linux-kernel - Re: [PATCH v4 3/5] mfd: Add RTL8231 core device

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Message-ID: <76c058318f5c5d984ade4f65bb359e686836b0b4.camel@svanheule.net>
Date:   Sat, 05 Jun 2021 13:07:44 +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>,
        Linus Walleij <linus.walleij@...aro.org>,
        Michael Walle <michael@...le.cc>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Andrew Lunn <andrew@...n.ch>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v4 3/5] mfd: Add RTL8231 core device

On Thu, 2021-06-03 at 13:58 +0300, Andy Shevchenko wrote:
> On Thu, Jun 3, 2021 at 1:01 PM Sander Vanheule <sander@...nheule.net> wrote:
> > +static int rtl8231_reg_read(void *context, unsigned int reg, unsigned int
> > *val)
> > +{
> > +       struct mdio_device *mdio_dev = context;
> > +       int ret;
> > +
> > +       ret = mdiobus_read(mdio_dev->bus, mdio_dev->addr,
> > RTL8231_REAL_REG(reg));
> > +
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       *val = ret & 0xffff;
> > +
> > +       return 0;
> > +}
> > +
> > +static int rtl8231_reg_write(void *context, unsigned int reg, unsigned int
> > val)
> > +{
> > +       struct mdio_device *mdio_dev = context;
> > +
> > +       return mdiobus_write(mdio_dev->bus, mdio_dev->addr,
> > RTL8231_REAL_REG(reg), val);
> > +}
> 
> Hmm... Maybe we can amend regmap-mdio to avoid duplication of the
> above? Something like xlate in gpio-regmap or so?

(+Cc Mark for the regmap discussion)

It turns out that I can't use both devm_regmap_init_mdio and the overrides
regmap_config.reg_read/write. This appears to be in contrast to what the
documentation for these two overrides suggest. devm_regmap_init_mdio provides a
bus for the regmap, which causes the overrides to be ignored in regmap.c

Then I tried to use the paging support provided by regmap, by adding the
following config:
   
      static struct regmap_range_cfg rtl8231_reg_ranges[] = {
             {
                     /* Specify an unused register with an empty mask */
                     .selector_reg = 0x1f,
                     .selector_mask = 0x00,
                     .selector_shift = 0,
                     .range_min = 0x00,
                     .range_max = RTL8231_VREG(RTL8231_REG_COUNT - 1),
                     .window_start = 0x00,
                     .window_len = 0x20,
             },
      };


This also doesn't work, because the used _regmap_bus_reg_read/write don't
resolve register pages. The patch below fixes this, but maybe this missing
functionality is intentional, and I should actually implement
regmap_bus.read/write?

----8<----
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 0d185ec018a5..20b6a2e0d2e3 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1881,6 +1881,15 @@ static int _regmap_bus_reg_write(void *context, unsigned
int reg,
                                 unsigned int val)
 {
        struct regmap *map = context;
+       struct regmap_range_node *range;
+       int ret;
+
+       range = _regmap_range_lookup(map, reg);
+       if (range) {
+               ret = _regmap_select_page(map, &reg, range, 1);
+               if (ret != 0)
+                       return ret;
+       }
 
        return map->bus->reg_write(map->bus_context, reg, val);
 }
@@ -2651,6 +2660,15 @@ static int _regmap_bus_reg_read(void *context, unsigned
int reg,
                                unsigned int *val)
 {
        struct regmap *map = context;
+       struct regmap_range_node *range;
+       int ret;
+
+       range = _regmap_range_lookup(map, reg);
+       if (range) {
+               ret = _regmap_select_page(map, &reg, range, 1);
+               if (ret != 0)
+                       return ret;
+       }
 
        return map->bus->reg_read(map->bus_context, reg, val);
 }

--
Best,
Sander