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From: Rob Herring <firstname.lastname@example.org> To: Doug Anderson <email@example.com> Cc: Manu Gautam <firstname.lastname@example.org>, Kishon Vijay Abraham I <email@example.com>, Stephen Boyd <firstname.lastname@example.org>, LKML <email@example.com>, firstname.lastname@example.org, Vivek Gautam <email@example.com>, Evan Green <firstname.lastname@example.org>, email@example.com, Mark Rutland <firstname.lastname@example.org> Subject: Re: [PATCH v4 6/7] dt-bindings: phy-qcom-usb2: Add support to override tuning values Date: Mon, 9 Apr 2018 15:18:24 -0500 [thread overview] Message-ID: <20180409201824.adsnvqo4vv2waixc@rob-hp-laptop> (raw) In-Reply-To: <CAD=FV=VGtmWTaa_aRG6UVAtCzy3cS8sTZDCqAgRMYeg7U02qTw@mail.gmail.com> On Thu, Mar 29, 2018 at 01:38:23PM -0700, Doug Anderson wrote: > Hi, > > On Thu, Mar 29, 2018 at 4:04 AM, Manu Gautam <email@example.com> wrote: > > To improve eye diagram for PHYs on different boards of same SOC, > > some parameters may need to be changed. Provide device tree > > properties to override these from board specific device tree > > files. While at it, replace "qcom,qusb2-v2-phy" with compatible > > string for USB2 PHY on sdm845 which was earlier added for > > sdm845 only. > > > > Signed-off-by: Manu Gautam <firstname.lastname@example.org> > > --- > > .../devicetree/bindings/phy/qcom-qusb2-phy.txt | 19 ++++++++++++++++++- > > 1 file changed, 18 insertions(+), 1 deletion(-) > > > > diff --git a/Documentation/devicetree/bindings/phy/qcom-qusb2-phy.txt b/Documentation/devicetree/bindings/phy/qcom-qusb2-phy.txt > > index 42c9742..0ed140a 100644 > > --- a/Documentation/devicetree/bindings/phy/qcom-qusb2-phy.txt > > +++ b/Documentation/devicetree/bindings/phy/qcom-qusb2-phy.txt > > @@ -6,7 +6,7 @@ QUSB2 controller supports LS/FS/HS usb connectivity on Qualcomm chipsets. > > Required properties: > > - compatible: compatible list, contains > > "qcom,msm8996-qusb2-phy" for 14nm PHY on msm8996, > > - "qcom,qusb2-v2-phy" for QUSB2 V2 PHY. > > + "qcom,sdm845-qusb2-phy" for 10nm PHY on sdm845. > > > > - reg: offset and length of the PHY register set. > > - #phy-cells: must be 0. > > @@ -27,6 +27,23 @@ Optional properties: > > tuning parameter value for qusb2 phy. > > > > - qcom,tcsr-syscon: Phandle to TCSR syscon register region. > > Just to confirm: the new properties below work just fine on the old > msm8996 PHY too, right? > > > > + - qcom,imp-res-offset-value: It is a 6 bit value that specifies offset to be > > + added to PHY refgen RESCODE via IMP_CTRL1 register. It is a PHY > > + tuning paramter that may vary for different boards of same SOC. > > + - qcom,hstx-trim-value: It is a 4 bit value that specifies tuning for HSTX > > + output current. 0x0 value corresponding to 24mA which is maximum > > + current and 0xf corresponds to lowest current which is 15mA. > > + - qcom,preemphasis-level: It is a 2 bit value that specifies pre-emphasis level. > > + Possible values are: > > + 00: NONE > > + 01: +5% > > + 10: +10% > > + 11: +15% > > The user of the device tree will expect to specify this in decimal, > right? So list the above as 0, 1, 2, 3. ...not 00, 01, 10, 11. > (though below I suggest that specifying 0, 1, 2, 3 is probably not > quite the right way to describe this property). > > > > +- qcom,preemphasis-width: It is a 1 bit value that specifies how long the HSTX > > + pre-emphasis (specified using qcom,preemphasis-level) must be in > > + effect. Possible values are: > > + 0: Full-bit width > > + 1: Half-bit width > > Perhaps just make this a boolean property. If it exists then you get > the non-default case. AKA: if the default is full bit width, then > you'd allow a boolean property "qcom,preemphasis-half-width" to > override. If the default is half bit width then you'd allow > "qcom,preemphasis-full-width" to override. > > > For all the above optional bits, please indicate what the default is > if they aren't specified. If you have to specify a different default > for sdm845 vs. msm8996 then so be it (though it would be nice to avoid > it by changing the default for sdm845 unless that's totally crazy). > > > Overall this looks pretty good to me. Certainly the descriptions are > very understandable and this will make tuning on a per-board / > per-port basis much easier! Thanks! > > > One last overall comment is that ideally we could make the device tree > a little bit more human readable. Right now we'll have a set of > properties that looks like this (numbers made up): > > qcom,imp-res-offset-value = <0x13>; > qcom,hstx-trim-value = <0x7>; > qcom,preemphasis-level = <1>; > qcom,preemphasis-width = <0>; > > > One option to make that more readable would be to change the units, AKA: > > qcom,hstx-trim-ma = <18>; > qcom,preemphasis-percent = <5>; > > ...then the code would translate from these human-readable values to > the real numbers. Yes, we often do that. However, there properties are very specific to this device and making the driver translate back to h/w values doesn't add much. > Another option would be to add a #include to the bindings. I'd defer > to the wisdom of the bindings guys about if this is better or worse > than adding the units, but personally I like it better because: > * You get a compile-time error if you use an unsupported value. > * You don't need to add the code to translate. This is fine for me. Really, I'm fine with it as-is, but #defines make some people happy. Rob
next prev parent reply other threads:[~2018-04-09 20:18 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-29 11:04 [PATCH v4 0/7] phy: qcom: Updates for USB PHYs on SDM845 Manu Gautam 2018-03-29 11:04 ` [PATCH v4 1/7] clk: msm8996-gcc: change halt check for USB/PCIE pipe_clk Manu Gautam 2018-03-29 20:55 ` Doug Anderson 2018-04-05 20:07 ` Stephen Boyd 2018-04-10 6:44 ` Manu Gautam 2018-03-29 11:04 ` [PATCH v4 2/7] phy: qcom-qmp: Enable pipe_clk before PHY initialization Manu Gautam 2018-03-29 17:28 ` Evan Green 2018-03-29 18:44 ` Doug Anderson 2018-03-29 20:54 ` Doug Anderson 2018-04-10 6:36 ` Manu Gautam 2018-04-10 15:05 ` Doug Anderson 2018-04-10 18:32 ` Stephen Boyd 2018-04-11 15:37 ` Manu Gautam 2018-04-12 20:38 ` Stephen Boyd 2018-04-13 7:00 ` Manu Gautam 2018-03-29 11:04 ` [PATCH v4 3/7] phy: qcom-qusb2: Fix crash if nvmem cell not specified Manu Gautam 2018-03-29 11:04 ` [PATCH v4 4/7] dt-bindings: phy-qcom-qmp: Update bindings for sdm845 Manu Gautam 2018-03-29 19:39 ` Doug Anderson 2018-03-29 11:04 ` [PATCH v4 5/7] phy: qcom-qmp: Add QMP V3 USB3 UNI PHY support " Manu Gautam 2018-03-29 11:04 ` [PATCH v4 6/7] dt-bindings: phy-qcom-usb2: Add support to override tuning values Manu Gautam 2018-03-29 20:38 ` Doug Anderson 2018-04-09 20:18 ` Rob Herring [this message] 2018-04-10 7:16 ` Manu Gautam 2018-04-12 20:47 ` Doug Anderson 2018-04-16 1:36 ` Manu Gautam 2018-03-29 11:04 ` [PATCH v4 7/7] phy: qcom-qusb2: Add QUSB2 PHYs support for sdm845 Manu Gautam 2018-03-29 20:38 ` Doug Anderson 2018-04-10 6:55 ` Manu Gautam
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