Message-ID: <aV5hbvzYxKpV5OzO@kekkonen.localdomain>
Date: Wed, 7 Jan 2026 15:36:46 +0200
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Wenmeng Liu <wenmeng.liu@....qualcomm.com>
Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wenmeng Liu <quic_wenmliu@...cinc.com>
Subject: Re: [PATCH] media: i2c: imx412: Extend the power-on waiting time

Hi Wenmeng,

On Mon, Jan 05, 2026 at 04:14:21PM +0800, Wenmeng Liu wrote:
> 
> 
> On 12/30/2025 7:33 PM, Sakari Ailus wrote:
> > Hi Wenmeng,
> > 
> > On Tue, Dec 23, 2025 at 02:19:18PM +0800, Wenmeng Liu wrote:
> > > 
> > > 
> > > On 12/22/2025 10:16 PM, Dave Stevenson wrote:
> > > > Hi Wenmeng
> > > > 
> > > > On Mon, 22 Dec 2025 at 12:20, Wenmeng Liu <wenmeng.liu@....qualcomm.com> wrote:
> > > > > 
> > > > > 
> > > > > 
> > > > > On 12/22/2025 8:11 PM, Dave Stevenson wrote:
> > > > > > Hi Wenmeng & Sakari
> > > > > > 
> > > > > > On Mon, 22 Dec 2025 at 09:35, Wenmeng Liu <wenmeng.liu@....qualcomm.com> wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > > > 
> > > > > > > > > The Arducam IMX577 module requires a longer reset time than the 1000µs
> > > > > > > > > configured in the current driver. Increase the wait time after power-on
> > > > > > > > > to ensure proper initialization.
> > > > > > > > 
> > > > > > > > Is this somehow specific to the Arducam module? If so, what's there in the
> > > > > > > > module that requires this?
> > > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > Yes, This issue occurred on the Arducam 22-pin IMX577 module.
> > > > > > > I have tried changing the sequence of regulator, reset, and clock, and
> > > > > > > found that this module must wait a sufficient amount of time after reset
> > > > > > > before registers can be written (10 ms is a safe duration). This issue
> > > > > > > did not occur when using other IMX577 modules.
> > > > > > 
> > > > > > Is it the probe that fails, or starting streaming?
> > > > > > 
> > > > > > Google has found me a datasheet for IMX577 at [1]. I'm hoping you have
> > > > > > an official datasheet, so do correct the following if that has any
> > > > > > updates.
> > > > > > Section 7-2-2 on page 30 for the startup sequence.
> > > > > > 
> > > > > > The sequence is meant to be regulators, INCK, and then XCLR. The
> > > > > > driver does XCLR before clock, so that would appear to be wrong.
> > > > > > 
> > > > > > It also states that T6 as the time from XCLR to being able to read the
> > > > > > version register is min 0.6ms, but T7 as the time before you can send
> > > > > > "Streaming Commmand" is min 8ms "To complete reading all parameters
> > > > > > from NVM".
> > > > > > That would be a difference between probe and start_streaming, although
> > > > > > admittedly sending the mode and control setup I2C commands will take
> > > > > > up some of that time.
> > > > > > 
> > > > > > Plausibly the other set of modules don't have the NVM programmed and
> > > > > > hence they are ready sooner. Either way I'd say that does mean the
> > > > > > driver currently isn't following the defined power up sequence, and
> > > > > > the patch looks reasonable for IMX577.
> > > > > > However as this is a shared driver does IMX412 have this restriction
> > > > > > too? I can't find a datasheet for that one to check. For the sake of
> > > > > > ~9ms it's not going to make a huge difference though.
> > > > > > 
> > > > > >      Dave
> > > > > > 
> > > > > > [1] https://en.sunnywale.com/uploadfile/2021/1222/IMX577-AACK-C(Awin).pdf
> > > > > > 
> > > > > 
> > > > > Hi Dave,
> > > > > 
> > > > > this issue appears in the write register when streamon
> > > > > imx412_write_regs.  poweron->streamon.
> > > > > 
> > > > > static int imx412_start_streaming(struct imx412 *imx412)
> > > > > {
> > > > >            const struct imx412_reg_list *reg_list;
> > > > >            int ret;
> > > > > 
> > > > >            /* Write sensor mode registers */
> > > > >            reg_list = &imx412->cur_mode->reg_list;
> > > > >            ret = imx412_write_regs(imx412, reg_list->regs,
> > > > >                                    reg_list->num_of_regs);
> > > > >            if (ret) {
> > > > >                    dev_err(imx412->dev, "fail to write initial registers\n");
> > > > >                    return ret;
> > > > >            }
> > > > > 
> > > > >            /* Setup handler will write actual exposure and gain */
> > > > >            ret =  __v4l2_ctrl_handler_setup(imx412->sd.ctrl_handler);
> > > > >            if (ret) {
> > > > >                    dev_err(imx412->dev, "fail to setup handler\n");
> > > > >                    return ret;
> > > > >            }
> > > > > 
> > > > >            /* Delay is required before streaming*/
> > > > >            usleep_range(7400, 8000);
> > > > > 
> > > > >            /* Start streaming */
> > > > >            ret = imx412_write_reg(imx412, IMX412_REG_MODE_SELECT,
> > > > >                                   1, IMX412_MODE_STREAMING);
> > > > >            if (ret) {
> > > > >                    dev_err(imx412->dev, "fail to start streaming\n");
> > > > >                    return ret;
> > > > >            }
> > > > > 
> > > > >            return 0;
> > > > > }
> > > > >    > but T7 as the time before you can send "Streaming Commmand" is min 8ms "
> > > > > I think the usleep_range(7400, 8000) represents the 8ms duration
> > > > > required by T7.
> > > > 
> > > > I'd missed that one.
> > > > If you've delayed for 10-12ms between coming out of reset and sending
> > > > the first command, then does the Arducam module still require another
> > > > 8ms here, or can that be removed as you've already complied with T7?
> > > > 
> > > > Have you asked Arducam as to why their module takes longer? I can't
> > > > find an IMX577 module listed on their product pages so presumably it's
> > > > discontinued. There are a few links for a Luxonis Oak DepthAI board
> > > > [1] which is made by Arducam and is using IMX577, so is it that one?
> > > > Generally I've not encountered an issue with Arducam adding any weird
> > > > delay circuits on their sensor boards.
> > > > 
> > > >     Dave
> > > > 
> > > > [1] https://shop.luxonis.com/products/oak-ffc-imx577-m12
> > > > 
> > > > > Thanks,
> > > > > Wenmeng
> > > > > 
> > > > > 
> > > 
> > > Hi Dave,
> > > 
> > > Based on my testing, moving usleep_range(7400, 8000); to the beginning of
> > > the imx412_start_streaming function allows the Arducam IMX577 module to work
> > > properly. In contrast, other IMX577 sensors do not require this delay. I
> > > believe this corresponds to the T7 timing requirement. I have not yet
> > > confirmed this with Arducam, and I plan to compare once I receive another
> > > type Arducam IMX577 sensor.
> > 
> > Thanks for investigating this.
> > 
> > Have you checked how long it actually takes elsewhere (where the sensor
> > works) before the mode related registers are written (and when they start
> > being written) on systems where it actually works? As I²C writes require
> > sleeping and depend on a process getting scheduled a large number of times,
> > this might play a role here.
> > 
> > These patches might be useful in sensor drivers at large (but won't address
> > this problem)
> > <URL:https://git.retiisi.eu/?p=~sailus/linux.git;a=shortlog;h=refs/heads/pm-resume-delay>.
> > 
> 
> Hi Sakari,
> 
> Based on my testing, it takes about 6.5ms before the registers become
> writable. I believe this is not a CCI issue, because I have tested multiple
> platforms and only the Arducam 22-pin IMX577 shows this problem. This delay
> seems to correspond to the time required for T7. I made the following
> changes and ran multiple tests, and this approach works fine:
> 
> diff --git a/drivers/media/i2c/imx412.c b/drivers/media/i2c/imx412.c
> index 459cca36493e..5be698863653 100644
> --- a/drivers/media/i2c/imx412.c
> +++ b/drivers/media/i2c/imx412.c
> @@ -798,6 +798,9 @@ static int imx412_start_streaming(struct imx412 *imx412)
>         const struct imx412_reg_list *reg_list;
>         int ret;
> 
> +       /* Delay is required before streaming*/
> +       usleep_range(7400, 8000);
> +
>         /* Write sensor mode registers */
>         reg_list = &imx412->cur_mode->reg_list;
>         ret = imx412_write_regs(imx412, reg_list->regs,
> @@ -814,9 +817,6 @@ static int imx412_start_streaming(struct imx412 *imx412)
>                 return ret;
>         }
> 
> -       /* Delay is required before streaming*/
> -       usleep_range(7400, 8000);
> -
>         /* Start streaming */
>         ret = imx412_write_reg(imx412, IMX412_REG_MODE_SELECT,
>                                1, IMX412_MODE_STREAMING);
> 
> 
> From the perspective of the spec timing, I believe the above modification to
> the delay position is an acceptable change. What do you think?

Could you also add a comment explaining the issue? Otherwise there are good
chances someone will (at least try to) "fix" this later on.

-- 
Kind regards,

Sakari Ailus

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