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

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Date:   Wed, 23 Nov 2022 09:33:33 -0800
From:   Kevin Hilman <khilman@...libre.com>
To:     Vignesh Raghavendra <vigneshr@...com>,
        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:     glaroque@...libre.com
Subject: Re: [PATCH v4 4/4] net: ethernet: ti: davinci_mdio: Deferring probe
 when soc_device_match() returns NULL

Hi Vignesh,

Vignesh Raghavendra <vigneshr@...com> writes:

> 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.

Yes, you're right.  This is not the right solution and this patch should
be dropped. We'll need to have a deeper look at socinfo to figure out
if/how it could be configured to support a fully modular kernel.

Kevin