linux-kernel - Re: [PATCH v3] clk: imx8qxp: Defer instead of failing probe

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Message-ID:
 <DU0PR01MB93828BA400376EB1D6EEBDA19D9C2@DU0PR01MB9382.eurprd01.prod.exchangelabs.com>
Date: Wed, 4 Sep 2024 06:47:45 +0000
From: Diogo Manuel Pais Silva <diogo.pais@...ontrol.com>
To: Peng Fan <peng.fan@....com>, Abel Vesa <abel.vesa@...aro.org>
CC: "abelvesa@...nel.org" <abelvesa@...nel.org>,
        "linux-clk@...r.kernel.org"
	<linux-clk@...r.kernel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "s.hauer@...gutronix.de"
	<s.hauer@...gutronix.de>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        "sboyd@...nel.org"
	<sboyd@...nel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>,
        "EMC: linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] clk: imx8qxp: Defer instead of failing probe

Hi Peng,

Thanks for pointing that out, I missed it. I will submit a v4.
Yes, the issue only happens when fw_devlink is disabled. I believe this is because devlink generates the device dependency graphs and only probes this device when all the dependencies are met. When the devlink is disabled this dependency is not respect as far as probing order goes, so it can happen that the device is probed when the clock parent is yet to be probed.

Best regards,
Diogo Silva
________________________________________
From: Peng Fan <peng.fan@....com>
Sent: Wednesday, September 4, 2024 4:03 AM
To: Diogo Manuel Pais Silva; Abel Vesa
Cc: abelvesa@...nel.org; linux-clk@...r.kernel.org; shawnguo@...nel.org; kernel@...gutronix.de; s.hauer@...gutronix.de; linux-arm-kernel@...ts.infradead.org; sboyd@...nel.org; mturquette@...libre.com; festevam@...il.com; imx@...ts.linux.dev; EMC: linux-kernel@...r.kernel.org
Subject: RE: [PATCH v3] clk: imx8qxp: Defer instead of failing probe

Hi Diogo,

> Subject: [PATCH v3] clk: imx8qxp: Defer instead of failing probe
>
> When of_clk_parent_fill is ran without all the parent clocks having
> been probed then the probe function will return -EINVAL, making it so
> that the probe isn't attempted again. As fw_devlink is on by default
> this does not usually happen, but if fw_devlink is disabled then it is
> very possible that the parent clock will be probed after the lpcg first
> attempt.

Did you meet issue with fw_devlink disabled?

>
> Signed-off-by: Diogo Silva <diogo.pais@...ontrol.com>
> ---
> v2: change from dev_warn to dev_err_probe
> v3: refresh patch
> ---
>  drivers/clk/imx/clk-imx8qxp-lpcg.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/imx/clk-imx8qxp-lpcg.c b/drivers/clk/imx/clk-
> imx8qxp-lpcg.c
> index d0ccaa040225..cae8f6060fe8 100644
> --- a/drivers/clk/imx/clk-imx8qxp-lpcg.c
> +++ b/drivers/clk/imx/clk-imx8qxp-lpcg.c
> @@ -225,8 +225,8 @@ static int imx_lpcg_parse_clks_from_dt(struct
> platform_device *pdev,
>
>         ret = of_clk_parent_fill(np, parent_names, count);
>         if (ret != count) {
> -               dev_err(&pdev->dev, "failed to get clock parent names\n");
> -               return count;
> +               return dev_err_probe(&pdev->dev, -EPROBE_DEFER,
> +                                    "failed to get all clock parent
> + names\n");
>         }

The change is not enough, you also need to handle
        ret = imx_lpcg_parse_clks_from_dt(pdev, np);
        if (!ret)
                return 0;
->
        ret = imx_lpcg_parse_clks_from_dt(pdev, np);
        if (!ret)
                return 0;
        if (ret == -EPROBE_DEFER)
                return ret;

Regards,
Peng.

>
>         ret = of_property_read_string_array(np, "clock-output-names",
> --
> 2.34.1
> ________________________________________
> From: Abel Vesa <abel.vesa@...aro.org>
> Sent: Wednesday, August 28, 2024 10:31 AM
> To: Diogo Manuel Pais Silva
> Cc: Peng Fan; abelvesa@...nel.org; linux-clk@...r.kernel.org;
> shawnguo@...nel.org; kernel@...gutronix.de;
> s.hauer@...gutronix.de; linux-arm-kernel@...ts.infradead.org;
> sboyd@...nel.org; mturquette@...libre.com; festevam@...il.com;
> imx@...ts.linux.dev; EMC: linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2] clk: imx8qxp: Defer instead of failing probe
>
> On 24-07-02 08:10:44, Diogo Manuel Pais Silva wrote:
> > When of_clk_parent_fill is ran without all the parent clocks having
> been probed then the probe function will return -EINVAL, making it so
> that the probe isn't attempted again. As fw_devlink is on by default
> this does not usually happen, but if fw_devlink is disabled then it is
> very possible that the parent clock will be probed after the lpcg first
> attempt.
> >
> > Signed-off-by: Diogo Silva <diogo.pais@...ontrol.com>
>
> This patch doesn't apply cleanly.
>
> Please respin.
>
> Thanks!
>
> > ---
> > v2: change from dev_warn to dev_err_probe
> > ---
> >  drivers/clk/imx/clk-imx8qxp-lpcg.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/clk/imx/clk-imx8qxp-lpcg.c
> > b/drivers/clk/imx/clk-imx8qxp-lpcg.c
> > index d0ccaa040225..7bd9b745edbe 100644
> > --- a/drivers/clk/imx/clk-imx8qxp-lpcg.c
> > +++ b/drivers/clk/imx/clk-imx8qxp-lpcg.c
> > @@ -225,8 +225,8 @@ static int
> imx_lpcg_parse_clks_from_dt(struct
> > platform_device *pdev,
> >
> >       ret = of_clk_parent_fill(np, parent_names, count);
> >       if (ret != count) {
> > -             dev_err(&pdev->dev, "failed to get clock parent names\n");
> > -             return count;
> > +             return dev_err_probe(&pdev->dev, -EPROBE_DEFER,
> > +                             "failed to get all clock parent
> > + names\n");
> >       }
> >
> >       ret = of_property_read_string_array(np, "clock-output-names",
> > --
> > 2.34.1
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