Re: [RFT PATCH] hwmon: (spd5118) Add support for Renesas/ITD SPD5118 hub controllers

[Guenter Roeck]

Hi Armin,

On 6/16/24 11:09, Armin Wolf wrote:
> Am 14.06.24 um 20:59 schrieb Guenter Roeck:
>
> > The SPD5118 specification says, in its documentation of the page bits
> > in the MR11 register:
> >
> > "
> > This register only applies to non-volatile memory (1024) Bytes) access of
> > SPD5 Hub device.
> > For volatile memory access, this register must be programmed to '000'.
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > "
> >
> > Renesas/ITD SPD5118 hub controllers take this literally and disable access
> > to volatile memory if the page selected in MR11 is != 0. Since the BIOS or
> > ROMMON will access the non-volatile memory and likely select a page != 0,
> > this means that the driver will not instantiate since it can not identify
> > the chip. Even if the driver instantiates, access to volatile registers
> > is blocked after a nvram read operation which selects a page other than 0.
> >
> > To solve the problem, add initialization code to select page 0 during
> > probe. Before doing that, use basic validation to ensure that this is
> > really a SPD5118 device and not some random EEPROM. Explicitly select
> > page 0 when accessing the volatile register space, and protect volatile
> > register access against nvmem access using the device mutex.
>
> Hi,
>
> maybe we can use struct regmap_range_cfg so the paged register accesses are being
> done by the regmap code itself?

In theory that might work, but regmap does not permit a selector register to
be part of another range. The first range would be the non-volatile registers,
and the selector register is part of that for all ranges.

I tried the following ranges configuration.

static const struct regmap_range_cfg spd5118_regmap_range_cfg[] = {
        {
        .selector_reg     = SPD5118_REG_I2C_LEGACY_MODE,
        .selector_mask    = SPD5118_LEGACY_PAGE_MASK,
        .selector_shift   = 0,
        .window_start     = 0,
        .window_len       = SPD5118_PAGE_SIZE,
        .range_min        = 0,
        .range_max        = SPD5118_PAGE_SIZE - 1,
        },
        {
        .selector_reg     = SPD5118_REG_I2C_LEGACY_MODE,
        .selector_mask    = SPD5118_LEGACY_PAGE_MASK,
        .selector_shift   = 0,
        .window_start     = SPD5118_PAGE_SIZE,
        .window_len       = SPD5118_PAGE_SIZE,
        .range_min        = SPD5118_PAGE_SIZE,
        .range_max        = 9 * SPD5118_PAGE_SIZE - 1,
        },
};

This results in

spd5118 0-0050: Range 0: selector for 1 in window
spd5118 0-0050: error -EINVAL: regmap init failed

If you have an idea how to configure the ranges differently,
please let me know.

Thanks,
Guenter