On Mon, Mar 28, 2016 at 11:16 AM, Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx> wrote: > Hi, > > On 28.03.2016 15:50, Marek Vasut wrote: >> On 03/28/2016 12:34 PM, Jaehoon Chung wrote: >>> Hi, >> >> Hi, >> >> [...] >> >>>>>>>>>> That said, I would rather prefer to see "snps,dw-mshc" prefix on description >>>>>>>>>> of an MMC controller found on SoCFPGA series, "altr,socfpga-dw-mshc" seems >>>>>>>>>> to be redundant. >>> >>> Yes..it's redundant..i should be combined to "snps,dw-mshc". >> >> Should the compat string be >> compatible = "altr,socfpga-dw-mshc", "snps,dw-mshc"; >> or just >> compatible = "snps,dw-mshc"; >> ? >> >> I am under the impression that a soc-specific identifier in addition to >> a generic one (used by the driver compat table) is a good idea, because >> it can help discerning the IP block from a generic one if needed at some >> future point in time. It will also not break the DT for systems >> which may depend on the non-generic compat, like *BSDs and such. >> >> What do you think ? (btw this is very much my question in this thread) > > IMO just 'compatible = "snps,dw-mshc"' is good enough, if it completely > describes the IP block on SoCFGPA --- and from what I get it is the case. > You can add a SoC-specific compatible if it is needed later on, and to my > taste only if SoC specific features can not be covered by properties. You can add the SoC-specific compatible string to the kernel later on. You may not be able to update your DTB later on. So the specific compatible strings need to be in the DT from the start. There's no set rule on properties vs. implied by a compatible string, but generally if it is fixed in the SoC, get the information based on the compatible string. If it is a board level decision or has to be tuned, then use a property. > The same sole "snps,dw-mshc" compatible is specified for NXP LPC18xx/43xx, > ZTE ZX and HiSilicon ARM SoCs. They should be fixed. > Another similar example is ARM PrimeCell PLxxx IP blocks, as far as > I know there is no SoC-specific compatibles/aliases for PrimeCell IP blocks. There are some for ST variants I think. PrimeCell blocks are a bit different in that they generally pretty simple blocks, have not changed much, and they have a standard ID register that has been sufficient for determining differences. And we have a standard way to override the ID register when it is wrong. Look at recent patches for Denali NAND controller if you want an example of why IP version registers (or compatible strings) can't be trusted. Once you get into IP blocks with lots of configuration options, complicated clocking, power domains, and with phys on the front end, then you hit all the integration differences. Rob -- 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
