On Tue, Dec 5, 2017 at 3:09 AM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > Hi Rob, > > On Tue, Dec 5, 2017 at 9:57 AM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: >> On Mon, Dec 4, 2017 at 10:17 PM, Rob Herring <robh@xxxxxxxxxx> wrote: >>> On Mon, Dec 04, 2017 at 10:17:47AM +0100, Geert Uytterhoeven wrote: >>>> On Thu, Nov 30, 2017 at 2:29 PM, Geert Uytterhoeven >>>> <geert+renesas@xxxxxxxxx> wrote: >>>> > Certain EEPROMS have a size that is larger than the number of address >>>> > bytes would allow, and store the MSB of the address in bit 3 of the >>>> > instruction byte. >>>> > >>>> > This can be described in platform data using EE_INSTR_BIT3_IS_ADDR, or >>>> > in DT using the obsolete legacy "at25,addr-mode" property. >>>> > But currently there exists no non-deprecated way to describe this in DT. >>>> > >>>> > Hence extend the existing "address-width" DT property to allow >>>> > specifying 9, 17, or 25 address bits, and enable support for that in the >>>> > driver. >>>> > >>>> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> >>>> > --- >>>> > EEPROMs using 9 address bits are common (e.g. M95040, 25AA040/25LC040). >>>> > Do EEPROMs using 17 or 25 address bits, as mentioned in >>>> > include/linux/spi/eeprom.h, really exist? >>>> > Or should we just limit it to a single odd value (9 bits)? >>>> >>>> At least for the real Atmel parts, only the AT25040 part uses odd (8 + >>>> 1 bit) addressing. >>> >>> Seems like we should have a specific compatible for it. >> >> Possibly. But currently all configuration is done through DT properties, not >> through matching on compatible values. > > Adding compatible values for all known/used parts could quickly become a > large table. > E.g. Atmel/Microchip has 3 variants of 512-byte EEPROMs: AT25040B, > 25LC040A, and 25AA040A. The former uses an 8-byte pagesize, while the > latter parts use 16-byte pagesizes. > Not to mention "compatible" parts from other manufacturers, and all other > supported size. > > Currently all of this is configured through the "pagesize", "size", and > "address-width" DT properties, with matching on generic "atmel,at25". I wasn't suggesting throwing out all these. Just add a compatible for the one oddball 9-bit part. But I'm fine adding address-width=9 too. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
