Hello Pekon, On Mon, May 12, 2014 at 9:03 AM, Gupta, Pekon <pekon@xxxxxx> wrote: > Hello, > > From: Javier Martinez Canillas [mailto:javier@xxxxxxxxxxxx] >>On Fri, May 9, 2014 at 10:46 PM, Pekon Gupta <pekon@xxxxxx> wrote: >>> From: Minal Shah <minalkshah@xxxxxxxxx> > [...] >>> +&gpmc { >>> + status = "okay"; >>> + pinctrl-names = "default"; >>> + pinctrl-0 = <&nand_flash_x16>; >>> + ranges = <0 0 0 0x1000000>; >>> + nand@0,0 { >>> + reg = <0 0 0x380>; > [...] > >>> diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi >>> index 37a0595..6af775a 100644 >>> --- a/arch/arm/boot/dts/dra7.dtsi >>> +++ b/arch/arm/boot/dts/dra7.dtsi >>> @@ -776,6 +776,26 @@ >>> interrupts = <0 343 0x4>; >>> status = "disabled"; >>> }; >>> + >>> + elm: elm@48078000 { >>> + compatible = "ti,am3352-elm"; >>> + reg = <0x48078000 0x2000>; >> >>It is really necessary to map all this 8 KB address space for GPMC registers? >> >>I don't have access to the DRA7 TRM but for example the OMAP3 TRM says >>that the GPMC module register address space size is 16 MB while in >>practice the registers use less than 1 KB (0..0x02d0 to be exact) so >>in arch/arm/boot/dts/omap3.dtsi we have: >> > These are not GPMC registers. Platforms from OMAP4 and beyond > (like AM335x, OMAP5) have another small hardware engine called ELM [1] > (Error Locater Module) in addition to GPMC, which is used for detecting > ECC errors in hardware. ELM Driver $KERNEL/drivers/mtd/devices/elm.c > Yes, I know what ELM is, I just made a mistake when adding my comments inline. I actually meant the 8KB from the following device node: > + gpmc: gpmc@50000000 { > + compatible = "ti,am3352-gpmc"; > + ti,hwmods = "gpmc"; > + reg = <0x50000000 0x2000>; > + interrupts = <GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>; > + gpmc,num-cs = <8>; > + gpmc,num-waitpins = <2>; > + #address-cells = <2>; > + #size-cells = <1>; > + status = "disabled"; > + }; > However, thanks for pointing out, this address-space for ELM is incorrect. > Last ELM register offset is 0xFC0 (ELM_ERROR_LOCATION_15_7) [1]. > And yes, comments applies to ELM register address space as well. >>gpmc: gpmc@6e000000 { >>... >> reg = <0x6e000000 0x02d0>; >>... >>}; >> >>Shouldn't this be similar (the same?) for DRA7 GPMC device node? >> > Newer platforms have upgraded version of GPMC engine which supports > BCH16 ECC scheme in hardware. Thus the GPMC address space was > expanded to include some extra registers required for BCH16 ECC [2]. > > I see and did the GPMC register space became that big to need to map 8KB? Although the smallest unit for ioremap is PAGE_SIZE and using any of these reg sizes: reg = <0x6e000000 0x02d0>; reg = <0x6e000000 0x0400>; reg = <0x6e000000 0x1000>; in practice have the same effect, DTS should describe the hardware and not an implementation detail so I think that we should use only the register size that is defined in the TRM. > > [1] http://www.ti.com/lit/gpn/am3359 (Section 7.4 to 7.4.5) > > [2] http://www.ti.com/lit/gpn/am3359 (Section 7.1 to 7.1.5) > (Though the AM335x address space mentions 0x368 as last address, > it should be 0x378. I have raised documentation bug for it). > > > with regards, pekon Best regards, Javier [0]: http://lxr.free-electrons.com/source/arch/arm/mm/ioremap.c#L334 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
