linux-kernel - Re: [PATCH v1 2/5] media: chips-media: wave5: Avoid race condition for interrupt handling

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Message-ID: <9b7be78c58d0bd157541a6c4db0d742e3f9bab58.camel@collabora.com>
Date: Fri, 13 Dec 2024 14:36:15 -0500
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: "Jackson.lee" <jackson.lee@...psnmedia.com>, mchehab@...nel.org, 
	hverkuil-cisco@...all.nl, sebastian.fricke@...labora.com, 
	bob.beckett@...labora.com, dafna.hirschfeld@...labora.com
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	lafley.kim@...psnmedia.com, b-brnich@...com, hverkuil@...all.nl, 
	nas.chung@...psnmedia.com
Subject: Re: [PATCH v1 2/5] media: chips-media: wave5: Avoid race condition
 for interrupt handling

Le lundi 09 décembre 2024 à 14:36 +0900, Jackson.lee a écrit :
> In case of multi instance, interrupts can occurr for other instances as
> soon as interrupt is cleared. If driver reads the instance_info after
> clearing the interrupt, it is not guaranteed that the instance_info is
> valid for the current interrupt.
> 
> Read the instance_info register for each interrupt before clearing the
> interrupt.
> 
> Signed-off-by: Jackson.lee <jackson.lee@...psnmedia.com>
> Signed-off-by: Nas Chung <nas.chung@...psnmedia.com>
> ---
>  drivers/media/platform/chips-media/wave5/wave5-vpu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpu.c b/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> index 6b294a2d6717..63a607d10433 100644
> --- a/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> @@ -55,12 +55,12 @@ static void wave5_vpu_handle_irq(void *dev_id)
>  	struct vpu_device *dev = dev_id;
>  
>  	irq_reason = wave5_vdi_read_register(dev, W5_VPU_VINT_REASON);
> +	seq_done = wave5_vdi_read_register(dev, W5_RET_SEQ_DONE_INSTANCE_INFO);
> +	cmd_done = wave5_vdi_read_register(dev, W5_RET_QUEUE_CMD_DONE_INST);
>  	wave5_vdi_write_register(dev, W5_VPU_VINT_REASON_CLR, irq_reason);
>  	wave5_vdi_write_register(dev, W5_VPU_VINT_CLEAR, 0x1);
>  
>  	list_for_each_entry(inst, &dev->instances, list) {
> -		seq_done = wave5_vdi_read_register(dev, W5_RET_SEQ_DONE_INSTANCE_INFO);
> -		cmd_done = wave5_vdi_read_register(dev, W5_RET_QUEUE_CMD_DONE_INST);

Right, and was a bit silly to read the register N-times, good catch.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>

>  
>  		if (irq_reason & BIT(INT_WAVE5_INIT_SEQ) ||
>  		    irq_reason & BIT(INT_WAVE5_ENC_SET_PARAM)) {