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

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Message-ID: <CACAvsv54BF3cD6y59=kQ=1j-S9tGixTz_J3gx2mbOEkB2eQ4cA@mail.gmail.com>
Date:	Wed, 26 Mar 2014 14:19:49 +1000
From:	Ben Skeggs <skeggsb@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Alexandre Courbot <gnurou@...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 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.

Thanks,
Ben.

>
> Thierry
>
> _______________________________________________
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> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>
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