From: Vladimir Zapolskiy Subject: Re: ARC dw-mshc binding compat string Date: Sat, 26 Mar 2016 20:16:09 +0200 Message-ID: <56F6D1E9.3050606@mentor.com> References: <56F66121.8050507@denx.de> <56F6C639.5000301@mentor.com> <56F6C71B.6070002@denx.de> <56F6CC68.5040408@mentor.com> <56F6D083.1020402@denx.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <56F6D083.1020402@denx.de> Sender: linux-kernel-owner@vger.kernel.org To: Marek Vasut , "devicetree@vger.kernel.org" Cc: linux-kernel@vger.kernel.org, Rob Herring , Alexey Brodkin List-Id: devicetree@vger.kernel.org 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.