Messages in this thread | | | Date | Thu, 30 Jan 2014 09:38:14 +0100 | From | boris brezillon dev <> | Subject | Re: [linux-sunxi] Re: [RFC PATCH v2 09/14] mtd: nand: add sunxi NFC dt bindings doc |
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Hello Henrik,
On 29/01/2014 23:37, Henrik Nordström wrote: > ons 2014-01-29 klockan 11:11 -0600 skrev Rob Herring: > >> Isn't allwinner,rb implied by a lack of rb-gpios property. Or no R/B >> pin is an option? If so, don't you need some fixed time delay >> properties like max erase time? >> >> rb-gpios could be added to the generic nand binding as well. > The Allwinner NAND controller have dedicated RB pins when NAND is > enabled, only MUXed with other functions when NAND is not enabled. > > Leaving RB unconnected is not a valid hardware configuration. The > controller internal timing engine depends on being able to sense RB to > sequence NAND commands properly.
This is not true (at least in this driver). It was in yuq's driver because he was using the NFC_WAIT_FLAG ,and in this case the controller wait for the native R/B pin to be high before considering the CMD is complete.
This driver choose the appropriate way to test the R/B state of the NAND chip according to what was specified in the DT: - allwinner,rb: native R/B id. These pins will be used by the NAND controller to test the R/B state. Only 0 and 1 are valid because the NAND controller only support 2 R/B pins. - rb-gpios: gpio used for R/B tests. This is a simple GPIO and will use the GPIO subsystem to test the R/B pin state. - none: the NAND base code will wait some time before and send STATUS cmd to the NAND to check its status.
BTW, the controller supports 8 CS (8 NAND chips), but only have 2 native R/B pins, this means you'll have to use the GPIO or standard GET_STATUS method if you connect 3 or more NAND chips.
And for the record, I still think the rb-gpios property (or whatever common name you choose: nand-rb-gpios ?) should be part of the generic NAND binding, because other controllers (at least the atmel one :)) use GPIOs to test R/B state.
Best Regards,
Boris
> > Regards > Henrik >
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