netdev - Re: [PATCH] sh_eth: ensure pm_runtime cannot suspend the device during init

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Date:	Tue, 18 Mar 2014 01:30:26 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>
CC:	linux-sh@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sh_eth: ensure pm_runtime cannot suspend the device during
 init

Hello.

On 03/17/2014 11:23 PM, Laurent Pinchart wrote:

>> The pm_rumtime work queue is causing the device to be suspended during
>> initialisation, thus the initialisation may not be able to access registers
>> properly. As the code is called from a work queue, it is possible that this
>> is not seen from certain configurations/builds due to the asynchronos
>> nature of the code.

>> Use pm_runtime_get_sync() and pm_runtime_put_sync() to ensure that the
>> pm system does not suspend it during the probe() call and remove the
>> now unnecessary pm_runtime_resume() call.

>> This fixes the external abort that can cause /sbin/init or other such
>> init processed to die.

>> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
>> Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> ---
>>   drivers/net/ethernet/renesas/sh_eth.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)

>> diff --git a/drivers/net/ethernet/renesas/sh_eth.c
>> b/drivers/net/ethernet/renesas/sh_eth.c index 4f76b5e..f1cfd64 100644
>> --- a/drivers/net/ethernet/renesas/sh_eth.c
>> +++ b/drivers/net/ethernet/renesas/sh_eth.c
>> @@ -2869,7 +2869,7 @@ static int sh_eth_drv_probe(struct platform_device
>> *pdev) spin_lock_init(&mdp->lock);
>>   	mdp->pdev = pdev;
>>   	pm_runtime_enable(&pdev->dev);
>> -	pm_runtime_resume(&pdev->dev);
>> +	pm_runtime_get_sync(&pdev->dev);

> Now that we've found out that the problem is caused by registering the network
> device before registering the mdio bus, shouldn't the proper solution be to
> register the network device last in the probe function ?

    Unfortunately, it's not easy to do, as sh_mdio_init() uses net_device::dev.
Probably could get rid of that use by partly reverting my managed device API 
patch since the only user seems to be devm_kzalloc() in that function, at 
least I hope so... still looking into this.
    BTW, quite many drivers have the same problem, doing different things 
after register_netdev() call, many of them probing MDIO as well.

WBR, Sergei

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