linux-kernel - Re: [PATCH v4 7/7] drm/panthor: Add support for Mali-Gx20 and Mali-Gx25 GPUs

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Message-ID: <9f30764e-14fe-4674-bdf7-eb53097bc51e@arm.com>
Date: Mon, 21 Jul 2025 12:44:48 +0100
From: Karunika Choo <karunika.choo@....com>
To: Chia-I Wu <olvaffe@...il.com>
Cc: dri-devel@...ts.freedesktop.org, nd@....com,
 Boris Brezillon <boris.brezillon@...labora.com>,
 Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/7] drm/panthor: Add support for Mali-Gx20 and
 Mali-Gx25 GPUs

On 11/06/2025 00:45, Chia-I Wu wrote:
> On Mon, Jun 2, 2025 at 7:34 AM Karunika Choo <karunika.choo@....com> wrote:
>>
>> Mali-Gx20 and Mali-Gx25 deprecates the use of FLUSH_MEM and FLUSH_PT
>> MMU_AS commands in favour of cache maintenance via
>> GPU_COMMAND's FLUSH_CACHES and FLUSH_PA_RANGE.
>>
>> They also introduce the following registers:
>> - GPU_COMMAND_ARG0~1
>> - SHADER_PWRFEATURES
>> - AMBA_FEATURES
>> - AMBA_ENABLE
>>
>> This patch enables FLUSH_CACHES for both families of GPUs via the
>> PANTHOR_HW_FEATURE_GPU_CTRL_CACHE_FLUSH bit until FLUSH_PA_RANGE support
>> is added. It also adds the aforementioned register definitions and
>> firmware binary support for arch 12.8 and 13.8.
> <snipped>
>> diff --git a/drivers/gpu/drm/panthor/panthor_regs.h b/drivers/gpu/drm/panthor/panthor_regs.h
>> index 4eaa2b612756..8e01440f8743 100644
>> --- a/drivers/gpu/drm/panthor/panthor_regs.h
>> +++ b/drivers/gpu/drm/panthor/panthor_regs.h
>> @@ -89,6 +89,8 @@
>>
>>  #define GPU_DOORBELL_FEATURES                          0xC0
>>
>> +#define GPU_COMMAND_ARG(n)                             (0xD0 + ((n) * 8))
>> +
>>  #define GPU_SHADER_PRESENT                             0x100
>>  #define GPU_TILER_PRESENT                              0x110
>>  #define GPU_L2_PRESENT                                 0x120
>> @@ -98,6 +100,8 @@
>>  #define L2_READY                                       0x160
>>
>>  #define SHADER_PWRON                                   0x180
>> +#define SHADER_PWRFEATURES                             0x188
>> +#define   SHADER_PWRFEATURES_RAY_TRACING_UNIT          BIT(0)
>>  #define TILER_PWRON                                    0x190
>>  #define L2_PWRON                                       0x1A0
>>
>> @@ -125,6 +129,13 @@
>>  #define   GPU_COHERENCY_ACE                            1
>>  #define   GPU_COHERENCY_NONE                           31
>>
>> +#define AMBA_FEATURES                                  0x300
>> +#define   AMBA_FEATURES_ACE_LITE                       BIT(0)
>> +#define   AMBA_FEATURES_ACE                            BIT(1)
>> +#define   AMBA_FEATURES_SHAREABLE_CACHE_SUPPORT                BIT(5)
>> +
>> +#define AMBA_ENABLE                                    0x304
> We still use GPU_COHERENCY_FEATURES / GPU_COHERENCY_PROTOCOL even on
> v12 and v13.  I suppose they are compatible with AMBA_FEATURES /
> AMBA_ENABLE to some degree?  We should unify them.
Hello,

Due to some changes in the fields between AMBA_ENABLE and
GPU_COHERENCY_PROTOCOL, namely SHAREABLE_CACHE_SUPPORT, which has a
value of BIT(5), the previous assumption that FEATURE = BIT(PROTOCOL)
for GPU_COHERENCY_FEATURES is no longer valid.

As such, I have updated the field Macros for GPU_COHERENCY_FEATURES to
enable merging of the two register fields. Hopefully this addresses your
comments.

Kind regards,
Karunika