From: Jonathan Marek <jonathan@marek.ca>
To: Rob Clark <robdclark@gmail.com>,
Akhil P Oommen <akhilpo@codeaurora.org>,
freedreno <freedreno@lists.freedesktop.org>,
Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel@ffwll.ch>,
Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Eric Anholt <eric@anholt.net>,
Sharat Masetty <smasetty@codeaurora.org>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<linux-arm-msm@vger.kernel.org>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<dri-devel@lists.freedesktop.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/msm/a6xx: fix for kernels without CONFIG_NVMEM
Date: Wed, 17 Feb 2021 15:35:09 -0500 [thread overview]
Message-ID: <74d1277e-295f-0996-91c3-05cfce8d3a0e@marek.ca> (raw)
In-Reply-To: <CAF6AEGsHws23ozeJ8G23LFQ8J=CVVrx5xvkSgBuE_uSwT4YurQ@mail.gmail.com>
On 2/17/21 3:18 PM, Rob Clark wrote:
> On Wed, Feb 17, 2021 at 11:08 AM Jordan Crouse <jcrouse@codeaurora.org> wrote:
>>
>> On Wed, Feb 17, 2021 at 07:14:16PM +0530, Akhil P Oommen wrote:
>>> On 2/17/2021 8:36 AM, Rob Clark wrote:
>>>> On Tue, Feb 16, 2021 at 12:10 PM Jonathan Marek <jonathan@marek.ca> wrote:
>>>>>
>>>>> Ignore nvmem_cell_get() EOPNOTSUPP error in the same way as a ENOENT error,
>>>>> to fix the case where the kernel was compiled without CONFIG_NVMEM.
>>>>>
>>>>> Fixes: fe7952c629da ("drm/msm: Add speed-bin support to a618 gpu")
>>>>> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
>>>>> ---
>>>>> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 6 +++---
>>>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> index ba8e9d3cf0fe..7fe5d97606aa 100644
>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> @@ -1356,10 +1356,10 @@ static int a6xx_set_supported_hw(struct device *dev, struct a6xx_gpu *a6xx_gpu,
>>>>>
>>>>> cell = nvmem_cell_get(dev, "speed_bin");
>>>>> /*
>>>>> - * -ENOENT means that the platform doesn't support speedbin which is
>>>>> - * fine
>>>>> + * -ENOENT means no speed bin in device tree,
>>>>> + * -EOPNOTSUPP means kernel was built without CONFIG_NVMEM
>>>>
>>>> very minor nit, it would be nice to at least preserve the gist of the
>>>> "which is fine" (ie. some variation of "this is an optional thing and
>>>> things won't catch fire without it" ;-))
>>>>
>>>> (which is, I believe, is true, hopefully Akhil could confirm.. if not
>>>> we should have a harder dependency on CONFIG_NVMEM..)
>>> IIRC, if the gpu opp table in the DT uses the 'opp-supported-hw' property,
>>> we will see some error during boot up if we don't call
>>> dev_pm_opp_set_supported_hw(). So calling "nvmem_cell_get(dev, "speed_bin")"
>>> is a way to test this.
>>>
>>> If there is no other harm, we can put a hard dependency on CONFIG_NVMEM.
>>
>> I'm not sure if we want to go this far given the squishiness about module
>> dependencies. As far as I know we are the only driver that uses this seriously
>> on QCOM SoCs and this is only needed for certain targets. I don't know if we
>> want to force every target to build NVMEM and QFPROM on our behalf. But maybe
>> I'm just saying that because Kconfig dependencies tend to break my brain (and
>> then Arnd has to send a patch to fix it).
>>
>
> Hmm, good point.. looks like CONFIG_NVMEM itself doesn't have any
> other dependencies, so I suppose it wouldn't be the end of the world
> to select that.. but I guess we don't want to require QFPROM
>
> I guess at the end of the day, what is the failure mode if you have a
> speed-bin device, but your kernel config misses QFPROM (and possibly
> NVMEM)? If the result is just not having the highest clk rate(s)
> available, that isn't the end of the world. But if it makes things
> not-work, that is sub-optimal. Generally, especially on ARM, kconfig
> seems to be way harder than it should be to build a kernel that works,
> if we could somehow not add to that problem (for both people with a6xx
> and older gens) that would be nice ;-)
>
There is a "imply" kconfig option which solves exactly this problem.
(you would "imply NVMEM" instead of "select NVMEM". then it would be
possible to disable NVMEM but it would get enabled by default)
> BR,
> -R
>
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next prev parent reply other threads:[~2021-02-17 20:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-16 20:09 [PATCH] drm/msm/a6xx: fix for kernels without CONFIG_NVMEM Jonathan Marek
2021-02-17 3:06 ` Rob Clark
2021-02-17 13:44 ` Akhil P Oommen
2021-02-17 19:08 ` Jordan Crouse
2021-02-17 20:18 ` Rob Clark
2021-02-17 20:35 ` Jonathan Marek [this message]
2021-02-18 12:28 ` Akhil P Oommen
2021-02-18 16:11 ` Rob Clark
2021-02-19 10:44 ` Akhil P Oommen
2021-02-19 16:00 ` Rob Clark
2021-02-22 15:45 ` Akhil P Oommen
2021-02-22 16:06 ` Rob Clark
2021-04-01 20:12 ` Rob Clark
2021-04-01 21:03 ` Dmitry Baryshkov
2021-04-01 21:49 ` Rob Clark
2021-04-03 4:39 ` Akhil P Oommen
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