netdev - Re: [PATCH v4 4/4] net: ethernet: ti: davinci_mdio: Deferring probe when soc_device

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Message-ID: <c3ded2b8-cf99-36ac-7152-5a23245a2e9c@ti.com>
Date:   Wed, 23 Nov 2022 21:29:15 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Nicolas Frayer <nfrayer@...libre.com>, <nm@...com>,
        <ssantosh@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <peter.ujfalusi@...il.com>,
        <vkoul@...nel.org>, <dmaengine@...r.kernel.org>,
        <grygorii.strashko@...com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <linux-omap@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     <khilman@...libre.com>, <glaroque@...libre.com>
Subject: Re: [PATCH v4 4/4] net: ethernet: ti: davinci_mdio: Deferring probe
 when soc_device_match() returns NULL

Hi Nicolas,

On 08/11/22 11:41 pm, Nicolas Frayer wrote:
> When the k3 socinfo driver is built as a module, there is a possibility
> that it will probe after the davinci mdio driver. By deferring the mdio
> probe we allow the k3 socinfo to probe and register the
> soc_device_attribute structure needed by the mdio driver.
> 
> Signed-off-by: Nicolas Frayer <nfrayer@...libre.com>
> ---
>  drivers/net/ethernet/ti/davinci_mdio.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c
> index 946b9753ccfb..095198b6b7be 100644
> --- a/drivers/net/ethernet/ti/davinci_mdio.c
> +++ b/drivers/net/ethernet/ti/davinci_mdio.c
> @@ -533,6 +533,10 @@ static int davinci_mdio_probe(struct platform_device *pdev)
>  		const struct soc_device_attribute *soc_match_data;
>  
>  		soc_match_data = soc_device_match(k3_mdio_socinfo);
> +
> +		if (!soc_match_data)
> +			return -EPROBE_DEFER;

I dont think this is right way to detect if socinfo driver is probed.
Per documentation of soc_device_match() , function will return NULL if
it does not match any of the entries in k3_mdio_socinfo (ie if we are
running on any platforms other that ones in the list)

Note that this driver is used on TI's 32 bit SoCs too that dont even
have a k3-socinfo driver equivalent. In such case, this code will end up
probe deferring indefinitely.

> +
>  		if (soc_match_data && soc_match_data->data) {
>  			const struct k3_mdio_soc_data *socdata =
>  						soc_match_data->data;