Re: [PATCH] clk: qcom: gfx3d: add parent to parent request map

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 1/17/26 4:54 AM, Dmitry Baryshkov wrote:
> After commit d228ece36345 ("clk: divider: remove round_rate() in favor
> of determine_rate()") determining GFX3D clock rate crashes, because the
> passed parent map doesn't provide the expected best_parent_hw clock
> (with the roundd_rate path before the offending commit the
> best_parent_hw was ignored).
> 
> Set the field in parent_req in addition to setting it in the req,
> fixing the crash.
> 
>  clk_hw_round_rate (drivers/clk/clk.c:1764) (P)
>  clk_divider_bestdiv (drivers/clk/clk-divider.c:336)
>  divider_determine_rate (drivers/clk/clk-divider.c:358)
>  clk_alpha_pll_postdiv_determine_rate (drivers/clk/qcom/clk-alpha-pll.c:1275)
>  clk_core_determine_round_nolock (drivers/clk/clk.c:1606)
>  clk_core_round_rate_nolock (drivers/clk/clk.c:1701)
>  __clk_determine_rate (drivers/clk/clk.c:1741)
>  clk_gfx3d_determine_rate (drivers/clk/qcom/clk-rcg2.c:1268)
>  clk_core_determine_round_nolock (drivers/clk/clk.c:1606)
>  clk_core_round_rate_nolock (drivers/clk/clk.c:1701)
>  clk_core_round_rate_nolock (drivers/clk/clk.c:1710)
>  clk_round_rate (drivers/clk/clk.c:1804)
>  dev_pm_opp_set_rate (drivers/opp/core.c:1440 (discriminator 1))
>  msm_devfreq_target (drivers/gpu/drm/msm/msm_gpu_devfreq.c:51)
>  devfreq_set_target (drivers/devfreq/devfreq.c:360)
>  devfreq_update_target (drivers/devfreq/devfreq.c:426)
>  devfreq_monitor (drivers/devfreq/devfreq.c:458)
>  process_one_work (arch/arm64/include/asm/jump_label.h:36 include/trace/events/workqueue.h:110 kernel/workqueue.c:3284)
>  worker_thread (kernel/workqueue.c:3356 (discriminator 2) kernel/workqueue.c:3443 (discriminator 2))
>  kthread (kernel/kthread.c:467)
>  ret_from_fork (arch/arm64/kernel/entry.S:861)
> 
> Fixes: 55213e1acec9 ("clk: qcom: Add gfx3d ping-pong PLL frequency switching")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---

I'm still not fully understanding the logic of this code, but I
feel even less comfortable having a board crash on boot and I can
attest to there being a dereference of best_parent_hw..

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad


>  drivers/clk/qcom/clk-rcg2.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
> index 2838d4cb2d58..d0a5847f9111 100644
> --- a/drivers/clk/qcom/clk-rcg2.c
> +++ b/drivers/clk/qcom/clk-rcg2.c
> @@ -1264,6 +1264,7 @@ static int clk_gfx3d_determine_rate(struct clk_hw *hw,
>  	if (req->max_rate < parent_req.max_rate)
>  		parent_req.max_rate = req->max_rate;
>  
> +	parent_req.best_parent_hw = req->best_parent_hw;
>  	ret = __clk_determine_rate(req->best_parent_hw, &parent_req);
>  	if (ret)
>  		return ret;
> 
> ---
> base-commit: b775e489bec70895b7ef6b66927886bbac79598f
> change-id: 20260117-db820-fix-gfx3d-e61329023c8a
> 
> Best regards,