Re: [PATCH v2 06/14] drm/msm/gpu: Use dev_pm_opp_set_rate for non-GMU GPUs
From: Dmitry Baryshkov
Date: Sat Feb 18 2023 - 11:52:16 EST
On 18/02/2023 13:04, Konrad Dybcio wrote:
On 17.02.2023 22:07, Dmitry Baryshkov wrote:
On 14/02/2023 19:31, Konrad Dybcio wrote:
Currently we only utilize the OPP table connected to the GPU for
getting (available) frequencies. We do however need to scale the
voltage rail(s) accordingly to ensure that we aren't trying to
run the GPU at 1GHz with a VDD_LOW vote, as that would result in
an otherwise inexplainable hang.
Tell the OPP framework that we want to scale the "core" clock
and swap out the clk_set_rate to a dev_pm_opp_set_rate in
msm_devfreq_target() to enable usage of required-opps and by
extension proper voltage level/corner scaling.
Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
---
drivers/gpu/drm/msm/adreno/adreno_gpu.c | 4 ++++
drivers/gpu/drm/msm/msm_gpu_devfreq.c | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index ce6b76c45b6f..15e405e4f977 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -1047,6 +1047,10 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
const char *gpu_name;
u32 speedbin;
+ /* This can only be done here, or devm_pm_opp_set_supported_hw will WARN_ON() */
+ if (!IS_ERR(devm_clk_get(dev, "core")))
+ devm_pm_opp_set_clkname(dev, "core");
Can we instead move a call to a6xx_set_supported_hw() / check_speed_bin after the adreno_gpu_init() ? It will call msm_gpu_init, which in turn sets gpu->core_clk.
Ideally you can call devm_pm_opp_set_clkname() from that function.
Or maybe completely drop gpu->core_clk and always use devm_pm_opp_set_clk_rate().
That would break non-OPP targets, last of which were probably added N=big years ago..
No. In the lack of OPP tables, dev_pm_opp_clk_set_rate() should behave
exactly like the clk_set_rate().
I'm not sure these would still work, as I think we've got rid of some ugly
clock getters that were looking for both "core" and "core_clk" etc.
We still support core vs core_clk, see the get_clocks() at msm_gpu.c and
then msm_clk_bulk_get_clock(). However we might mimick this function and
call devm_pm_opp_set_clkname() with the proper name ("core" or "core_clk").
See 8db0b6c7b636376789e356d861c3c6c35dcb6913 for what seems to be the most recent
example of non-OPP.
IMX51/53 also have no OPP tables and are using the (AFAIK) now-defunct _clk-suffixed
clock-names.
It works, I tested it during this cycle.
I'd be more than happy to rip out some of this legacy code and convert it
to something modern like OPP, but I'm not sure you guys would like it considering
the breakage on (arguably ancient and borderline retired) platforms.
I think, we should try switching to OPP-for-everybody, granted the
promise of dev_pm_opp_set_clk_rate() being backwards compatible with
bare clk_set_rate().
This patch as-is "only" breaks non-OPP a5xx & a6xx (as they have .gpu_busy defined),
of which there are none..
+
adreno_gpu->funcs = funcs;
adreno_gpu->info = adreno_info(config->rev);
adreno_gpu->gmem = adreno_gpu->info->gmem;
diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index e27dbf12b5e8..ea70c1c32d94 100644
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -48,7 +48,7 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
gpu->funcs->gpu_set_freq(gpu, opp, df->suspended);
mutex_unlock(&df->lock);
} else {
- clk_set_rate(gpu->core_clk, *freq);
+ dev_pm_opp_set_rate(dev, *freq);
This is not enough, there are calls to clk_set_rate(gpu->core_clk) in msm_gpu.c which are called from the suspend/resume path.
Right, good catch.
Konrad
}
dev_pm_opp_put(opp);
--
With best wishes
Dmitry