linux-kernel - Re: [dragonboard] [PATCH 1/1] dts: qcom: db820c: Add gpio-line-names property

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Date:   Mon, 16 Apr 2018 15:33:06 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Todor Tomov <todor.tomov@...aro.org>
Cc:     linus.walleij@...aro.org, andy.gross@...aro.org,
        david.brown@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        catalin.marinas@....com, bjorn.andersson@...aro.org,
        will.deacon@....com, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dragonboard@...ts.96boards.org, linux-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [dragonboard] [PATCH 1/1] dts: qcom: db820c: Add gpio-line-names
 property

Hi Todor,

On Mon, Apr 16, 2018 at 11:48:59AM +0300, Todor Tomov wrote:
> Hi Mani,
> 
> Thank you for the patch.
> 
> On 14.04.2018 06:18, Manivannan Sadhasivam wrote:
> > Add gpio-line-names property for Dragonboard820c based on APQ8096 SoC.
> > There are 4 gpio-controllers present on this board, including the
> > APQ8096 SoC, PM8994 (GPIO and MPP) and PMI8994 (GPIO).
> > 
> > Lines names are derived from 96Boards CE Specification 1.0, Appendix
> > "Expansion Connector Signal Description". Line names for PMI8994 MPP
> > pins are not added due to the absence of the gpio-controller support.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi | 240 +++++++++++++++++++++++++++
> >  1 file changed, 240 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi b/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
> > index 1c8f1b86472d..1c1deef031c6 100644
> > --- a/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
> > @@ -19,6 +19,34 @@
> >  #include <dt-bindings/input/input.h>
> >  #include <dt-bindings/gpio/gpio.h>
> >  
> > +/*
> > + * GPIO name legend: proper name = the GPIO line is used as GPIO
> > + *         NC      = not connected (pin out but not routed from the chip to
> > + *                   anything the board)
> > + *         "[PER]" = pin is muxed for [peripheral] (not GPIO)
> > + *         LSEC    = Low Speed External Connector
> > + *         HSEC    = High Speed External Connector
> > + *         P HSEC  = Primary High Speed External Connector
> > + *         S HSEC  = Secondary High Speed External Connector
> > + *         J14     = Camera Connector
> > + *         TP      = Test Points
> > + *
> > + * Line names are taken from the schematic "DragonBoard 820c",
> > + * drawing no: LM25-P2751-1
> > + *
> > + * For the lines routed to the external connectors the
> > + * lines are named after the 96Boards CE Specification 1.0,
> > + * Appendix "Expansion Connector Signal Description".
> > + *
> > + * When the 96Board naming of a line and the schematic name of
> > + * the same line are in conflict, the 96Board specification
> > + * takes precedence, which means that the external UART on the
> > + * LSEC is named UART0 while the schematic and SoC names this
> > + * UART3. This is only for the informational lines i.e. "[FOO]",
> 
> It seems to me that this can lead to some confusion for cases when
> some schematic names have 96board names and others don't. (An
> example below.) However I don't really see any better way to do
> it. I'm wondering whether adding the schematic name in
> the comment (for gpios which are named with 96board names)
> can help a little. What do you think? Or any other idea?
>

Specifying the schematic names in comments is a good idea!

Linus: Do you have any suggestion here?

> > + * the GPIO named lines "GPIO-A" thru "GPIO-L" are the only
> > + * ones actually used for GPIO.
> > + */
> > +
> >  / {
> >  	aliases {
> >  		serial0 = &blsp2_uart1;
> > @@ -90,6 +118,218 @@
> >  			status = "okay";
> >  		};
> >  
> > +		pinctrl@...0000 {
> > +			gpio-line-names =
> > +				"[SPI0_DOUT]", /* GPIO_0, LSEC pin 14 */
> > +				"[SPI0_DIN]", /* GPIO_1, LSEC pin 10 */
> > +				"[SPI0_CS]", /* GPIO_2, LSEC pin 12 */
> > +				"[SPI0_SCLK]", /* GPIO_3, LSEC pin 8 */
> > +				"[UART1_TxD]", /* GPIO_4, LSEC pin 11 */
> > +				"[UART1_RxD]", /* GPIO_5, LSEC pin 13 */
> > +				"[I2C1_SDA]", /* GPIO_6, LSEC pin 21 */
> > +				"[I2C1_SCL]", /* GPIO_7, LSEC pin 19 */
> > +				"GPIO-H", /* GPIO_8, LSEC pin 30 */
> > +				"TP93", /* GPIO_9 */
> > +				"GPIO-G", /* GPIO_10, LSEC pin 29 */
> > +				"[MDP_VSYNC_S]", /* GPIO_11, P HSEC pin 55 */
> > +				"NC", /* GPIO_12 */
> > +				"[CSI0_MCLK]", /* GPIO_13, P HSEC pin 15 */
> > +				"[CAM_MCLK1]", /* GPIO_14, J14 pin 11 */
> > +				"[CSI1_MCLK]", /* GPIO_15, P HSEC pin 17 */
> 
> This could be a little misleading.
> 96Board name / schametic name:
> CSI0_MCLK / CAM_MCLK0
> --------- / CAM_MCLK1
> CSI1_MCLK / CAM_MCLK2
>

Agree. Will add the schematic names (CAM_MCLKn) in comments.

Thanks,
Mani
 
> <snip>
> 
> -- 
> Best regards,
> Todor Tomov