linux-kernel - Re: [PATCH 4/4] clk: qcom: clk-krait: add apq/ipq8064 errata workaround

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Date:   Fri, 29 Apr 2022 18:13:34 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        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 4/4] clk: qcom: clk-krait: add apq/ipq8064 errata workaround

On Fri, 29 Apr 2022 at 18:11, Ansuel Smith <ansuelsmth@...il.com> wrote:
>
> On Fri, Apr 29, 2022 at 06:00:45PM +0300, Dmitry Baryshkov wrote:
> > On 29/04/2022 15:01, Ansuel Smith wrote:
> > > Add apq/ipq8064 errata workaround where the sec_src clock gating needs to
> > > be disabled during switching. To enable this set disable_sec_src_gating
> > > in the mux struct.
> > >
> > > Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> > > ---
> > >   drivers/clk/qcom/clk-krait.c | 16 ++++++++++++++++
> > >   drivers/clk/qcom/clk-krait.h |  1 +
> > >   drivers/clk/qcom/krait-cc.c  |  1 +
> > >   3 files changed, 18 insertions(+)
> > >
> > > diff --git a/drivers/clk/qcom/clk-krait.c b/drivers/clk/qcom/clk-krait.c
> > > index 6c367ad6506a..4a9b3296c45b 100644
> > > --- a/drivers/clk/qcom/clk-krait.c
> > > +++ b/drivers/clk/qcom/clk-krait.c
> > > @@ -18,13 +18,23 @@
> > >   static DEFINE_SPINLOCK(krait_clock_reg_lock);
> > >   #define LPL_SHIFT 8
> > > +#define SECCLKAGD  BIT(4)
> > > +
> > >   static void __krait_mux_set_sel(struct krait_mux_clk *mux, int sel)
> > >   {
> > >     unsigned long flags;
> > >     u32 regval;
> > >     spin_lock_irqsave(&krait_clock_reg_lock, flags);
> > > +
> > >     regval = krait_get_l2_indirect_reg(mux->offset);
> > > +
> > > +   /* apq/ipq8064 Errata: disable sec_src clock gating during switch. */
> > > +   if (mux->disable_sec_src_gating) {
> > > +           regval |= SECCLKAGD;
> > > +           krait_set_l2_indirect_reg(mux->offset, regval);
> > > +   }
> > > +
> > >     regval &= ~(mux->mask << mux->shift);
> > >     regval |= (sel & mux->mask) << mux->shift;
> > >     if (mux->lpl) {
> > > @@ -33,6 +43,12 @@ static void __krait_mux_set_sel(struct krait_mux_clk *mux, int sel)
> > >     }
> > >     krait_set_l2_indirect_reg(mux->offset, regval);
> > > +   /* apq/ipq8064 Errata: re-enabled sec_src clock gating. */
> > > +   if (mux->disable_sec_src_gating) {
> > > +           regval &= ~SECCLKAGD;
> > > +           krait_set_l2_indirect_reg(mux->offset, regval);
> > > +   }
> > > +
> > >     /* Wait for switch to complete. */
> > >     mb();
> > >     udelay(1);
> > > diff --git a/drivers/clk/qcom/clk-krait.h b/drivers/clk/qcom/clk-krait.h
> > > index 9120bd2f5297..f930538c539e 100644
> > > --- a/drivers/clk/qcom/clk-krait.h
> > > +++ b/drivers/clk/qcom/clk-krait.h
> > > @@ -15,6 +15,7 @@ struct krait_mux_clk {
> > >     u8              safe_sel;
> > >     u8              old_index;
> > >     bool            reparent;
> > > +   bool            disable_sec_src_gating;
> > >     struct clk_hw   hw;
> > >     struct notifier_block   clk_nb;
> > > diff --git a/drivers/clk/qcom/krait-cc.c b/drivers/clk/qcom/krait-cc.c
> > > index 4d4b657d33c3..0f88bf41ec6e 100644
> > > --- a/drivers/clk/qcom/krait-cc.c
> > > +++ b/drivers/clk/qcom/krait-cc.c
> > > @@ -138,6 +138,7 @@ krait_add_sec_mux(struct device *dev, int id, const char *s,
> > >     mux->parent_map = sec_mux_map;
> > >     mux->hw.init = &init;
> > >     mux->safe_sel = 0;
> > > +   mux->disable_sec_src_gating = true;
> >
> > This has to be guarded with the of_compatible checks. Otherwise you'd apply
> > this errata to all Krait CPUs, not only apq/ipq8064.
> >
> > At least this should be limited to krait-cc-v1 with the note that there is
> > no way to distinguish between platforms.
> >
>
> Mhh can't i check the machine compatible directly to limit this to
> apq/ipq8064?

Yes, use of_machine_is_compatible(). Add a comment that you have to do
this because of the lack of soc-specific device compats.

> > >     init.name = kasprintf(GFP_KERNEL, "krait%s_sec_mux", s);
> > >     if (!init.name)
> >
> >
> > --
> > With best wishes
> > Dmitry
>
> --
>         Ansuel



-- 
With best wishes
Dmitry