Copy Andy & Frank, > -----Original Message----- > From: Michal Vokáč [mailto:michal.vokac@xxxxxxxxx] > Sent: Tuesday, June 12, 2018 11:10 PM > To: linux-gpio@xxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; Shawn Guo > <shawnguo@xxxxxxxxxx>; Sascha Hauer <kernel@xxxxxxxxxxxxxx>; Fabio > Estevam <fabio.estevam@xxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; > devicetree@xxxxxxxxxxxxxxx; A.s. Dong <aisheng.dong@xxxxxxx>; Fabio > Estevam <festevam@xxxxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; > Stefan Agner <stefan@xxxxxxxx>; Pengutronix Kernel Team > <kernel@xxxxxxxxxxxxxx>; Linus Walleij <linus.walleij@xxxxxxxxxx>; linux- > kernel@xxxxxxxxxxxxxxx > Subject: Re: [RFC] Configure i.MX6 RGMII pad group control registers from > device tree > > On 11.6.2018 14:36, Michal Vokáč wrote: > > Ahoj, > > > > To configure individual pad's characteristics on i.MX6 SoC a fsl,pins > > = <PIN_FUNC_ID CONFIG> property can be used. Is there any convenient > > way to configure the pad group control registers? > > > > The issue is that some bits (DDR_SEL and ODT) in the individual RGMII > > pad control registers are read-only. To tweak those parameters (signal > > voltage and termination resistors) one need to write to the pad group > > control registers for the whole RGMII pad group. Namely > > IOMUXC_SW_PAD_CTL_GRP_DDR_TYPE_RGMII and > > IOMUXC_SW_PAD_CTL_GRP_RGMII_TERM. The group registers in general > are not accessible from the list in arch/arm/boot/dts/imx6dl-pinfunc.h. > > > > I could not find any other way to change the group registers than > > hacking-in some lines into the imx6q_init_machine(void) function in > > arch/arm/mach-imx/mach-imx6q.c source. As I work towards upstreaming > > my board this should be done from my device tree or solved in some > universal way. > > > > Any hints will be much appreciated. > > Michal > > I figured out this is more "pinctrl-imx.c" than "device-tree" related so I am > kindly adding maintainers of that file in hope somebody will shed some light > to it. > > I am diving deeper into the code and it seems there really is no generic > option to set the i.MX6 pad group control registers from device tree. > Or am I looking at the problem from a wrong angle? > Yes, there's a few special pad group ctrl registers (e.g. DRAM and RGMII for mx6q) which are not added In the pinctrl driver support. > How should we deal with boards that need to configure some pad > characteristics available only through the pad group control registers? > Andy, How do we handle it internally? > I also raised this question at the NXP community forum [1] and get quite > unsatisfying answer so far. I would love to find/implement a proper and > universal solution. > There're probably two ways to do it: 1) handle it in fec driver by parsing a specific property 2) Add a new pad group into pinctrl driver support e.g. MX6Q_PAD_CTL_GRP_RGMII_TERM MX6Q_PAD_CTL_GRP_DDR_TYPE_RGMII I may prefer to 2). Regards Dong Aisheng > Thanks in advance for your time, > Michal > > [1] > https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fco > mmunity.nxp.com%2Fthread%2F477464&data=02%7C01%7Caisheng.dong%4 > 0nxp.com%7Ca3e5463eb06a47f1121008d5d0768a04%7C686ea1d3bc2b4c6fa9 > 2cd99c5c301635%7C0%7C1%7C636644129914162495&sdata=xqtBS8uX%2BSzq > 5m6tbNaLzCkB7ezgHSnyu9GQ3K13cW8%3D&reserved=0 ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
