Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754243AbcCZUM5 (ORCPT ); Sat, 26 Mar 2016 16:12:57 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:39298 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754066AbcCZUMz (ORCPT ); Sat, 26 Mar 2016 16:12:55 -0400 Subject: Re: ARC dw-mshc binding compat string To: Marek Vasut , "devicetree@vger.kernel.org" References: <56F66121.8050507@denx.de> <56F6C639.5000301@mentor.com> <56F6C71B.6070002@denx.de> <56F6CC68.5040408@mentor.com> <56F6D083.1020402@denx.de> <56F6D1E9.3050606@mentor.com> <56F6E860.8070207@denx.de> CC: , Rob Herring , Alexey Brodkin From: Vladimir Zapolskiy Message-ID: <56F6ED41.5020908@mentor.com> Date: Sat, 26 Mar 2016 22:12:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Icedove/38.1.0 MIME-Version: 1.0 In-Reply-To: <56F6E860.8070207@denx.de> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [137.202.0.76] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3610 Lines: 90 On 26.03.2016 21:52, Marek Vasut wrote: > On 03/26/2016 07:16 PM, Vladimir Zapolskiy wrote: >> On 26.03.2016 20:10, Marek Vasut wrote: >>> On 03/26/2016 06:52 PM, Vladimir Zapolskiy wrote: >>>> Hi Marek, >>>> >>>> On 26.03.2016 19:30, Marek Vasut wrote: >>>>> On 03/26/2016 06:26 PM, Vladimir Zapolskiy wrote: >>>>>> On 26.03.2016 12:14, Marek Vasut wrote: >>>>>>> Hi! >>>>>>> >>>>>>> I noticed that arch/arc/boot/dts/axs10x_mb.dtsi uses "altr," prefix in >>>>>>> the DT compatible string: >>>>>>> >>>>>>> mmc@0x15000 { >>>>>>> compatible = "altr,socfpga-dw-mshc"; >>>>>>> reg = < 0x15000 0x400 >; >>>>>>> num-slots = < 1 >; >>>>>>> fifo-depth = < 16 >; >>>>>>> card-detect-delay = < 200 >; >>>>>>> clocks = <&apbclk>, <&mmcclk>; >>>>>>> clock-names = "biu", "ciu"; >>>>>>> interrupts = < 7 >; >>>>>>> bus-width = < 4 >; >>>>>>> }; >>>>>>> >>>>>>> I don't think this is OK, since ARC is unrelated to Altera, which is >>>>>>> what the "altr," prefix stands for. I think the socfpga-dw-mshc shim >>>>>>> should be extended with another compatibility string, something like >>>>>>> "snps,arc-dw-mshc" and the axs10x_mb.dtsi should be adjusted >>>>>>> accordingly. What do you think ? >>>>>>> >>>>>> >>>>>> There is "snps,dw-mshc" described in >>>>>> Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt and supported by >>>>>> dw_mmc host controller driver. >>>>> >>>>> Thanks, that's even better. >>>>> >>>>> btw what do you think of using altr, prefix on non-altera system, that >>>>> doesn't seem ok, right ? >>>> >>>> according to ePAPR the prefix should represent a device (IP block here >>>> I believe) manufacturer, so it should be okay to use "altr" prefix on >>>> non-Altera system, if Altera provides another hardware vendor with >>>> some own IP block. >>> >>> In this case, it's Synopsys who provides the SD/MMC/MS core to other >>> chip makers (Altera etc). >> >> Correct. >> >>>> 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. >>> >>> According to drivers/mmc/host/dw_mmc-pltfm.c , the Altera SoCFPGA one >>> "altr,socfpga-dw-mshc" and also Imagination Technology Pistacio one >>> "img,pistachio-dw-mshc" need specialty bit (SDMMC_CMD_USE_HOLD_REG), >>> while the stock one "snps,dw-mshc" does not. I am not sure if the ARC >>> one needs it as well, but most likely yes. >>> >>> I wonder if that bit is needed on some particular version of the DWMMC >>> core. In that case, should we have "snps,dw-mshc" and "snps,dw-mshc-vN" >>> binding ? Or should we use DT property to discern the need for this bit ? >>> >> >> That's the most common way to take into account peculiarities, add >> a property and handle it from the driver. > > And by "that" you mean which of those two I listed , the > "snps,dw-mshc-vN" or adding new DT prop ? > I meant to add a new property, not a new compatible, but that's just my experience. Let me say it __might__ happen that a particular change you need is specific to a particular version of the DWMMC IP (query Synopsys by the way), but more probably it might be e.g. the same IP version with a different reduced or extended configuration or a minor fix/improvement to the IP block without resulting version number bump. For example I don't remember that errata fixes in IP blocks result in a new compatible, instead there are quite common optional "quirk" properties for broken IPs -- e.g. check bindings/usb/dwc3.txt :) -- With best wishes, Vladimir