linux-kernel - Re: [PATCH v3 4/6] mfd: Add RTL8231 core device

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Message-ID: <cb8593ab7a70528528bae3de45e33fae68a9ec1c.camel@svanheule.net>
Date:   Mon, 24 May 2021 10:23:35 +0200
From:   Sander Vanheule <sander@...nheule.net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 4/6] mfd: Add RTL8231 core device

Hi Andy,

On Mon, 2021-05-24 at 11:02 +0300, Andy Shevchenko wrote:
> On Mon, May 24, 2021 at 1:34 AM Sander Vanheule <sander@...nheule.net> wrote:
> > 
> > The RTL8231 is implemented as an MDIO device, and provides a regmap
> > interface for register access by the core and child devices.
> > 
> > The chip can also be a device on an SMI bus, an I2C-like bus by Realtek.
> > Since kernel support for SMI is limited, and no real-world SMI
> > implementations have been encountered for this device, this is currently
> > unimplemented. The use of the regmap interface should make any future
> > support relatively straightforward.
> > 
> > After reset, all pins are muxed to GPIO inputs before the pin drivers
> > are enabled. This is done to prevent accidental system resets, when a
> > pin is connected to the parent SoC's reset line.
> 
> ...
> 
> > [missing MDIO_BUS dependency, provided via REGMAP_MDIO]
> > Reported-by: kernel test robot <lkp@...el.com>
> 
> What does this fix? Shouldn't it have a Fixes tag? (Yes, I know that
> you answered in the other email, but here is a hint: before settling
> these kinds of things do not send a new version. Instead of speeding
> up the review you are closer to the chance to have this been not
> applied for v5.14 at all)
> 

I'll drop this from the commit message, if this isn't appropriate without a
Fixes-tag (which I can't provide anyway).


> ...
> 
> > +       /* SOFT_RESET bit self-clears when done */
> > +       regmap_update_bits(map, RTL8231_REG_PIN_HI_CFG,
> > +               RTL8231_PIN_HI_CFG_SOFT_RESET,
> > RTL8231_PIN_HI_CFG_SOFT_RESET);
> 
> > +       usleep_range(1000, 10000);
> 
> It's strange to see this big range of minimum and maximum sleep.
> Usually the ratio should not be bigger than ~3-4 between the values.

I could also change this from a usleep to a polling loop that checks (with a
loop limit) if the reset bit has self-cleared already. 

The datasheet that I have doesn't mention how fast it should self-clear. So I
checked, and it appears to be done after one loop iteration already. So,
certainly faster than the current usleep.

Would a polling loop (with maybe like max. 10 iterations) be a good alternative
for you?

> 
> ...
> 
> > +       regmap_write(map, RTL8231_REG_PIN_MODE0, 0xffff);
> > +       regmap_write(map, RTL8231_REG_GPIO_DIR0, 0xffff);
> > +       regmap_write(map, RTL8231_REG_PIN_MODE1, 0xffff);
> > +       regmap_write(map, RTL8231_REG_GPIO_DIR1, 0xffff);
> 
> GENMASK() ?
> Actually it seems it deserves a special definition like
> 
> ..._ALL_PIN_MASK  GENMASK(15, 0)

Ok, I'll add the extra macro to clarify the intent of the values.


Best,
Sander