Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753556AbcCZSQP (ORCPT ); Sat, 26 Mar 2016 14:16:15 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:35547 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752887AbcCZSQO (ORCPT ); Sat, 26 Mar 2016 14:16:14 -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> CC: , Rob Herring , Alexey Brodkin From: Vladimir Zapolskiy Message-ID: <56F6D1E9.3050606@mentor.com> Date: Sat, 26 Mar 2016 20:16:09 +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: <56F6D083.1020402@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: 2653 Lines: 71 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. -- With best wishes, Vladimir