linux-kernel - Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set

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Message-Id: <20061013214135.8fbc9f04.akpm@osdl.org>
Date:	Fri, 13 Oct 2006 21:41:35 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Val Henson <val_henson@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>, netdev@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set

On Fri, 06 Oct 2006 13:05:18 -0600
Matthew Wilcox <matthew@....cx> wrote:

> Since some devices may not implement the MWI bit, we should check that
> the write did set it and return an error if it didn't.
> 
> Signed-off-by: Matthew Wilcox <matthew@....cx>
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index a544997..3d041f4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -900,13 +900,17 @@ #endif
>  		return rc;
>  
>  	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> -	if (! (cmd & PCI_COMMAND_INVALIDATE)) {
> -		pr_debug("PCI: Enabling Mem-Wr-Inval for device %s\n", pci_name(dev));
> -		cmd |= PCI_COMMAND_INVALIDATE;
> -		pci_write_config_word(dev, PCI_COMMAND, cmd);
> -	}
> -	
> -	return 0;
> +	if (cmd & PCI_COMMAND_INVALIDATE)
> +		return 0;
> +
> +	pr_debug("PCI: Enabling Mem-Wr-Inval for device %s\n", pci_name(dev));
> +	cmd |= PCI_COMMAND_INVALIDATE;
> +	pci_write_config_word(dev, PCI_COMMAND, cmd);
> +
> +	/* read result from hardware (in case bit refused to enable) */
> +	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> +
> +	return (cmd & PCI_COMMAND_INVALIDATE) ? 0 : -EINVAL;
>  }
>  
>  /**

Bisection shows that this patch
(pci-check-that-mwi-bit-really-did-get-set.patch in Greg's PCI tree) breaks
suspend-to-disk on my Vaio.  It writes the suspend image and gets to the
point where it's supposed to power down, but doesn't.

After a manual power-cycle it successfully resumes from disk, but
networking (at least) is dead.

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