Re: [alsa-devel] [PATCH 06/17] soundwire: cadence_master: use firmware defaults for frame shape

[Cezary Rojewski]

On 2019-08-06 17:36, Pierre-Louis Bossart wrote:
> On 8/6/19 10:27 AM, Cezary Rojewski wrote:
> > On 2019-08-06 02:55, Pierre-Louis Bossart wrote:
> > > diff --git a/drivers/soundwire/cadence_master.c 
> > > b/drivers/soundwire/cadence_master.c
> > > index 5d9729b4d634..89c55e4bb72c 100644
> > > --- a/drivers/soundwire/cadence_master.c
> > > +++ b/drivers/soundwire/cadence_master.c
> > > @@ -48,6 +48,8 @@
> > > Â #define CDNS_MCP_SSPSTATÂÂÂÂÂÂÂÂÂÂÂ 0xC
> > > Â #define CDNS_MCP_FRAME_SHAPEÂÂÂÂÂÂÂÂÂÂÂ 0x10
> > > Â #define CDNS_MCP_FRAME_SHAPE_INITÂÂÂÂÂÂÂ 0x14
> > > +#define CDNS_MCP_FRAME_SHAPE_COL_MASKÂÂÂÂÂÂÂ GENMASK(2, 0)
> > > +#define CDNS_MCP_FRAME_SHAPE_ROW_OFFSETÂÂÂÂÂÂÂ 3
> > > Â #define CDNS_MCP_CONFIG_UPDATEÂÂÂÂÂÂÂÂÂÂÂ 0x18
> > > Â #define CDNS_MCP_CONFIG_UPDATE_BITÂÂÂÂÂÂÂ BIT(0)
> > > @@ -175,7 +177,6 @@
> > > Â /* Driver defaults */
> > > Â #define CDNS_DEFAULT_CLK_DIVIDERÂÂÂÂÂÂÂ 0
> > > -#define CDNS_DEFAULT_FRAME_SHAPEÂÂÂÂÂÂÂ 0x30
> > > Â #define CDNS_DEFAULT_SSP_INTERVALÂÂÂÂÂÂÂ 0x18
> > > Â #define CDNS_TX_TIMEOUTÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 2000
> > > @@ -901,6 +902,20 @@ int sdw_cdns_pdi_init(struct sdw_cdns *cdns,
> > > Â }
> > > Â EXPORT_SYMBOL(sdw_cdns_pdi_init);
> > > +static u32 cdns_set_initial_frame_shape(int n_rows, int n_cols)
> > > +{
> > > +ÂÂÂ u32 val;
> > > +ÂÂÂ int c;
> > > +ÂÂÂ int r;
> > > +
> > > +ÂÂÂ r = sdw_find_row_index(n_rows);
> > > +ÂÂÂ c = sdw_find_col_index(n_cols) & CDNS_MCP_FRAME_SHAPE_COL_MASK;
> > > +
> > > +ÂÂÂ val = (r << CDNS_MCP_FRAME_SHAPE_ROW_OFFSET) | c;
> > > +
> > > +ÂÂÂ return val;
> > > +}
> > > +
> >
> > Guess this have been said already, but this function could be 
> > simplified - unless you really want to keep explicit variable 
> > declaration. Both "c" and "r" declarations could be merged into single 
> > line while "val" is not needed at all.
> >
> > One more thing - is AND bitwise op really needed for cols explicitly? 
> > We know all col values upfront - these are static and declared in 
> > global table nearby. Static declaration takes care of "initial 
> > range-check". Is another one necessary?
> >
> > Moreover, this is a _get_ and certainly not a _set_ type of function. 
> > I'd even consider renaming it to: "cdns_get_frame_shape" as this is 
> > neither a _set_ nor an explicit initial frame shape setter.
> >
> > It might be even helpful to split two usages:
> >
> > #define sdw_frame_shape(col_idx, row_idx) \
> > ÂÂÂÂÂ((row_idx << CDNS_MCP_FRAME_SHAPE_ROW_OFFSET) | col_idx)
> >
> > u32 cdns_get_frame_shape(u16 rows, u16 cols)
> > {
> > ÂÂÂÂÂu16 c, r;
> >
> > ÂÂÂÂÂr = sdw_find_row_index(rows);
> > ÂÂÂÂÂc = sdw_find_col_index(cols);
> >
> > ÂÂÂÂÂreturn sdw_frame_shape(c, r);
> > }
> >
> > The above may even be simplified into one-liner.
>
> This is a function used once on startup, there is no real need to 
> simplify further. The separate variables help add debug traces as needed 
> and keep the code readable while showing how the values are encoded into 
> a register.

Eh, I've thought it's gonna be exposed to userspace (via uapi) so it can 
be fetched by tests or tools.

In such case - if there is a single usage only - guess function is fine 
as is.