Re: [RFC PATCH v2] regmap: apply reg_base and reg_downshift for single register ops

[Colin Foster]

Hi Daniel,

On Mon, Jan 30, 2023 at 02:04:57AM +0000, Daniel Golle wrote:
> reg_base and reg_downshift currently don't have any effect if used with
> a regmap_bus or regmap_config which only offers single register
> operations (ie. reg_read, reg_write and optionally reg_update_bits).
> 
> Fix that and take them into account also for regmap_bus with only
> reg_read and read_write operations by applying reg_base and
> reg_downshift in _regmap_bus_reg_write, _regmap_bus_reg_read.
> 
> Also apply reg_base and reg_downshift in _regmap_update_bits, but only
> in case the operation is carried out with a reg_update_bits call
> defined in either regmap_bus or regmap_config.
> 
> Fixes: 0074f3f2b1e43d ("regmap: allow a defined reg_base to be added to every address")
> Fixes: 86fc59ef818beb ("regmap: add configurable downshift for addresses")
> Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
> ---
> I hope that I didn't miss anything there...
> 
> @Colin Please let me know if this breaks anything with your ocelot_spi
> use-case.

I see we're working on similar things! (DSA hardware, that is)

This patch works for me. I don't konw if there's any value in
back-porting it to affected kernels, as ocelot_spi is the only user as
far as I can tell. (wishing I called it something more greppable than
'reg_base')

Tested-by: Colin Foster <colin.foster@xxxxxxxxxxxxxxxx>

> 
>  drivers/base/regmap/regmap.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index d12d669157f24..d2a54eb0efd9b 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -1942,6 +1942,8 @@ static int _regmap_bus_reg_write(void *context, unsigned int reg,
>  {
>  	struct regmap *map = context;
>  
> +	reg += map->reg_base;
> +	reg >>= map->format.reg_downshift;
>  	return map->bus->reg_write(map->bus_context, reg, val);
>  }
>  
> @@ -2840,6 +2842,8 @@ static int _regmap_bus_reg_read(void *context, unsigned int reg,
>  {
>  	struct regmap *map = context;
>  
> +	reg += map->reg_base;
> +	reg >>= map->format.reg_downshift;
>  	return map->bus->reg_read(map->bus_context, reg, val);
>  }
>  
> @@ -3231,6 +3235,8 @@ static int _regmap_update_bits(struct regmap *map, unsigned int reg,
>  		*change = false;
>  
>  	if (regmap_volatile(map, reg) && map->reg_update_bits) {
> +		reg += map->reg_base;
> +		reg >>= map->format.reg_downshift;
>  		ret = map->reg_update_bits(map->bus_context, reg, mask, val);
>  		if (ret == 0 && change)
>  			*change = true;
> -- 
> 2.39.1
>