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

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Message-ID: <fee6fkqhhst6o6rchohp252tzvkfnv7hvro3z7ipv4o3zg5whi@ou6wjcpk74jn>
Date: Tue, 20 Jan 2026 20:25:26 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Brian Masney <bmasney@...hat.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: qcom: gfx3d: add parent to parent request map

On Tue, Jan 20, 2026 at 10:14:32AM -0500, Brian Masney wrote:
> On Mon, Jan 19, 2026 at 09:39:30AM -0600, Bjorn Andersson wrote:
> > On Sat, Jan 17, 2026 at 05:54:47AM +0200, 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@....qualcomm.com>
> > 
> > Why didn't Brian get Cc'ed on this patch? I'd love to have his input.
> 
> Reviewed-by: Brian Masney <bmasney@...hat.com>
> 
> clk_alpha_pll_postdiv_round_rate() previously had this code:
> 
>         return divider_round_rate(hw, rate, prate, table,
>                                   pll->width, CLK_DIVIDER_POWER_OF_TWO);
> 
> divider_round_rate() called divider_round_rate_parent(), which had this
> code that set the best_parent_hw:
> 
> long divider_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
>                                unsigned long rate, unsigned long *prate,
>                                const struct clk_div_table *table,
>                                u8 width, unsigned long flags)
> {
>         struct clk_rate_request req;
>         int ret;
> 
>         clk_hw_init_rate_request(hw, &req, rate);
>         req.best_parent_rate = *prate;
>         req.best_parent_hw = parent;
> 
>         ret = divider_determine_rate(hw, &req, table, width, flags);
>         if (ret)
>                 return ret;
> 
>         *prate = req.best_parent_rate;
> 
>         return req.rate;
> }
> 
> I coverted clk_alpha_pll_postdiv_round_rate() to
> clk_alpha_pll_postdiv_determine_rate(), and that now directly calls
> divider_determine_rate().
> 
> I'll look through the other cases where divider_round_rate_parent() was
> called just to be sure there's no other cases of this.
> 

Thank you, Brian!

> Brian
>