[PATCH v6 5/5] drm/v3d: Use V3D_SMS registers for power on/off and reset on V3D 7.x

[Stefan Wahren]

Am 27.03.25 um 14:52 schrieb Maíra Canal:
> Hi Stefan,
>
> On 27/03/25 07:57, Stefan Wahren wrote:
>> Hi Maíra,
>>
>> Am 18.03.25 um 02:01 schrieb Maíra Canal:
>>> In addition to the standard reset controller, V3D 7.x requires
>>> configuring
>>> the V3D_SMS registers for proper power on/off and reset. Add the new
>>> registers to `v3d_regs.h` and ensure they are properly configured
>>> during
>>> device probing, removal, and reset.
>>>
>>> This change fixes GPU reset issues on the Raspberry Pi 5 (BCM2712).
>>> Without exposing these registers, a GPU reset causes the GPU to hang,
>>> stopping any further job execution and freezing the desktop GUI. The
>>> same
>>> issue occurs when unloading and loading the v3d driver.
>>>
>>> Link: https://github.com/raspberrypi/linux/issues/6660
>>> Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>
>>> Signed-off-by: Maíra Canal <mcanal at igalia.com>
>>> ---
>>>   drivers/gpu/drm/v3d/v3d_drv.c  | 40
>>> ++++++++++++++++++++++++++++++++ ++++++++
>>>   drivers/gpu/drm/v3d/v3d_drv.h  | 11 +++++++++++
>>>   drivers/gpu/drm/v3d/v3d_gem.c  | 17 +++++++++++++++++
>>>   drivers/gpu/drm/v3d/v3d_regs.h | 26 ++++++++++++++++++++++++++
>>>   4 files changed, 94 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/
>>> v3d_drv.c
>>> index
>>> c63f0ed1bd8a3d5511085e76ed2fbd6ee7df6f80..122848cdccc4a02039d9ea2e77aa2f377886b5d6
>>> 100644
>>> --- a/drivers/gpu/drm/v3d/v3d_drv.c
>>> +++ b/drivers/gpu/drm/v3d/v3d_drv.c
>>> @@ -263,6 +263,36 @@ static const struct of_device_id v3d_of_match[]
>>> = {
>>>   };
>>>   MODULE_DEVICE_TABLE(of, v3d_of_match);
>>>
>>> +static void
>>> +v3d_idle_sms(struct v3d_dev *v3d)
>>> +{
>>> +    if (v3d->ver < V3D_GEN_71)
>>> +        return;
>>> +
>>> +    V3D_SMS_WRITE(V3D_SMS_TEE_CS, V3D_SMS_CLEAR_POWER_OFF);
>>> +
>>> +    if (wait_for((V3D_GET_FIELD(V3D_SMS_READ(V3D_SMS_TEE_CS),
>>> +                    V3D_SMS_STATE) == V3D_SMS_IDLE), 100)) {
>>> +        DRM_ERROR("Failed to power up SMS\n");
>>> +    }
>>> +
>>> +    v3d_reset_sms(v3d);
>>> +}
>>> +
>>> +static void
>>> +v3d_power_off_sms(struct v3d_dev *v3d)
>>> +{
>>> +    if (v3d->ver < V3D_GEN_71)
>>> +        return;
>>> +
>>> +    V3D_SMS_WRITE(V3D_SMS_TEE_CS, V3D_SMS_POWER_OFF);
>>> +
>>> +    if (wait_for((V3D_GET_FIELD(V3D_SMS_READ(V3D_SMS_TEE_CS),
>>> +                    V3D_SMS_STATE) == V3D_SMS_POWER_OFF_STATE),
>>> 100)) {
>>> +        DRM_ERROR("Failed to power off SMS\n");
>>> +    }
>>> +}
>>> +
>>>   static int
>>>   map_regs(struct v3d_dev *v3d, void __iomem **regs, const char *name)
>>>   {
>>> @@ -300,6 +330,12 @@ static int v3d_platform_drm_probe(struct
>>> platform_device *pdev)
>>>       if (ret)
>>>           return ret;
>>>
>>> +    if (v3d->ver >= V3D_GEN_71) {
>>> +        ret = map_regs(v3d, &v3d->sms_regs, "sms");
>>> +        if (ret)
>>> +            return ret;
>> Is it correct, that BCM2712 now requires the SMS register and otherwise
>> the driver doesn't probe?
>
> Hum, yeah, it is correct, but I can send a patch to ensure backwards
> compatibility. But keep in mind that you won't be able to reset the GPU
> or unload/load (power on/off).
>
>>
>> Just a note for the future: the devicetree is considered as an ABI [1],
>> so new kernels should still work with old DTB (no regression). For
>> Raspberry Pi OS, the kernel and DTB are always updated, but this doesn't
>> apply for Linux Mainline. AFAIK V3D doesn't work with Linux Mainline on
>> Raspberry Pi 5 yet, so this is just a theoretical problem.
>
> Yeah, I had that in mind, but due to the reason pointed in the end of
> your comment, it was okay to do so and ensure that reset and power on/
> off will work when RPi 5 reach upstream support.
Fine :-)
>
> But, I'm open to send a patch removing the requirement.
I think, this is not necessary. There is no need to introduce such
"complexity".
>
> Best Regards,
> - Maíra
>
>>
>> Best regards
>>
>> [1] - https://docs.kernel.org/devicetree/bindings/ABI.html
>