netdev - Re: [PATCH] [PATCH v2] sh_eth: ensure pm_runtime cannot suspend the device during init

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Date:	Thu, 20 Mar 2014 12:55:29 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:	linux-kernel@...ts.codethink.co.uk, netdev@...r.kernel.org,
	linux-sh@...r.kernel.org, davem@...emloft.net,
	sergei.shtylyov@...entembedded.com,
	laurent.pinchart+renesas@...asonboard.com
Subject: Re: [PATCH] [PATCH v2] sh_eth: ensure pm_runtime cannot suspend the device during init

Hi Ben,

Thank you for the patch.

On Thursday 20 March 2014 10:33:27 Ben Dooks 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.
> 
> Another issue has also been found where the network device registration
> calls back into the driver thus causing further pm_runtime calls that
> also caused issues with the MDIO bus code.
> 
> Use pm_runtime_get_sync() and pm_runtime_put() 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>
> 
> ---
> Cc: sergei.shtylyov@...entembedded.com
> Cc: laurent.pinchart+renesas@...asonboard.com
> cc: netdev@...r.kernel.org
> 
> Note, Laurent this should probably be applied before your
> current series as it may require changes to the exit sequence.
> 
> Fixes from v1:
> 	- use pm_runtime_put() over pm_runtime_put_sync() as
> 	  we do not need to guaranteed the device has powered
>           off after probe.
> ---
>  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..955e422 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);
> 
>  	if (pdev->dev.of_node)
>  		pd = sh_eth_parse_dt(&pdev->dev);
> @@ -2961,6 +2961,7 @@ static int sh_eth_drv_probe(struct platform_device
> *pdev) pr_info("Base address at 0x%x, %pM, IRQ %d.\n",
>  		(u32)ndev->base_addr, ndev->dev_addr, ndev->irq);
> 
> +	pm_runtime_put(&pdev->dev);
>  	platform_set_drvdata(pdev, ndev);
> 
>  	return ret;

Don't you also need a pm_runtime_put() call in the error path at the end of 
the probe function ? I've had a quick look at the device core and there 
doesn't seem to be any automatic runtime PM cleanup performed when probe fails 
(I might have missed it though, so please double-check).

-- 
Regards,

Laurent Pinchart

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