Re: [PATCH v2 4/9] drm/panthor: Implement optional reset

[Marek Vasut <marek.vasut@mailbox.org>]

On 9/4/25 4:39 PM, Alexander Stein wrote:
> Hi,
> 
> Am Donnerstag, 4. September 2025, 15:52:38 CEST schrieb Marek Vasut:
>> On 9/4/25 8:36 AM, Alexander Stein wrote:
>>
>> Hello Alexander,
>>
>>>>> Maybe the GPU remains halted because
>>>>> setting the GLB_HALT stops command stream processing, and the GPU never
>>>>> samples the clearing of GLB_HALT and therefore remains halted forever ?
>>>>
>>>> Exactly that, and that's expected.
>>>
>>> FYI: in a new release of system manager software (starting from lf-6.12.3-1.0.0),
>>> the GPU reset is reasserted in SM software already [1] and access to GPU
>>> block control has been removed from Cortex-A [2]. Starting from B0 step this
>>> version is required AFAIK.
>>
>> I don't think the SM is involved in this, because if I do the following
>> test, the MCU also fails to boot unless I do a reset:
> 
> Is this some other reset than BLK_CTRL_GPUMIX? If so, it might be required.
> Don't know much about internal details though.
Yes

    296	/**
    297	 * panthor_gpu_soft_reset() - Issue a soft-reset
    298	 * @ptdev: Device.
    299	 *
    300	 * Return: 0 on success, a negative error code otherwise.
    301	 */
    302	int panthor_gpu_soft_reset(struct panthor_device *ptdev)
    303	{
    304		bool timedout = false;
    305		unsigned long flags;
    306	
    307		spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
    308		if (!drm_WARN_ON(&ptdev->base,
    309				 ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED)) {
    310			ptdev->gpu->pending_reqs |= GPU_IRQ_RESET_COMPLETED;
    311			gpu_write(ptdev, GPU_INT_CLEAR, GPU_IRQ_RESET_COMPLETED);
    312			gpu_write(ptdev, GPU_CMD, GPU_SOFT_RESET);
    313		}
    314		spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
    315	
    316		if (!wait_event_timeout(ptdev->gpu->reqs_acked,
    317					!(ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED),
    318					msecs_to_jiffies(100))) {
    319			spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
    320			if ((ptdev->gpu->pending_reqs & GPU_IRQ_RESET_COMPLETED) != 0 &&
    321			    !(gpu_read(ptdev, GPU_INT_RAWSTAT) & GPU_IRQ_RESET_COMPLETED))
    322				timedout = true;
    323			else
    324				ptdev->gpu->pending_reqs &= ~GPU_IRQ_RESET_COMPLETED;
    325			spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
    326		}
    327	
    328		if (timedout) {
    329			drm_err(&ptdev->base, "Soft reset timeout");
    330			return -ETIMEDOUT;
    331		}
    332	
    333		return 0;
    334	}