linux-kernel - Re: [PATCH] pci/probe: Ignore the device id while handling CRS

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Date:	Mon, 22 Sep 2014 12:53:15 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Rajat Jain <rajatxjain@...il.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	rajatjain@...iper.net, groeck@...iper.net
Subject: Re: [PATCH] pci/probe: Ignore the device id while handling CRS

On Mon, Sep 08, 2014 at 02:19:49PM -0700, Rajat Jain wrote:
> Some root ports may return the actual device id returned by the
> endpoint, instead of faking up a synthetic id (0xFFFF) as specified
> by the PCIe spec (sec 2.3.2). We have seen such broken devices in the
> past that match this behaviour:
> (Ref: https://lkml.org/lkml/2007/11/1/198)
> 
> To take care of the same, CRS was disabled then, however, we want to
> enable CRS now (https://lkml.org/lkml/2014/9/2/509), but still do not
> want to break such devices. Thus check only against the
> (vendor id == 1) and ignore the device id.
> 
> Signed-off-by: Rajat Jain <rajatxjain@...il.com>
> Signed-off-by: Rajat Jain <rajatjain@...iper.net>
> Signed-off-by: Guenter Roeck <groeck@...iper.net>

Applied to pci/enumeration for v3.18, thanks!

> ---
>  drivers/pci/probe.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 3c4c35c..0076a9b 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1305,8 +1305,13 @@ bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
>  	    *l == 0x0000ffff || *l == 0xffff0000)
>  		return false;
>  
> -	/* Configuration request Retry Status */
> -	while (*l == 0xffff0001) {
> +	/*
> +	 * Configuration request Retry Status. Note that some root ports
> +	 * are broken and may return actual device ID instead of a synthetic ID
> +	 * (0xFFFF) to be faked as per the PCIe spec. Hence ignore the device ID
> +	 * and only check for (vendor id == 1)
> +	 */
> +	while (*l & 0xffff == 0x0001) {
>  		if (!crs_timeout)
>  			return false;
>  
> -- 
> 1.7.9.5
> 
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