[PATCH 2/2] [POWERPC] Describe memory-mapped RAM&ROM chips of bindings

[Laurent Pinchart]

On Wednesday 26 March 2008 15:52, Segher Boessenkool wrote:
> > +    Dedicated RAM and ROM chips are often used as storage for 
> > temporary or
> > +    permanent data in embedded devices. Possible usage include 
> > non-volatile
> > +    storage in battery-backed SRAM, semi-permanent storage in 
> > dedicated SRAM
> > +    to preserve data accross reboots and firmware storage in 
> > dedicated ROM.
> > +
> > +     - compatible : should contain the specific model of RAM/ROM 
> > chip(s)
> > +       used, if known, followed by either "physmap-ram" or 
> > "physmap-rom"
> > +     - reg : Address range of the RAM/ROM chip
> > +     - bank-width : Width (in bytes) of the RAM/ROM bank. Equal to the
> > +       device width times the number of interleaved chips.
> > +     - device-width : (optional) Width of a single RAM/ROM chip. If
> > +       omitted, assumed to be equal to 'bank-width'.
> 
> Maybe I'm rehashing some old discussion here, if so, sorry; but why
> do you have bank-width and device-width here?  What useful information
> does it provide?  If this is about saying what the preferred (or only
> possible) access width is, better names are in order.

device-width isn't used so we can get rid of it. bank-width is used by the 
map_ram driver for erase operations (mapram_erase in 
drivers/mtd/chips/map_ram.c). To be honest I'm not sure why it uses such an 
inefficient approach instead of memsetting the whole area.

-- 
Laurent Pinchart
CSE Semaphore Belgium

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