linux-kernel - Re: [PATCH] xhci: Make debug message consistent with bus and port number

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Message-Id: <90D5B23E-B037-49D2-BD44-7F9B0B2FC155@canonical.com>
Date:   Thu, 7 May 2020 15:58:36 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     mathias.nyman@...el.com,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xhci: Make debug message consistent with bus and port
 number



> On May 7, 2020, at 15:31, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> On Thu, May 07, 2020 at 03:15:01PM +0800, Kai-Heng Feng wrote:
>> 
>> 
>>> On May 7, 2020, at 14:45, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
>>> 
>>> On Thu, May 07, 2020 at 02:17:55PM +0800, Kai-Heng Feng wrote:
>>>> Current xhci debug message doesn't always output bus number, so it's
>>>> hard to figure out it's from USB2 or USB3 root hub.
>>>> 
>>>> In addition to that, some port numbers are offset to 0 and others are
>>>> offset to 1. Use the latter to match the USB core.
>>>> 
>>>> So use "bus number - port index + 1" to make debug message consistent.
>>>> 
>>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>>>> ---
>>>> drivers/usb/host/xhci-hub.c | 41 +++++++++++++++++++++----------------
>>>> 1 file changed, 23 insertions(+), 18 deletions(-)
>>>> 
>>>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
>>>> index f37316d2c8fa..83088c262cc4 100644
>>>> --- a/drivers/usb/host/xhci-hub.c
>>>> +++ b/drivers/usb/host/xhci-hub.c
>>>> @@ -1241,7 +1241,8 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
>>>> 			temp = readl(ports[wIndex]->addr);
>>>> 			/* Disable port */
>>>> 			if (link_state == USB_SS_PORT_LS_SS_DISABLED) {
>>>> -				xhci_dbg(xhci, "Disable port %d\n", wIndex);
>>>> +				xhci_dbg(xhci, "Disable port %d-%d\n",
>>>> +					 hcd->self.busnum, wIndex + 1);
>>> 
>>> Shouldn't xhci_dbg() show the bus number already?  
>> 
>> It's the PCI bus number, different to USB2/USB3 root hub bus number...
> 
> But if this is using dev_dbg(), and it is, then you know how to look
> that up by seeing where that device is in sysfs at that point in time.
> 
> So why add this again?

xHCI has two HCD, one for USB2 and one for USB3.
If both of their port with same number are in use, for instance, port 1, then they are port 1-1 and port 2-1.
Right now the debug message only show "Port 1", we still can't find the corresponding port via sysfs with insufficient info.

> 
>>> If not, please fix
>>> that up there instead of having to add it to all messages "by hand".
>> 
>> Not all xhci debug messages need roothub number in it.
> 
> Why pick these random ones?  What makes these different?

It's not random. We do it when there's a port in message.
Being able to know the exact port like "port 1-1" or "port 2-1", instead of just "port 1", can be really helpful.

Kai-Heng

> 
> Either all or none, be consistant please.
> 
> greg k-h