linux-kernel - Re: [PATCH] usb: xhci: Enable LPM for VIA LABS VL805

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Date:   Tue, 11 Feb 2020 14:13:09 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>
Cc:     linux-usb@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: xhci: Enable LPM for VIA LABS VL805

On 11.2.2020 12.02, Nicolas Saenz Julienne wrote:
> Hi Stefan, Mathias.
> 
> On Tue, 2020-02-11 at 10:49 +0100, Stefan Wahren wrote:
>> Hi Mathias,
>>
>> On 11.02.20 10:34, Mathias Nyman wrote:
>>> On 10.2.2020 20.59, Greg Kroah-Hartman wrote:
>>>> On Mon, Jan 20, 2020 at 03:24:22PM +0100, Nicolas Saenz Julienne wrote:
>>>>> This PCIe controller chip is used on the Raspberry Pi 4 and multiple
>>>>> adapter cards. There is no publicly available documentation for the
>>>>> chip, yet both the downstream RPi4 kernel and the controller cards
>>>>> support/advertise LPM support.
>>>>>
>>>>> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>>>>> ---
>>>>>  drivers/usb/host/xhci-pci.c | 3 +++
>>>>>  1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
>>>>> index 4917c5b033fa..c1976e98992b 100644
>>>>> --- a/drivers/usb/host/xhci-pci.c
>>>>> +++ b/drivers/usb/host/xhci-pci.c
>>>>> @@ -241,6 +241,9 @@ static void xhci_pci_quirks(struct device *dev,
>>>>> struct xhci_hcd *xhci)
>>>>>  			pdev->device == 0x3432)
>>>>>  		xhci->quirks |= XHCI_BROKEN_STREAMS;
>>>>>  
>>>>> +	if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == 0x3483)
>>>>> +		xhci->quirks |= XHCI_LPM_SUPPORT;
>>>>> +
>>>>>  	if (pdev->vendor == PCI_VENDOR_ID_ASMEDIA &&
>>>>>  			pdev->device == 0x1042)
>>>>>  		xhci->quirks |= XHCI_BROKEN_STREAMS;
>>>> Mathias, is this in your review queue?
>>>>
>>> Ah yes, before adding link power management support for this controller we
>>> should check that it has sane (or any) exit latency values set in its
>>> HCSPARAMS3 capability register.
> 
> I did some checks myself before sending the patch, and tested with some devices
> I own. The latencies seemd reasonable. For example I just hooked up an USB3 HD,
> the root HUB exposes:
> 
> 	bU1DevExitLat           4 micro seconds
> 	bU2DevExitLat         231 micro seconds
> 
> And xhci configured the device with:
> 
> 	bU1DevExitLat          10 micro seconds
> 	bU2DevExitLat        2047 micro seconds
> 
>>> Nicolas, if you have this controller could you show the capability
>>> registers:
>>>
>>> cat /sys/kernel/debug/usb/xhci/*/reg-cap
> 
> CAPLENGTH = 0x01000020
> HCSPARAMS1 = 0x05000420
> HCSPARAMS2 = 0xfc000031
> HCSPARAMS3 = 0x00e70004

Thanks, looks sane, U1 Device exit latency is 4us, and U2 is 231us, and as
showed above these were set correctly to the roothub.

Greg, if you want you can pick this patch as is, otherwise I'll send it later
with other usb-next patches.

Acked-by: Mathias Nyman <mathias.nyman@...ux.intel.com>