linux-kernel - Re: [PATCH v2] soc: imx: imx8m-blk-ctrl: Defer probe if 'bus' genpd is not yet ready

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Date:   Tue, 13 Sep 2022 12:21:59 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com
Cc:     kernel@...labora.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] soc: imx: imx8m-blk-ctrl: Defer probe if 'bus' genpd
 is not yet ready

Hello Benjamin,

On 13.09.22 12:17, Benjamin Gaignard wrote:
> Depending of the boot sequence 'bus' genpd could be probed after imx8m-blk-ctrl
> which led driver probe to fail. Change the returned error to allow
> to defer the probe in this case.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> ---
> v2:
> - keep dev_err_probe only change the return value
>  
>  drivers/soc/imx/imx8m-blk-ctrl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/imx/imx8m-blk-ctrl.c b/drivers/soc/imx/imx8m-blk-ctrl.c
> index dff7529268e4..253d08de8923 100644
> --- a/drivers/soc/imx/imx8m-blk-ctrl.c
> +++ b/drivers/soc/imx/imx8m-blk-ctrl.c
> @@ -215,9 +215,10 @@ static int imx8m_blk_ctrl_probe(struct platform_device *pdev)
>  
>  	bc->bus_power_dev = genpd_dev_pm_attach_by_name(dev, "bus");
>  	if (IS_ERR(bc->bus_power_dev))
> -		return dev_err_probe(dev, PTR_ERR(bc->bus_power_dev),
> +		return dev_err_probe(dev, -EPROBE_DEFER,
>  				     "failed to attach power domain \"bus\"\n");

Close, but now any error is treated as an -EPROBE_DEFER, e.g. -ENOMEM.
Please check which error code is returned for your corner case
and see if either the API should be changed to return -EPROBE_DEFER
instead or if you should translate only that error code on the consumer
side to -EPROBE_DEFER.

Thanks,
Ahmad

>  
> +
>  	for (i = 0; i < bc_data->num_domains; i++) {
>  		const struct imx8m_blk_ctrl_domain_data *data = &bc_data->domains[i];
>  		struct imx8m_blk_ctrl_domain *domain = &bc->domains[i];


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