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

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Message-ID: <aW-b2EmynhZlp0mZ@redhat.com>
Date: Tue, 20 Jan 2026 10:14:32 -0500
From: Brian Masney <bmasney@...hat.com>
To: Bjorn Andersson <andersson@...nel.org>
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 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.

Brian