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

["mirela.rabulea@oss.nxp.com" <mirela.rabulea@oss.nxp.com>]

On 06.06.2022 05:33, Ming Qian wrote:
>> From: Mirela Rabulea (OSS) <mirela.rabulea@oss.nxp.com>
>> Sent: 2022年6月6日 0:43
>> To: Ming Qian <ming.qian@nxp.com>; mchehab@kernel.org;
>> hverkuil-cisco@xs4all.nl
>> Cc: shawnguo@kernel.org; s.hauer@pengutronix.de; kernel@pengutronix.de;
>> festevam@gmail.com; dl-linux-imx <linux-imx@nxp.com>;
>> linux-media@vger.kernel.org; linux-kernel@vger.kernel.org;
>> devicetree@vger.kernel.org; linux-arm-kernel@lists.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@nxp.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));
>>
> 
> Hi Mirela,
> 
> Yes, I think it should work if we disable slot interrupt when frame done.
> And which solution do you prefer?

Hi Ming, I don't have a strong preference, but just in case we decide to 
later use some of these interrupts, I would suggest to go with the 
disabling after FRMDONE.

Please do not forget to clean the other code related to "Instance 
released before the end of transaction".

Thanks,
Mirela

> 
> Ming
> 
>> 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)