Re: [PATCH] drm/msm/a6xx: fix for kernels without CONFIG_NVMEM
From: Akhil P Oommen
Date: Mon Feb 22 2021 - 10:46:51 EST
On 2/19/2021 9:30 PM, Rob Clark wrote:
On Fri, Feb 19, 2021 at 2:44 AM Akhil P Oommen <akhilpo@xxxxxxxxxxxxxx> wrote:
On 2/18/2021 9:41 PM, Rob Clark wrote:
On Thu, Feb 18, 2021 at 4:28 AM Akhil P Oommen <akhilpo@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx> 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@xxxxxxxx>
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@xxxxxxxx>
---
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.