On Thu, 4 Oct 2018 00:14:15 +0200 Boris Brezillon <boris.brezil...@bootlin.com> wrote:
> On Wed, 3 Oct 2018 23:53:27 +0200 > Ricardo Ribalda Delgado <ricardo.riba...@gmail.com> wrote: > > > Hi Boris > > On Wed, Oct 3, 2018 at 11:27 PM Boris Brezillon > > <boris.brezil...@bootlin.com> wrote: > > > > > > On Wed, 3 Oct 2018 21:38:58 +0200 > > > Ricardo Ribalda Delgado <ricardo.riba...@gmail.com> wrote: > > > > > > > Add documentation for gpio-addr-flash. This binding allow creating > > > > flash devices that are paged using GPIOs. > > > > > > > > Cc: devicet...@vger.kernel.org > > > > Reviewed-by: Rob Herring <r...@kernel.org> > > > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com> > > > > --- > > > > .../bindings/mtd/gpio-addr-flash.txt | 54 +++++++++++++++++++ > > > > 1 file changed, 54 insertions(+) > > > > create mode 100644 > > > > Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt > > > > > > > > diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt > > > > b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt > > > > new file mode 100644 > > > > index 000000000000..5006a26e1753 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt > > > > @@ -0,0 +1,54 @@ > > > > +Memory Mapped flash with some address lines addressed using GPIOs > > > > + > > > > +Handle the case where a flash device is mostly addressed using physical > > > > +line and supplemented by GPIOs. This way you can hook up say a 8MiB > > > > flash > > > > +to a 2MiB memory range and use the GPIOs to select a particular range. > > > > + > > > > + - compatible : "cfi-gpio-addr-flash" > > > > + - reg : Address range of the mtd chip that is memory mapped, this is, > > > > + on the previous example 2MiB. > > > > + - bank-width : Width (in bytes) of the bank. Equal to the > > > > + device width times the number of interleaved chips. > > > > + - gpios: List of GPIO specifiers that will be used to address the > > > > MSBs address > > > > + lines. The order goes from LSB to MSB. > > > > + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip > > > > + is going to be probed. If omitted, assumed to be equal to > > > > "cfi_probe". > > > > > > Looks like other bindings are encoding the probe type in the > > > compatible [1][2], and we should probably follow what's been done by > > > others. > > > > If I understood it right, they are special cases of physmap_of_core.c > > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L242 > > > > The driver that handles the compatible is physmap_of_core.c, and afaik > > multiple drivers with the same > > compatible string is a very bad idea. > > Yes, I know. > > > > > We can convert the driver to something like Versatile or gemini, but > > then we will not support platform devices > > > > btw, the binding that I am used is used by: > > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L91 > > > > Actually, the more I think about it the more I realize this should > somehow be integrated to the physmap core logic. I mean, there's nothing > controller/platform specific in what the gpio-physmap driver does. > > We could basically add the msb_addr_gpios related fields to map_info, > let physmap.c and physmap_of_core.c call > devm_gpiod_get_array_optional() and, based on the returned value, > call simple_map_init() (when the pointer is NULL) or > gpio_addr_map_init() (when the pointer is valid). Or even better, let simple_map_init() call gpio_addr_map_init() when map->addr_gpios != NULL, so that you don't even have to duplicate the selection logic in physmap.c and physmap_of_core.c. > > gpio_addr_map_init() would still be implemented in gpio-addr-flash.c so > that we can still enable/disable support for this feature (providing > dummy wrappers when it's disabled). By doing that, we also keep a single > driver which matches a generic compatible string. We also stay > compatible with .c based board files.
