Re: [PATCH 6/6] clk: qcom: Fix APSS PLL and RCG Configuration

[Devi Priya <quic_devipriy@xxxxxxxxxxx>]

Thanks for taking time to review the patch!

On 1/13/2023 9:47 PM, Robert Marko wrote:
> On 13. 01. 2023. 16:20, Konrad Dybcio wrote:
> > On 13.01.2023 15:36, devi priya wrote:
> > > Included CLK_IS_CRITICAL flag which helps to properly enable
> > > the APSS PLL during bootup.
> > Please describe the issue and not only the user-visible impact it
> > makes. Does the PLL get shut down by clk_ignore_unused? Maybe you
> > would be interested in the sync_state changes that landed in recent
> > -next that may solve it for you?
> >
> > I don't think it should be always-on, as you have an alternate source
> > for low power modes, adding CLK_IS_CRITICAL will keep the PLL enabled
> > even if you're not using it.
>
> I have the same opinion, as this is working fine on IPQ6018 and IPQ8074
> and I have not experienced any issues with it.
Sure, will drop the critical flag
> > > clk_rcg2_ops should be used for APSS clock RCG, as other ops
> > > will not configure the RCG register
> > RCG register meaning RCG register*s*, meaning in this case M/N/D
> > which would be required for proper rate setting and not only input
> > switching (which arguably doesn't seem to be of much concern on a
> > single-parent clock)? This all is not obvious..
> Same question from me as well, why do you need clk_rcg2_ops with
> a dummy frequency table since this is just a mux using RCG2 control
> bits?
>
> Regards,
> Robert
> >
The RCGR is used for source selection whereas the rate setting is done 
by configuring the PLL. The source is configured in the RCGR using the 
source entry (P_APSS_PLL_EARLY) added to the frequency table.

> > Konrad
> > > Co-developed-by: Praveenkumar I <quic_ipkumar@xxxxxxxxxxx>
> > > Signed-off-by: Praveenkumar I <quic_ipkumar@xxxxxxxxxxx>
> > > Signed-off-by: devi priya <quic_devipriy@xxxxxxxxxxx>
> > > ---
> > >   drivers/clk/qcom/apss-ipq-pll.c | 1 +
> > >   drivers/clk/qcom/apss-ipq6018.c | 8 +++++++-
> > >   2 files changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clk/qcom/apss-ipq-pll.c 
> > > b/drivers/clk/qcom/apss-ipq-pll.c
> > > index dd0c01bf5a98..75486a124fcd 100644
> > > --- a/drivers/clk/qcom/apss-ipq-pll.c
> > > +++ b/drivers/clk/qcom/apss-ipq-pll.c
> > > @@ -33,6 +33,7 @@ static struct clk_alpha_pll ipq_pll = {
> > >               },
> > >               .num_parents = 1,
> > >               .ops = &clk_alpha_pll_huayra_ops,
> > > +            .flags = CLK_IS_CRITICAL,
> > >           },
> > >       },
> > >   };
> > > diff --git a/drivers/clk/qcom/apss-ipq6018.c 
> > > b/drivers/clk/qcom/apss-ipq6018.c
> > > index f2f502e2d5a4..0d0e7196a4dc 100644
> > > --- a/drivers/clk/qcom/apss-ipq6018.c
> > > +++ b/drivers/clk/qcom/apss-ipq6018.c
> > > @@ -33,15 +33,21 @@ static const struct parent_map 
> > > parents_apcs_alias0_clk_src_map[] = {
> > >       { P_APSS_PLL_EARLY, 5 },
> > >   };
> > > +static const struct freq_tbl ftbl_apcs_alias0_clk_src[] = {
> > > +    { .src = P_APSS_PLL_EARLY, .pre_div = 1 },
> > > +    { }
> > > +};
> > > +
> > >   static struct clk_rcg2 apcs_alias0_clk_src = {
> > >       .cmd_rcgr = 0x0050,
> > > +    .freq_tbl = ftbl_apcs_alias0_clk_src,
> > >       .hid_width = 5,
> > >       .parent_map = parents_apcs_alias0_clk_src_map,
> > >       .clkr.hw.init = &(struct clk_init_data){
> > >           .name = "apcs_alias0_clk_src",
> > >           .parent_data = parents_apcs_alias0_clk_src,
> > >           .num_parents = ARRAY_SIZE(parents_apcs_alias0_clk_src),
> > > -        .ops = &clk_rcg2_mux_closest_ops,
> > > +        .ops = &clk_rcg2_ops,
> > >           .flags = CLK_SET_RATE_PARENT,
> > >       },
> > >   };
Best Regards,
Devi Priya