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Message-ID: <CACRpkdYe-tW2K2eOQa+FYb-ZXzrA95+pPc6kkLB8ZJLAT8G_eA@mail.gmail.com>
Date: Tue, 9 Nov 2021 02:01:37 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Emil Renner Berthing <kernel@...il.dk>,
linux-riscv <linux-riscv@...ts.infradead.org>,
devicetree <devicetree@...r.kernel.org>,
linux-clk <linux-clk@...r.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
"open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Rob Herring <robh+dt@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Marc Zyngier <maz@...nel.org>,
Philipp Zabel <p.zabel@...gutronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Jiri Slaby <jirislaby@...nel.org>,
Maximilian Luz <luzmaximilian@...il.com>,
Sagar Kadam <sagar.kadam@...ive.com>,
Drew Fustini <drew@...gleboard.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Michael Zhu <michael.zhu@...rfivetech.com>,
Fu Wei <tekkamanninja@...il.com>,
Anup Patel <anup.patel@....com>,
Atish Patra <atish.patra@....com>,
Matteo Croce <mcroce@...rosoft.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Huan Feng <huan.feng@...rfivetech.com>
Subject: Re: [PATCH v3 12/16] pinctrl: starfive: Add pinctrl driver for
StarFive SoCs
On Tue, Nov 2, 2021 at 9:08 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
(...)
> > On Tue, Nov 2, 2021 at 6:50 PM Emil Renner Berthing <kernel@...il.dk> wrote:
>
> ...
>
> > > +static int starfive_pinconf_group_set(struct pinctrl_dev *pctldev,
> > > + unsigned int gsel,
> > > + unsigned long *configs,
> > > + unsigned int num_configs)
> > > +{
> > > + struct starfive_pinctrl *sfp = pinctrl_dev_get_drvdata(pctldev);
> > > + const struct group_desc *group;
> > > + u16 mask, value;
> > > + int i;
> > > +
> > > + group = pinctrl_generic_get_group(pctldev, gsel);
> > > + if (!group)
> > > + return -EINVAL;
> > > +
> > > + mask = 0;
> > > + value = 0;
> > > + for (i = 0; i < num_configs; i++) {
> > > + int param = pinconf_to_config_param(configs[i]);
> > > + u32 arg = pinconf_to_config_argument(configs[i]);
> > > +
> > > + switch (param) {
> > > + case PIN_CONFIG_BIAS_DISABLE:
> > > + mask |= PAD_BIAS_MASK;
> > > + value = (value & ~PAD_BIAS_MASK) | PAD_BIAS_DISABLE;
> > > + break;
> > > + case PIN_CONFIG_BIAS_PULL_DOWN:
> > > + if (arg == 0)
> > > + return -ENOTSUPP;
> > > + mask |= PAD_BIAS_MASK;
> > > + value = (value & ~PAD_BIAS_MASK) | PAD_BIAS_PULL_DOWN;
> > > + break;
> > > + case PIN_CONFIG_BIAS_PULL_UP:
> > > + if (arg == 0)
> > > + return -ENOTSUPP;
> > > + mask |= PAD_BIAS_MASK;
> > > + value = value & ~PAD_BIAS_MASK;
> > > + break;
> > > + case PIN_CONFIG_DRIVE_STRENGTH:
> > > + mask |= PAD_DRIVE_STRENGTH_MASK;
> > > + value = (value & ~PAD_DRIVE_STRENGTH_MASK) |
> > > + starfive_drive_strength_from_max_mA(arg);
> > > + break;
> > > + case PIN_CONFIG_INPUT_ENABLE:
> > > + mask |= PAD_INPUT_ENABLE;
> > > + if (arg)
> > > + value |= PAD_INPUT_ENABLE;
> > > + else
> > > + value &= ~PAD_INPUT_ENABLE;
> > > + break;
> > > + case PIN_CONFIG_INPUT_SCHMITT_ENABLE:
> > > + mask |= PAD_INPUT_SCHMITT_ENABLE;
> > > + if (arg)
> > > + value |= PAD_INPUT_SCHMITT_ENABLE;
> > > + else
> > > + value &= ~PAD_INPUT_SCHMITT_ENABLE;
> > > + break;
> > > + case PIN_CONFIG_SLEW_RATE:
> > > + mask |= PAD_SLEW_RATE_MASK;
> > > + value = (value & ~PAD_SLEW_RATE_MASK) |
> > > + ((arg << PAD_SLEW_RATE_POS) & PAD_SLEW_RATE_MASK);
> > > + break;
> > > + case PIN_CONFIG_STARFIVE_STRONG_PULL_UP:
> > > + if (arg) {
> > > + mask |= PAD_BIAS_MASK;
> > > + value = (value & ~PAD_BIAS_MASK) |
> > > + PAD_BIAS_STRONG_PULL_UP;
> > > + } else {
> > > + mask |= PAD_BIAS_STRONG_PULL_UP;
> > > + value = value & ~PAD_BIAS_STRONG_PULL_UP;
> > > + }
> > > + break;
> > > + default:
> > > + return -ENOTSUPP;
> > > + }
> > > + }
> > > +
> > > + for (i = 0; i < group->num_pins; i++)
> > > + starfive_padctl_rmw(sfp, group->pins[i], mask, value);
> > > +
> > > + return 0;
> > > +}
>
> Linus any comments on this code (sorry if I missed your reply)? The
> idea behind above is to skip all settings from the same category and
> apply only the last one, e.g. if we have "bias set to X", ..., "bias
> disable", ..., "bias set to Y", the hardware will see only the last
> operation, i.e. "bias set to Y". I think it may not be the best
> approach (theoretically?) since the hardware definitely may behave
> differently on the other side in case of such series of the
> configurations (yes, I have seen some interesting implementations of
> the touchpad / touchscreen GPIOs that may be affected).
That sounds weird. I think we need to look at how other drivers
deal with this.
To me it seems more natural that
starfive_padctl_rmw(sfp, group->pins[i], mask, value);
would get called at the end of each iteration of the
for (i = 0; i < num_configs; i++) loop.
Yours,
Linus Walleij
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