linux-kernel - Re: [PATCH] media: aspeed: use reset to replace clk off/on

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Message-ID: <398d37a5-509f-b78b-360b-990d256bde63@xs4all.nl>
Date:   Mon, 8 Nov 2021 09:53:23 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Jammy Huang <jammy_huang@...eedtech.com>,
        Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>,
        "eajames@...ux.ibm.com" <eajames@...ux.ibm.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "joel@....id.au" <joel@....id.au>,
        "andrew@...id.au" <andrew@...id.au>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: aspeed: use reset to replace clk off/on

Hi Jammy,

On 05/11/2021 02:27, Jammy Huang wrote:
> Hi Jae,
> 
> OK, I found it.
> Thanks for your help.

So just so I understand this correctly: this patch can be dropped, right?

Regards,

	Hans

> 
> Regards,
> Jammy Huang
> 
> Tel: 886-3-575-1185  ext.8630
> 
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> 
> -----Original Message-----
> From: Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com> 
> Sent: Thursday, November 4, 2021 11:54 PM
> To: Jammy Huang <jammy_huang@...eedtech.com>; eajames@...ux.ibm.com; mchehab@...nel.org; joel@....id.au; andrew@...id.au; linux-media@...r.kernel.org; openbmc@...ts.ozlabs.org; linux-arm-kernel@...ts.infradead.org; linux-aspeed@...ts.ozlabs.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] media: aspeed: use reset to replace clk off/on
> 
> Hi Jammy,
> 
> On 11/2/2021 10:43 PM, Jammy Huang wrote:
>> reset should be more proper than clk off/on to bring HW back to good 
>> state.
>>
>> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
>> ---
>>   drivers/media/platform/aspeed-video.c | 22 +++++++++++++++++++---
>>   1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/media/platform/aspeed-video.c 
>> b/drivers/media/platform/aspeed-video.c
>> index fea5e4d0927e..10d182139809 100644
>> --- a/drivers/media/platform/aspeed-video.c
>> +++ b/drivers/media/platform/aspeed-video.c
>> @@ -23,6 +23,7 @@
>>   #include <linux/workqueue.h>
>>   #include <linux/debugfs.h>
>>   #include <linux/ktime.h>
>> +#include <linux/reset.h>
>>   #include <media/v4l2-ctrls.h>
>>   #include <media/v4l2-dev.h>
>>   #include <media/v4l2-device.h>
>> @@ -220,6 +221,7 @@ struct aspeed_video {
>>   	void __iomem *base;
>>   	struct clk *eclk;
>>   	struct clk *vclk;
>> +	struct reset_control *reset;
>>   
>>   	struct device *dev;
>>   	struct v4l2_ctrl_handler ctrl_handler; @@ -554,6 +556,13 @@ static 
>> void aspeed_video_on(struct aspeed_video *video)
>>   	set_bit(VIDEO_CLOCKS_ON, &video->flags);
>>   }
>>   
>> +static void aspeed_video_reset(struct aspeed_video *v) {
>> +	reset_control_assert(v->reset);
>> +	udelay(100);
>> +	reset_control_deassert(v->reset);
>> +}
>> +
>>   static void aspeed_video_bufs_done(struct aspeed_video *video,
>>   				   enum vb2_buffer_state state)
>>   {
>> @@ -574,7 +583,9 @@ static void aspeed_video_irq_res_change(struct aspeed_video *video, ulong delay)
>>   	set_bit(VIDEO_RES_CHANGE, &video->flags);
>>   	clear_bit(VIDEO_FRAME_INPRG, &video->flags);
>>   
>> -	aspeed_video_off(video);
>> +	aspeed_video_write(video, VE_INTERRUPT_CTRL, 0);
>> +	aspeed_video_write(video, VE_INTERRUPT_STATUS, 0xffffffff);
>> +	aspeed_video_reset(video);
>>   	aspeed_video_bufs_done(video, VB2_BUF_STATE_ERROR);
>>   
>>   	schedule_delayed_work(&video->res_work, delay); @@ -1507,8 +1518,7 
>> @@ static void aspeed_video_stop_streaming(struct vb2_queue *q)
>>   		 * Need to force stop any DMA and try and get HW into a good
>>   		 * state for future calls to start streaming again.
>>   		 */
>> -		aspeed_video_off(video);
>> -		aspeed_video_on(video);
>> +		aspeed_video_reset(video);
> 
> You can find the ECLK configuration in 'clk-aspeed.c' or in 'clk-ast2600.c' that it's coupled with the video engine reset (SCU04[6] for AST2500 / SCU040[6] for AST2600). It means that if we call
> clk_disable() and clk_enable() through aspeed_video_off() and aspeed_video_on(), the video engine reset will be implicitly asserted and de-asserted by the clock driver so the reset mechanism is already in the existing code.
> 
> Thanks,
> Jae
> 
>>   		aspeed_video_init_regs(video);
>>   
>> @@ -1715,6 +1725,12 @@ static int aspeed_video_init(struct aspeed_video *video)
>>   		return rc;
>>   	}
>>   
>> +	video->reset = devm_reset_control_get(dev, NULL);
>> +	if (IS_ERR(video->reset)) {
>> +		dev_err(dev, "Unable to get reset\n");
>> +		return PTR_ERR(video->reset);
>> +	}
>> +
>>   	video->eclk = devm_clk_get(dev, "eclk");
>>   	if (IS_ERR(video->eclk)) {
>>   		dev_err(dev, "Unable to get ECLK\n");
>>