Messages in this thread | | | Subject | Re: [PATCH] drm/msm/a6xx: fix for kernels without CONFIG_NVMEM | From | Akhil P Oommen <> | Date | Mon, 22 Feb 2021 21:15:39 +0530 |
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On 2/19/2021 9:30 PM, Rob Clark wrote: > On Fri, Feb 19, 2021 at 2:44 AM Akhil P Oommen <akhilpo@codeaurora.org> wrote: >> >> On 2/18/2021 9:41 PM, Rob Clark wrote: >>> On Thu, Feb 18, 2021 at 4:28 AM Akhil P Oommen <akhilpo@codeaurora.org> wrote: >>>> >>>> On 2/18/2021 2:05 AM, Jonathan Marek wrote: >>>>> 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) >>>> >>>> Atleast on sc7180's gpu, using an unsupported FMAX breaks gmu. It won't >>>> be very obvious what went wrong when this happens! >>> >>> Ugg, ok.. >>> >>> I suppose we could select NVMEM, but not QFPROM, and then the case >>> where QFPROM is not enabled on platforms that have the speed-bin field >>> in DT will fail gracefully and all other platforms would continue on >>> happily? >>> >>> BR, >>> -R >> >> Sounds good to me. >> > > You probably should do a quick test with NVMEM enabled but QFPROM > disabled to confirm my theory, but I *think* that should work > > BR, > -R >
I tried it on an sc7180 device. The suggested combo (CONFIG_NVMEM + no CONFIG_QCOM_QFPROM) makes the gpu probe fail with error "failed to read speed-bin. Some OPPs may not be supported by hardware". This is good enough clue for the developer that he should fix the broken speedbin detection.
-Akhil.
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