linux-kernel - Re: [PATCH 1/2] usb: pci-quirks: Correct AMD PLL quirk detection

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Date:   Fri, 5 Jul 2019 15:04:28 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Ryan Kennedy <ryan5544@...il.com>
cc:     gregkh@...uxfoundation.org, <mathias.nyman@...el.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: pci-quirks: Correct AMD PLL quirk detection

On Thu, 4 Jul 2019, Ryan Kennedy wrote:

> The AMD PLL USB quirk is incorrectly enabled on newer Ryzen
> chipsets. The logic in usb_amd_find_chipset_info currently checks
> for unaffected chipsets rather than affected ones. This broke
> once a new chipset was added in e788787ef. It makes more sense
> to reverse the logic so it won't need to be updated as new
> chipsets are added. Note that the core of the workaround in
> usb_amd_quirk_pll does correctly check the chipset.
> 
> Signed-off-by: Ryan Kennedy <ryan5544@...il.com>
> ---
>  drivers/usb/host/pci-quirks.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 3ce71cbfbb58..ad05c27b3a7b 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -205,7 +205,7 @@ int usb_amd_find_chipset_info(void)
>  {
>  	unsigned long flags;
>  	struct amd_chipset_info info;
> -	int ret;
> +	int need_pll_quirk = 0;
>  
>  	spin_lock_irqsave(&amd_lock, flags);
>  
> @@ -219,21 +219,28 @@ int usb_amd_find_chipset_info(void)
>  	spin_unlock_irqrestore(&amd_lock, flags);
>  
>  	if (!amd_chipset_sb_type_init(&info)) {
> -		ret = 0;
>  		goto commit;
>  	}
>  
> -	/* Below chipset generations needn't enable AMD PLL quirk */
> -	if (info.sb_type.gen == AMD_CHIPSET_UNKNOWN ||
> -			info.sb_type.gen == AMD_CHIPSET_SB600 ||
> -			info.sb_type.gen == AMD_CHIPSET_YANGTZE ||
> -			(info.sb_type.gen == AMD_CHIPSET_SB700 &&
> -			info.sb_type.rev > 0x3b)) {
> +	switch (info.sb_type.gen) {
> +	case AMD_CHIPSET_SB700:
> +		need_pll_quirk = info.sb_type.rev <= 0x3B;
> +		break;
> +	case AMD_CHIPSET_SB800:
> +	case AMD_CHIPSET_HUDSON2:
> +	case AMD_CHIPSET_BOLTON:
> +		need_pll_quirk = 1;
> +		break;
> +	default:
> +		need_pll_quirk = 0;
> +		break;
> +	}
> +
> +	if (!need_pll_quirk) {
>  		if (info.smbus_dev) {
>  			pci_dev_put(info.smbus_dev);
>  			info.smbus_dev = NULL;
>  		}
> -		ret = 0;
>  		goto commit;
>  	}
>  
> @@ -252,7 +259,7 @@ int usb_amd_find_chipset_info(void)
>  		}
>  	}
>  
> -	ret = info.probe_result = 1;
> +	need_pll_quirk = info.probe_result = 1;
>  	printk(KERN_DEBUG "QUIRK: Enable AMD PLL fix\n");
>  
>  commit:
> @@ -263,7 +270,7 @@ int usb_amd_find_chipset_info(void)
>  
>  		/* Mark that we where here */
>  		amd_chipset.probe_count++;
> -		ret = amd_chipset.probe_result;
> +		need_pll_quirk = amd_chipset.probe_result;
>  
>  		spin_unlock_irqrestore(&amd_lock, flags);
>  
> @@ -277,7 +284,7 @@ int usb_amd_find_chipset_info(void)
>  		spin_unlock_irqrestore(&amd_lock, flags);
>  	}
>  
> -	return ret;
> +	return need_pll_quirk;
>  }
>  EXPORT_SYMBOL_GPL(usb_amd_find_chipset_info);

Acked-by: Alan Stern <stern@...land.harvard.edu>