Hi Mason, On Fri, May 10, 2019 at 3:09 AM <masonccyang@xxxxxxxxxxx> wrote: > > "Sergei Shtylyov" <sergei.shtylyov@xxxxxxxxxxxxxxxxxx> > > 2019/05/10 上午 03:24 > > mark.rutland@xxxxxxx, "Rob Herring" <robh@xxxxxxxxxx>, zhengxunli@xxxxxxxxxxx > > On 05/09/2019 05:06 AM, masonccyang@xxxxxxxxxxx wrote: > > > > [...] > > >> > >> > On 4/24/19 11:23 PM, Rob Herring wrote: > > >> > >> > > On Wed, Apr 24, 2019 at 03:55:36PM +0800, Mason Yang wrote: > > >> > >> > >> Document the bindings used by the Renesas R-Car Gen3 RPC-IF MFD. > > >> > >> > >> > > >> > >> > >> Signed-off-by: Mason Yang <masonccyang@xxxxxxxxxxx> > > >> > >> > >> --- > > >> > >> > >> .../devicetree/bindings/mfd/mfd-renesas-rpc.txt | 40 ++++++ > > >> > >> ++++++++++++++++ > > >> > >> > >> 1 file changed, 40 insertions(+) > > >> > >> > >> create mode 100644 Documentation/devicetree/bindings/mfd/mfd- > > >> > >> renesas-rpc.txt > > >> > >> > >> > > >> > >> > >> diff --git a/Documentation/devicetree/bindings/mfd/mfd-renesas- > > >> > >> rpc.txt b/Documentation/devicetree/bindings/mfd/mfd-renesas-rpc.txt > > >> > >> > >> new file mode 100644 > > >> > >> > >> index 0000000..668b822 > > >> > >> > >> --- /dev/null > > >> > >> > >> +++ b/Documentation/devicetree/bindings/mfd/mfd-renesas-rpc.txt > > >> > >> > >> @@ -0,0 +1,40 @@ > > >> > >> > >> +Renesas R-Car Gen3 RPC-IF MFD Device Tree Bindings > > >> > >> > >> +-------------------------------------------------- > > >> > >> > > > > >> > >> > > Looks like a SPI flash controller from the example. What > > makes it an > > >> > >> > > MFD? > > >> > >> > > > >> > >> > It supports both SPI NOR and HyperFlash (CFI-compliant flash with > > >> > >> > different bus interface). > > >> > >> > > >> > >> Looks like you're registering one OR the other. > > >> > >> > > >> > >> Why don't you just do this from DT? > > >> > >> > > >> > >> No reason for this to be an MFD IMHO. > > >> > > > > >> > > > > >> > > okay, I will patch it back to SPI mode only. > > >> > > > >> > I don't think that's what Lee meant . The controller supports _both_ > > >> > modes , hence it would have the same compatible string. You just need to > > >> > extract the mode of operation from the DT. > > >> > > >> HiSilicon attempted to upstream something similar, only their > > >> controller provided NAND and NOR functionality. They used different > > >> compatible strings to differentiate between the varying > > >> technologies. > > >> > > >> They too tried to use MFD as a means to select between them (which was > > >> also NACKed). Not sure what they ended up doing, but the original > > >> submission and (half of) the conversation can be found at [0]. Some > > >> more of the thread continues at [1]. > > >> > > >> Hope that helps. > > >> > > >> [0] https://groups.google.com/forum/#!topic/fa.linux.kernel/F6i9o8sfOIw > > >> [1] https://marc.info/?l=devicetree&m=147669165104431&w=2 > > > > > > > > > Hi Marek, > > > > > > By Jones's comments: > > > -------------------------------------------------------------------------- > > >> From: Shunquan Lin <linshunquan1@xxxxxxxxxxxxx> > > >> > > >> This patch adds driver support for HiSilicon Flash Memory > > >> Controller(FMC). HiSilicon FMC is a multi-functions device which > > >> supports SPI Nor flash controller, SPI nand Flash controller and > > >> parallel nand flash controller. > > > > > > MFDs are for devices which span multiple subsystems. > > > > And we do! One of the subdrivers will live under drivers/spi/, the other > > under drivers/mtd/... > > > > From my point of view, I think Jones mean to MFD's subsystems are working simultaneously > at the run-time, one period of time is working for sub-device-1 and later period of time > is working for sub-device-2 and so on. > > But for RPC-IF, SPI or HF mode is decided at boot time by pins configure and later in kernel > by dtb, RPC-IF can't switch SPI and HF mode at the run time. > So far, Jones seems don't agree RPC-IF to MFD and then RPC MFD will not applied > to mfd tree by him ! There's precedence for such constructs being an MFD: please see drivers/mfd/at91-usart.c, which registers a single MFD cell for either serial or SPI. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
