Messages in this thread | | | Date | Tue, 2 May 2017 09:15:30 -0700 | From | Brian Norris <> | Subject | Re: [PATCH] mtd: nand: gpio: make nCE GPIO optional |
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Hi Christophe, Boris,
On Tue, May 02, 2017 at 11:03:34AM +0200, Boris Brezillon wrote: > On Tue, 2 May 2017 07:47:40 +0200 > Christophe LEROY <christophe.leroy@c-s.fr> wrote: > > > Le 01/05/2017 à 23:46, Brian Norris a écrit : > > > On Fri, Feb 10, 2017 at 03:01:10PM +0100, Christophe Leroy wrote: > > >> On some hardware, the nCE signal is wired to the ChipSelect associated > > >> to bus address of the NAND, so it is automatically driven during the > > >> memory access and it is not managed by a GPIO. > > >> > > >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > > > > > Not really a problem with this patch exactly, but FYI you're only making > > > this optional for the non-DT case. For device tree, this is kinda hard > > > to do, since the current binding suggests we retrieve the GPIOs based on > > > index position, not by name. So if you leave one off...I guess we well > > > just be off-by-1 on the indeces until we hit a non-optional one...which > > > I guess is "CLE". > > > > > > If we wanted this to work for DT, we'd need to extend this driver (and > > > binding doc) to support requesting GPIOs by name. > > > > > > > It works for me with devicetree. > > > > I have the following definition in my DT: > > > > nand@1,0 { > > compatible = "gpio-control-nand"; > > reg = <1 0x0 0x01>; > > #address-cells = <1>; > > #size-cells = <1>; > > gpios = <&qe_pio_c 24 1 // RDY > > 0 // nCE > > &qe_pio_c 26 1 // ALE > > &qe_pio_c 25 1 // CLE > > 0>; // nwp > > }; > > > > Yep, it's perfectly fine to have 'empty' gpio entries (entries with > phandle set to 0/NULL), we're using this trick in the atmel_nand > driver as well.
I wasn't aware. In that case, you need to change the binding doc to note that nCE is optional now.
Brian
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