linux-kernel - Re: [PATCH v3 2/3] phy: qcom-qmp-combo: Add config for SM6350

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Message-Id: <CPZJ4F39LES0.ANG4EP8EUFI7@otso>
Date:   Mon, 23 Jan 2023 12:22:32 +0100
From:   "Luca Weiss" <luca.weiss@...rphone.com>
To:     "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>,
        "Johan Hovold" <johan@...nel.org>
Cc:     "Vinod Koul" <vkoul@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <~postmarketos/upstreaming@...ts.sr.ht>,
        <phone-devel@...r.kernel.org>, "Andy Gross" <agross@...nel.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        "Konrad Dybcio" <konrad.dybcio@...aro.org>,
        "Kishon Vijay Abraham I" <kishon@...nel.org>,
        <linux-phy@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] phy: qcom-qmp-combo: Add config for SM6350

On Mon Jan 23, 2023 at 12:15 PM CET, Dmitry Baryshkov wrote:
> On 23/01/2023 11:43, Johan Hovold wrote:
> > On Fri, Jan 20, 2023 at 03:13:46PM +0100, Luca Weiss wrote:
> >> On Fri Jan 13, 2023 at 2:01 PM CET, Dmitry Baryshkov wrote:
> >>> On Fri, 13 Jan 2023 at 14:44, Luca Weiss <luca.weiss@...rphone.com> wrote:
> >>>>
> >>>> Hi Dmitry,
> >>>>
> >>>> On Thu Jan 12, 2023 at 8:33 PM CET, Dmitry Baryshkov wrote:
> >>>>> On 12/01/2023 19:50, Vinod Koul wrote:
> >>>>>> On 28-12-22, 15:17, Johan Hovold wrote:
> >>>>>>> Luca, Vinod,
> >>>>>>>
> >>>>>>> On Wed, Nov 30, 2022 at 09:14:28AM +0100, Luca Weiss wrote:
> >>>>>>>> Add the tables and config for the combo phy found on SM6350.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> >>>>>>>> ---
> >>>>>>>> Changes since v2:
> >>>>>>>> * Drop dp_txa/dp_txb changes, not required
> >>>>>>>> * Fix dp_dp_phy offset
> >>>>>>>>
> >>>>>>>>    drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 126 ++++++++++++++++++++++
> >>>>>>>>    1 file changed, 126 insertions(+)
> >>>>>>>>
> >>>>>>>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> >>>>>>>> index 77052c66cf70..6ac0c68269dc 100644
> >>>>>>>> --- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> >>>>>>>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> >>>>>>>
> >>>>>>>> @@ -975,6 +1039,19 @@ static const char * const sc7180_usb3phy_reset_l[] = {
> >>>>>>>>            "phy",
> >>>>>>>>    };
> >>>>>>>>
> >>>>>>>> +static const struct qmp_combo_offsets qmp_combo_offsets_v3 = {
> >>>>>>>> + .com            = 0x0000,
> >>>>>>>> + .txa            = 0x1200,
> >>>>>>>> + .rxa            = 0x1400,
> >>>>>>>> + .txb            = 0x1600,
> >>>>>>>> + .rxb            = 0x1800,
> >>>>>>>> + .usb3_serdes    = 0x1000,
> >>>>>>>> + .usb3_pcs_misc  = 0x1a00,
> >>>>>>>> + .usb3_pcs       = 0x1c00,
> >>>>>>>> + .dp_serdes      = 0x1000,
> >>>>>>>
> >>>>>>> I would have expected this to be 0x2000 as that's what the older
> >>>>>>> platforms have been using for the dp serdes table so far. Without access
> >>>>>>> to any documentation it's hard to tell whether everyone's just been
> >>>>>>> cargo-culting all along or if there's actually something there at offset
> >>>>>>> 0x2000.
> >>>>>
> >>>>> usb3_serdes is 0x1000, so dp_serdes equal to 0x1000 is definitely an typo.
> >>>>>
> >>>>> Judging from the downstream dtsi, the DP PHY starts at offset 0x2000. So
> >>>>> dp_serdes is equal to 0x2000, dp_phy = 0x2a00, ln_tx1 = 0x2200, ln_tx2 =
> >>>>> 0x2600.
> >>>>
> >>>> Can you share how you got to the 0x2000 offset? You can see my
> >>>> (potentially wrong) reasoning for 0x1000 a few messages ago[0].
> >>>>
> >>>> The only 0x2000-something I could find now while looking at it again is
> >>>> "#define USB3_DP_PHY_DP_DP_PHY_PD_CTL 0x2a18" which becomes
> >>>> USB3_DP_DP_PHY_PD_CTL in the driver but this is seemingly not used at
> >>>> all in my msm-4.19 tree.
> >>>
> >>> Quite simple: see [1]. DP_PLL is at +0x2000
> >>>
> >>> [1] https://android.googlesource.com/kernel/msm-extra/devicetree/+/refs/heads/android-msm-bramble-4.19-android11-qpr1/qcom/lagoon-sde-pll.dtsi#27
> >>
> >> I still disagree from what I see.
> >>
> >> E.g. this part of the dp_serdes init table in mainline:
> >>
> >> static const struct qmp_phy_init_tbl qmp_v3_dp_serdes_tbl_rbr[] = {
> >> 	QMP_PHY_INIT_CFG(QSERDES_V3_COM_HSCLK_SEL, 0x0c),
> >>
> >> With this one:
> >> #define QSERDES_V3_COM_HSCLK_SEL                     0x13c
> >>
> >> To write this config qmp->dp_serdes gets used which is set at:
> >> 	qmp->dp_serdes = base + offs->dp_serdes;
> >>
> >> So if offs->dp_serdes is 0x2000, this write will go to 0x213c.
> >>
> >> If we go back to msm-4.19 downstream the equivalent define is
> >> #define USB3_DP_QSERDES_COM_HSCLK_SEL				0x113c
>
> There are two SERDES regions. One used by USB part of the PHY (at 
> 0x1000) and another SERDES region used for DP (at 0x2000). As Johan 
> described below, vendor kernel handles the DP regions in the DP driver. 
> Possibly this caused a confusion on your side.

Ack, I think I got it now. I also see the registers used downstream
now, e.g.:

techpack/display/pll/dp_pll_10nm_util.c:#define QSERDES_COM_LOCK_CMP2_MODE0             0x009C

So now .dp_serdes should be 0x2000. Do I need to change anything else
also? I think not?

Regards
Luca

>
> >>
> >> So there we are at offset 0x1000. And this define is used in
> >> qcom,qmp-phy-init-seq which I already went to in detail in a previous
> >> email in this thread.
> > 
> >  From what I've heard, the PHY driver in the vendor kernel only deals
> > with the USB part of the PHY, while some display driver accesses the DP
> > part directly. So the fact that the Qualcomm USB PHY driver init
> > sequences don't seem to use the DP regions (apart from that
> > USB3_DP_PHY_DP_DP_PHY_PD_CTL register) is to be expected.
>
> Correct.
>
> > 
> > IIRC the v3 layout was also used by the SoC for which DP support was
> > first implemented. Presumably, the separate USB and DP regions do exist
> > and you should include them also for SM6350 even if you can't test it
> > currently.
>
> Correct. sdm845 and sc7180 are v3 and they handle DP and USB3 regions 
> separately inside a single Combo driver.
>
> > We'll convert the older platforms over to use the new binding scheme
> > soon and then we'd need this anyway. And if it turns out later that this
> > was all bogus, at least we only need to fix the driver (and not worry
> > about dts backward compatibility as we had to with the old style
> > bindings).
>
> As you mentioned this. Do you have plans to work on this conversion? If 
> not, I'll probably take a look during next development window.
> -- 
> With best wishes
> Dmitry