Dear Hans,

On 2021/11/8 ?? 04:53, Hans Verkuil wrote:

Hi Jammy,

On 05/11/2021 02:27, Jammy Huang wrote:

quoted

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

Yes, aspeed clk driver will reset the related engine at clk-enabled.

Thus, this modification isn't necessary.

quoted

Regards,
Jammy Huang

Tel: 886-3-575-1185? ext.8630

************* Email Confidentiality Notice ********************
DISCLAIMER:
This message (and any attachments) may contain legally privileged and/or other confidential information. If you have received it in error, please notify the sender by reply e-mail and immediately delete the e-mail and any attachments without copying or disclosing the contents. Thank you.

-----Original Message-----
From: Jae Hyun Yoo <redacted>
Sent: Thursday, November 4, 2021 11:54 PM
To: Jammy Huang <redacted>; eajames at linux.ibm.com; mchehab at kernel.org; joel at jms.id.au; andrew at aj.id.au; linux-media at vger.kernel.org; openbmc at lists.ozlabs.org; linux-arm-kernel at lists.infradead.org; linux-aspeed at lists.ozlabs.org; linux-kernel at vger.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:

quoted

reset should be more proper than clk off/on to bring HW back to good
state.

Signed-off-by: Jammy Huang <redacted>
---
   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

quoted

   		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");

-- 
Best Regards
Jammy