   u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
>>   {
>>   	int as;
>> @@ -618,6 +720,18 @@ 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);
>>   	struct panfrost_mmu *mmu;
>> +	enum io_pgtable_fmt fmt;
>> +
>> +	if (pfdev->comp->gpu_quirks & BIT(GPU_QUIRK_FORCE_AARCH64_PGTABLE)) {
>> +		if (!panfrost_has_hw_feature(pfdev, HW_FEATURE_AARCH64_MMU)) {
>> +			dev_err_once(pfdev->dev,
>> +				     "AARCH64_4K page table not supported\n");
>> +			return ERR_PTR(-EINVAL);
>> +		}
>> +		fmt = ARM_64_LPAE_S1;
>> +	} else {
>> +		fmt = ARM_MALI_LPAE;
>> +	}
>>   
>>   	mmu = kzalloc(sizeof(*mmu), GFP_KERNEL);
>>   	if (!mmu)
>> @@ -642,16 +756,20 @@ 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);
>> -	}
>> +	mmu->pgtbl_ops = alloc_io_pgtable_ops(fmt, &mmu->pgtbl_cfg, mmu);
>> +	if (!mmu->pgtbl_ops)
>> +		goto err_free_mmu;
>> +
>> +	if (panfrost_mmu_cfg_init(mmu, fmt))
>> +		goto err_free_mmu;
> 
> How about propagating the error returned by panfrost_mmu_cfg_init()
> instead of assuming it's always -EINVAL on failure? Oh, and you need to
> call free_io_pgtable_ops(), not just kfree().

Ah, totally, thanks for the heads up. Will fix in v3 right away.

-- 
Ariel D'Alessandro
Software Engineer

Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK 
Registered in England & Wales, no. 5513718