linux-kernel - Re: [PATCH 02/12] drm/nouveau/timer: skip calibration on GK20A

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Message-ID: <CACAvsv7gsRrXAk-=M08hjvhrRWvi80wrgRAp1M5T66zMa5ydtA@mail.gmail.com>
Date:	Mon, 14 Apr 2014 18:35:35 +1000
From:	Ben Skeggs <skeggsb@...il.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	Thierry Reding <thierry.reding@...il.com>,
	"nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Ben Skeggs <bskeggs@...hat.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 02/12] drm/nouveau/timer: skip calibration on GK20A

On Fri, Apr 11, 2014 at 5:34 PM, Alexandre Courbot <acourbot@...dia.com> wrote:
> On 04/11/2014 04:31 PM, Ben Skeggs wrote:
>>
>> On Fri, Apr 11, 2014 at 12:46 PM, Alexandre Courbot <gnurou@...il.com>
>> wrote:
>>>
>>> On Wed, Mar 26, 2014 at 1:19 PM, Ben Skeggs <skeggsb@...il.com> wrote:
>>>>
>>>> On Tue, Mar 25, 2014 at 7:54 AM, Thierry Reding
>>>> <thierry.reding@...il.com> wrote:
>>>>>
>>>>> On Mon, Mar 24, 2014 at 05:42:24PM +0900, Alexandre Courbot wrote:
>>>>>>
>>>>>> GK20A's timer is directly attached to the system timer and cannot be
>>>>>> calibrated. Skip the calibration phase on that chip since the
>>>>>> corresponding registers do not exist.
>>>>>>
>>>>>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>>>>>> ---
>>>>>>   drivers/gpu/drm/nouveau/core/subdev/timer/nv04.c | 19
>>>>>> +++++++++++++------
>>>>>>   1 file changed, 13 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/nouveau/core/subdev/timer/nv04.c
>>>>>> b/drivers/gpu/drm/nouveau/core/subdev/timer/nv04.c
>>>>>> index c0bdd10358d7..822fe0d8a871 100644
>>>>>> --- a/drivers/gpu/drm/nouveau/core/subdev/timer/nv04.c
>>>>>> +++ b/drivers/gpu/drm/nouveau/core/subdev/timer/nv04.c
>>>>>> @@ -185,6 +185,10 @@ nv04_timer_init(struct nouveau_object *object)
>>>>>>        if (ret)
>>>>>>                return ret;
>>>>>>
>>>>>> +     /* gk20a does not have the calibration registers */
>>>>>> +     if (device->chipset == 0xea)
>>>>>> +             goto skip_clk_init;
>>>>>
>>>>>
>>>>> I'm concerned that this won't scale in the future. Perhaps a better
>>>>> solution would be to add a "flags" or "features" field to struct
>>>>> nouveau_device along with feature bits such as HAS_CALIBRATION or
>>>>> similar.
>>>>>
>>>>> That way we don't have to touch this code for every new future Tegra
>>>>> chip. Unless perhaps if there's a reason to expect things to change in
>>>>> newer generations.
>>>>
>>>> I've already handled this in a slightly different way in the tree I'd
>>>> previously pointed Alex at (I think!), as I needed to do the same for
>>>> GM107.
>>>>
>>>> Should just be able to use that implementation (so, just change the
>>>> probe patch) here too.
>>>
>>>
>>> I will skip this patch and use your implementation then. Btw,
>>> shouldn't the source file for the GK20A implementation be named nvea.c
>>> instead of gk20a.c?
>>
>> For the Maxwell stuff I've been using "gm107" now too.  Since we're
>> working with you guys these days it seems better to use the same names
>> for things ;)
>
>
> So would you like us to use the same naming scheme as well? So far all my
> patches use "nvea.c" whenever I need to add code.
If it's not too much of a problem at this point, then that'd be good.
Right before I send -next for the next merge window I'll likely do a
mass rename anyway, so if we can get your patches merged before then
(which would be really good!), it doesn't matter much.

Ben.
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