Re: [PATCH v2] dwc: dra7xx: Print link state to console for debug

From: Kishon Vijay Abraham I
Date: Tue Oct 24 2017 - 02:18:25 EST


Hi Bjorn,

On Monday 23 October 2017 07:34 PM, Bjorn Helgaas wrote:
> On Mon, Oct 23, 2017 at 03:59:49PM +0530, Faiz Abbas wrote:
>> On Saturday 21 October 2017 04:39 AM, Bjorn Helgaas wrote:
>>> On Thu, Oct 19, 2017 at 06:13:29PM +0530, Faiz Abbas wrote:
>>>> Enable support for printing the LTSSM link state for debugging PCI
>>>> when link is down.
>>>>
>>>> Signed-off-by: Faiz Abbas <faiz_abbas@xxxxxx>
>>>> ---
>>>> v2:
>>>> 1. Changed dev_err() to dev_dbg()
>>>> 2. Changed static char array to static const char * const
>>>> 3. format changes
>>>
>>> I'm not really sure how much debug help we want to carry around in the
>>> mainline kernel. End users aren't going to use this; it seems like
>>> more of a lab tool, and in situations like that you usually end up
>>> carrying around some out-of-tree patches for a while anyway. But I
>>> can probably be convinced either way.
>>
>> It'll be easier to support customers if they can tell us what the state
>> of the link is by just changing the log level. We won't have to send a
>> debug patch to the customer to find that out.
>
> That still sounds like a lab debug situation to me. Regular customers
> do not debug things at the level of the link state. I'm not aware of
> any other drivers that do this, so including this hints that this
> driver/hardware is not very mature.
>
> Printing text certainly *looks* nice, but it adds a lot of code and
> I'm not sure how much actual value they add. Just printing a hex
> value might be more reliable in terms of communicating it accurately
> back to you. E.g., it might be easier to lose the distinction between
> DISABLED_ENTRY and DISABLED_IDLE than between 0x745f and 0x7463,
> especially in a phone situation.
>
> Anyway, if Kishon acks this, I'll apply it. One nit: please do the
> "link up" test once, e.g.,

IMHO both print text and the debug print itself helps to save developer effort.

FWIW:
Acked-by: Kishon Vijay Abraham I <kishon@xxxxxx>

Thanks
Kishon