On 11/02/2012 03:23 PM, Daniel Mack wrote: > On 02.11.2012 20:57, Jon Hunter wrote: >> On 11/02/2012 02:23 PM, Daniel Mack wrote: >>> On 02.11.2012 20:18, Jon Hunter wrote: >>>> On 11/02/2012 06:14 AM, Daniel Mack wrote: > >>>>>>> diff --git a/Documentation/devicetree/bindings/bus/ti-gpmc.txt b/Documentation/devicetree/bindings/bus/ti-gpmc.txt >>>>>>> new file mode 100644 >>>>>>> index 0000000..6f44487 >>>>>>> --- /dev/null >>>>>>> +++ b/Documentation/devicetree/bindings/bus/ti-gpmc.txt >>>>>>> @@ -0,0 +1,73 @@ >>>>>>> +Device tree bindings for OMAP general purpose memory controllers (GPMC) >>>>>>> + >>>>>>> +The actual devices are instantiated from the child nodes of a GPMC node. >>>>>>> + >>>>>>> +Required properties: >>>>>>> + >>>>>>> + - compatible: Should be set to "ti,gpmc" >>>>>>> + - reg: A resource specifier for the register space >>>>>>> + (see the example below) >>>>>>> + - ti,hwmods: Should be set to "ti,gpmc" until the DT transition is >>>>>>> + completed. >>>>>>> + - #address-cells: Must be set to 2 to allow memory address translation >>>>>>> + - #size-cells: Must be set to 1 to allow CS address passing >>>>>>> + - ranges: Must be set up to reflect the memory layout >>>>>>> + Note that this property is not currently parsed. >>>>>>> + Calculated values derived from the contents of >>>>>>> + GPMC_CS_CONFIG7 as set up by the bootloader. That will >>>>>>> + change in the future, so be sure to fill the correct >>>>>>> + values here. >>>>>> >>>>>> I still think it would be good to add number of chip-selects and >>>>>> wait-pins here. >>>>> >>>>> The number of chip-selects can be derived from the ranges property. >>>>> Namely, each 4-value entry to this property maps to one chip-select. I >>>>> can try and make the more clear in the documentation. >>>> >>>> Yes but that only tells you how many you are using. The binding should >>>> describe the hardware and so should tell us how many chip-selects we >>>> have. We should get away from using GPMC_CS_NUM in the code. >>> >>> Maybe I don't get your point, but we only need to care for as many cs >>> lines as we actually use, right? >> >> But how many does your device have? How many clients can you support? > > Well, you state that in the ranges property. Even if the chip could in > theory support 8 CS lines - if the actual setup only uses the first one > of them, the code would only need to allocate and set up the one that is > in use. And as the entries in "ranges" are mandatory, there can actually > be no mis-allocation. Ah, I see your point now. Well typically, we have been putting the device-level peripheral info in the device's *.dtsi (ie. am33xx.dtsi) and then board specific stuff in the board *.dts file (am335x-bone.dts). So I would envision that the device-level info (reg, ti,hwmods, interrupt, num-cs) be in am33xx.dtsi and ranges be in am335x.dts. So it would still be nice to catch any badly configured ranges property in the driver by querying in the number of chip-selects. > I can still add the maximum number as a separate property, but I wanted > to outline my idea here. Is "num-cs" a good name for the property? Sounds good. >> If we know how many the device has and then we can get rid of "#define >> GPMC_CS_NUM". We currently allocate the CS by calling gpmc_cs_request(). >> Hmmm ... I now see that your patch is not calling this before >> configuring the CS and so that needs to be fixed too. > > It does implicitly, by calling gpmc_nand_init(). Yes, you are right! >> Without knowing the total CS available, how do we ensure we have the CS >> available that someone is asking for? >> >>>> What about wait-pins? >>> >>> Afaik, their use depends on the driver acting as GPMC client, right? >>> Could you point me to code that acts conditionally and that should be >>> reflected in DT? >> >> Again we need to know how many the device has. Clients may or may not >> use these. However, if a client wants one they need to request one which >> is just like a chip-select. This is not in the current driver but Afzal >> has a patch for this [1]. > > Ah, thanks for the pointer to the patch. Ok, I'll add a "num-waitpins" > property. Does that name sound appropriate? Yes, that would be great! >> Bottom line, for such hardware specific features, device tree is a good >> place to describe how many resources we have. Then we can eliminate such >> #defines from the driver code. > > Agreed. > >>> Quoting Documentation/devicetree/bindings/mtd/gpmc-nand.txt: >>> >>> For NAND specific properties such as ECC modes or bus width, >>> please refer to Documentation/devicetree/bindings/mtd/nand.txt >> >> Ok, thanks I see that now. Looking at other bindings, some also include >> these details but not all. Could be worth listing ecc-mode under >> mandatory and bus-width under optional with a reference to nand.txt >> binding. I don't think it is worth duplicating but listing the actual >> property names would be nice. > > Ok, I amended my local version. With the details above sorted out and > "num-cs" and "num-waitpins" in place, do you think we're ready for v4? Yes, thanks for doing this. Cheers Jon -- 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
