Re: DT GPMC SRAM and NOR flash support ?

[Jon Hunter <jon-hunter@ti.com>]

On 02/07/2013 03:51 AM, Mark Jackson wrote:
> Okay ... I have made some progress, but it's not ideal.
> 
> Currently I've hacked the GPMC DT driver (gpmc_probe_dt(), etc) so it now handles setting up the
> chip selects and timings for NOR devices, e.g.
> 
> 		gpmc: gpmc@50000000 {
> 			status = "okay";
> 			ranges = <0 0 0x08000000 0x08000000>;	/* CS0: NOR 16M */
> 			
> 			nor@0,0 {
> 				compatible = "spansion,s29gl064n90t", "cfi-flash";
> 				reg = <0 0 0>;
> 				bank-width = <2>;
> 
> 				gpmc,sync-clk = <0>;
> 				gpmc,cs-on = <10>;
> 				gpmc,cs-rd-off = <150>;
> 				gpmc,cs-wr-off = <150>;
> 				gpmc,adv-on = <10>;
> 				gpmc,adv-rd-off = <10>;
> 				gpmc,adv-wr-off = <10>;
> 				gpmc,oe-on = <30>;
> 				gpmc,oe-off = <150>;
> 				gpmc,we-on = <30>;
> 				gpmc,we-off = <150>;
> 				gpmc,rd-cycle = <150>;
> 				gpmc,wr-cycle = <150>;
> 				gpmc,access = <130>;
> 				gpmc,page-burst-access = <10>;
> 				gpmc,cycle2cycle-diff = <1>;
> 				gpmc,cycle2cycle-same = <1>;
> 				gpmc,cycle2cycle-delay = <10>;
> 				gpmc,wr-data-mux-bus = <60>;
> 			};
> 		};
> 
> But the physmap driver (of_flash_probe()) is unable to use this information.  It seems that although
> I can call of_flash_probe() from my NOR setup code, the platform_device being reference is wrong.
> 
> The platform_device passed to my gpmc_probe_nor_child() routine from gpmc_probe_dt() points to my
> gpmc entry (above), but the physmap probe requires its own DT entry (rather than a node child such
> as my NOR entry with the GPMC device entry).
> 
> So I need to have any extra entry in the DT file as follows:-
> 
> 	nor-flash@08000000 {
> 		compatible = "spansion,s29gl064n90t", "cfi-flash";
> 		reg = <0x08000000 0x00800000>;
> 		bank-width = <2>;
> 	};
> 
> So the GPMC entry handles all the chip select and timing setup, but the 2nd entry is the only one
> the physmap driver can see.
> 
> Would it be acceptable to re-code of_flash_probe() to allow either a child device_node to be passed
> or a platform_device ?

Ideally, it should be a child device of the gpmc so that if the gpmc
device fails to init correctly, the child is not registered.

I need to think about this some more to figure out the best way to
handle nor.

Cheers
Jon