Hi Josh, On Thu, 15 Jan 2015 15:08:03 +0800 Josh Wu <josh.wu@xxxxxxxxx> wrote: > To get NFC status, we need to read the NFC command registers, which is a > 256M memory mapping address. To check the status, you just read such > address from NFC command registers. > For example, to check NFCBUSY (bit 27), you need to read 0x08000000 > (bit 27 is set to 1) of the NFC command register. > If you want to check NFCBUSY (bit 27) and NFCWR (bit 26) in same time, > you need to read 0x0c000000 (bit 27 and bit 26 are set to 1). Are NFCBUSY and NFCWR found in NFCDATA_STATUS and those found in HSMC_SR representing the same thing. If they are, I think you can just use HSMC_SR instead of NFCDATA_STATUS to check the status [1] and drop the last bit in the NFC Command Resgiters range. > > But mapping such huge memory address only for multiple NFC status check > is not very economic. > > The economic way is we check the NFC status one bit a time, then we don't > have to mapping such huge address. > > Now we reduce the memory mapping from 256M to 128M+4 (include 0x08000000), > the only difference is NFCBUSY (bit 27) status. You cannot check NFCBUSY > bit with other NFC status bit. > > Since current atmel_nand driver check the NFCBUSY status without combine > other bits, so this change (reduce 256M to 128M+4) will not be harmful. > > Signed-off-by: Josh Wu <josh.wu@xxxxxxxxx> > > --- > > arch/arm/boot/dts/sama5d3.dtsi | 2 +- > arch/arm/boot/dts/sama5d4.dtsi | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/boot/dts/sama5d3.dtsi b/arch/arm/boot/dts/sama5d3.dtsi > index d701ddd..d243732 100644 > --- a/arch/arm/boot/dts/sama5d3.dtsi > +++ b/arch/arm/boot/dts/sama5d3.dtsi > @@ -1426,7 +1426,7 @@ > #address-cells = <1>; > #size-cells = <1>; > reg = < > - 0x70000000 0x10000000 /* NFC Command Registers */ > + 0x70000000 0x08000004 /* NFC Command Registers */ This would give the following range: 0x70000000 0x08000000 Best Regards, Boris [1]http://code.bulix.org/2noozv-87724 -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- 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
