linux-kernel - Re: [PATCH 2/7] clk: qcom: ipq8074: disable USB GDSC-s SW

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Message-ID: <CAOX2RU4B6hqQtJCW3ifXfxd9dMCGE+FygDimGQOP49PRjp_y3g@mail.gmail.com>
Date:   Fri, 6 May 2022 23:54:25 +0200
From:   Robert Marko <robimarko@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        krzysztof.kozlowski+dt@...aro.org,
        Abhishek Sahu <absahu@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-clk@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Devicetree List <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/7] clk: qcom: ipq8074: disable USB GDSC-s SW_COLLAPSE

On Fri, 6 May 2022 at 05:33, Bjorn Andersson <bjorn.andersson@...aro.org> wrote:
>
> On Mon 25 Apr 13:22 CDT 2022, Robert Marko wrote:
>
> > Like in IPQ6018 Qualcomm intentionally disables the SW_COLLAPSE on the USB
> > GDSC-s in the downstream 5.4 kernel.
> >
> > This could potentially be better handled by utilizing the GDSC driver, but
> > I am not familiar with it nor do I have datasheets.
>
> Could you please give it a try before we pick this up?
> Look at e.g. drivers/clk/qcom/gcc-sdm845.c how usb30_prim_gdsc and
> usb30_sec_gdsc are defined, the offsets in specified in .gdscr should be
> the same offsets you give below.
>
> Then you specify an array of struct gdsc *, associating the two gdscs
> you have specified to some identifier (USB30_PRIM_GDSC and
> USB30_SEC_GDSC is used in sdm845) and reference this list as .gdscs and
> num_gdscs in the gcc_ipq8074_desc.
>
> The last part is to tie the USB controllers to the two GDSCs, this is
> done by simply specifying:
>
>         power-domains = <&gcc USB30_PRIM_GDSC>;
>
> and USB30_SEC_GDSC, in the two USB nodes in DeviceTree. SW_COLLAPSE will
> be toggled by the PM state of the USB driver, like it's done on e.g.
> sdm845.

Hi Bjorn, thanks for the tips, it makes more sense now.
The only thing I am not sure about are the feature flags for these GDSCs,
how to figure out which ones are correct as I dont have datasheets and QCA
does not use GDSCs in the downstream kernel?
POLL_CFG_GDSCR will cause the GDSC not to get enabled, while VOTABLE
seems to work.

Regards,
Robert

>
> Regards,
> Bjorn
>
> >
> > Signed-off-by: Robert Marko <robimarko@...il.com>
> > ---
> >  drivers/clk/qcom/gcc-ipq8074.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/clk/qcom/gcc-ipq8074.c b/drivers/clk/qcom/gcc-ipq8074.c
> > index 2ebd1462db78..65249a03a672 100644
> > --- a/drivers/clk/qcom/gcc-ipq8074.c
> > +++ b/drivers/clk/qcom/gcc-ipq8074.c
> > @@ -4806,6 +4806,11 @@ static int gcc_ipq8074_probe(struct platform_device *pdev)
> >       if (IS_ERR(regmap))
> >               return PTR_ERR(regmap);
> >
> > +     /* Disable SW_COLLAPSE for USB0 GDSCR */
> > +     regmap_update_bits(regmap, 0x3e078, BIT(0), 0x0);
> > +     /* Disable SW_COLLAPSE for USB1 GDSCR */
> > +     regmap_update_bits(regmap, 0x3f078, BIT(0), 0x0);
> > +
> >       clk_alpha_pll_configure(&ubi32_pll_main, regmap, &ubi32_pll_config);
> >       clk_alpha_pll_configure(&nss_crypto_pll_main, regmap,
> >                               &nss_crypto_pll_config);
> > --
> > 2.35.1
> >