linux-kernel - Re: [PATCH v2] media: imx-jpeg: Disable some unused interrupt

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Message-ID: <69817804-a618-32ba-06ca-3ec38ff1f124@oss.nxp.com>
Date:   Sun, 5 Jun 2022 19:42:48 +0300
From:   "mirela.rabulea@....nxp.com" <mirela.rabulea@....nxp.com>
To:     Ming Qian <ming.qian@....com>, mchehab@...nel.org,
        hverkuil-cisco@...all.nl
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] media: imx-jpeg: Disable some unused interrupt

Hi Ming,

On 30.05.2022 10:47, Ming Qian wrote:
> The interrupt STMBUF_HALF may be triggered after frame done.
> It may led to system hang if driver try to access the register after
> power off.
> And interrupt STMBUF_HALF and STMBUF_RTND have no other effect.
> So disable them and the unused interrupts.
> 
> Fixes: 2db16c6ed72ce ("media: imx-jpeg: Add V4L2 driver for i.MX8 JPEG Encoder/Decoder")
> Signed-off-by: Ming Qian <ming.qian@....com>
> ---
> v2
> - add Fixes tag
>   drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.c b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.c
> index c482228262a3..258fbee7ab66 100644
> --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.c
> +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg-hw.c
> @@ -76,7 +76,7 @@ void print_wrapper_info(struct device *dev, void __iomem *reg)
>   
>   void mxc_jpeg_enable_irq(void __iomem *reg, int slot)
>   {
> -	writel(0xFFFFFFFF, reg + MXC_SLOT_OFFSET(slot, SLOT_IRQ_EN));
> +	writel(0xF0C, reg + MXC_SLOT_OFFSET(slot, SLOT_IRQ_EN));

There is another way, less aggressive, to go around this, disable all 
the interrupts once FRMDONE is received (or some other error condition), 
interrupts will get re-enabled at the next device_run. I checked this 
works, in mxc_jpeg_dec_irq:
buffers_done:
	writel(0x0, reg + MXC_SLOT_OFFSET(slot, SLOT_IRQ_EN));

Either way, I would also replace this:
	if (!ctx) {
		dev_err(dev,
			"Instance released before the end of transaction.\n");
		/* soft reset only resets internal state, not registers */
		mxc_jpeg_sw_reset(reg);
		/* clear all interrupts */
		writel(0xFFFFFFFF, reg + MXC_SLOT_OFFSET(slot, SLOT_STATUS));
		goto job_unlock;
	}

With something like:
BUG_ON(!ctx)

The initial intent of this code was to cope with the same problem, 
STMBUF_HALF interrupt received after FRMDONE, which could not be 
cleared, but it was not done right, I can see the hang in some rare 
cases. We should not run into it anymore, with interrupts disabled, 
either the way you proposed, or mine.

Regards,
Mirela

>   }
>   
>   void mxc_jpeg_sw_reset(void __iomem *reg)