linux-kernel - Re: [PATCH] [media] solo6x10: avoid delayed register write

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Message-ID: <20161017195257.GD21569@stationary.pb.com>
Date:   Mon, 17 Oct 2016 20:52:57 +0100
From:   Andrey Utkin <andrey_utkin@...tmail.com>
To:     mchehab@...pensource.com, hverkuil@...all.nl
Cc:     ismael@...ev.co.uk, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, maintainers@...echerrydvr.com,
        andrey.utkin@...p.bluecherry.net
Subject: Re: [PATCH] [media] solo6x10: avoid delayed register write

On Thu, Sep 22, 2016 at 03:03:31AM +0300, Andrey Utkin wrote:
> This fixes a lockup at device probing which happens on some solo6010
> hardware samples. This is a regression introduced by commit e1ceb25a1569
> ("[media] SOLO6x10: remove unneeded register locking and barriers")
> 
> The observed lockup happens in solo_set_motion_threshold() called from
> solo_motion_config().
> 
> This extra "flushing" is not fundamentally needed for every write, but
> apparently the code in driver assumes such behaviour at last in some
> places.
> 
> Actual fix was proposed by Hans Verkuil.
> 
> Signed-off-by: Andrey Utkin <andrey.utkin@...p.bluecherry.net>
> ---
>  drivers/media/pci/solo6x10/solo6x10.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/media/pci/solo6x10/solo6x10.h b/drivers/media/pci/solo6x10/solo6x10.h
> index 5bd4987..3f8da5e 100644
> --- a/drivers/media/pci/solo6x10/solo6x10.h
> +++ b/drivers/media/pci/solo6x10/solo6x10.h
> @@ -284,7 +284,10 @@ static inline u32 solo_reg_read(struct solo_dev *solo_dev, int reg)
>  static inline void solo_reg_write(struct solo_dev *solo_dev, int reg,
>  				  u32 data)
>  {
> +	u16 val;
> +
>  	writel(data, solo_dev->reg_base + reg);
> +	pci_read_config_word(solo_dev->pdev, PCI_STATUS, &val);
>  }
>  
>  static inline void solo_irq_on(struct solo_dev *dev, u32 mask)
> -- 
> 2.9.2
> 

Mauro, Hans,
Please pick this up. This has been around for a month, I expected it
would get to v4.9-rc1 easily.
Thanks.