linux-kernel - Re: [PATCH v1 4/6] drm/panfrost: Add support for AARCH64

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Message-ID: <16f6a6e2-4dce-4af9-bc0a-61c4d6213f02@collabora.com>
Date: Tue, 11 Mar 2025 10:14:44 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Boris Brezillon <boris.brezillon@...labora.com>,
 Ariel D'Alessandro <ariel.dalessandro@...labora.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 robh@...nel.org, steven.price@....com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
 kernel@...labora.com, linux-mediatek@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, sjoerd@...labora.com
Subject: Re: [PATCH v1 4/6] drm/panfrost: Add support for AARCH64_4K page
 table format

Il 11/03/25 09:05, Boris Brezillon ha scritto:
> On Mon, 10 Mar 2025 16:59:19 -0300
> Ariel D'Alessandro <ariel.dalessandro@...labora.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 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@...labora.com>
>> ---
>>   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.
> 

Boris, at this point the quirk should be LPAE, not AARCH64_4K, because the
former is legacy...

I think that Ariel is right in this, as in, that's a capability of the GPU
MMU, so if anything I would rather rename it to gpu_capabilities, but then
that'd be confusing for other stuff - which means that gpu_configs is most
probably the least confusing and/or most appropriate name for this.

Of course, just IMO.

Cheers,
Angelo

>>   };
>>