From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F00F5C433F5 for ; Sat, 13 Nov 2021 21:31:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4AE26112F for ; Sat, 13 Nov 2021 21:31:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236091AbhKMVdw (ORCPT ); Sat, 13 Nov 2021 16:33:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234306AbhKMVds (ORCPT ); Sat, 13 Nov 2021 16:33:48 -0500 Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D4CBDC061766; Sat, 13 Nov 2021 13:30:54 -0800 (PST) Received: by mail-lj1-x235.google.com with SMTP id 13so26068391ljj.11; Sat, 13 Nov 2021 13:30:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=n4spAWLcpHUtmgBZOpY7TirfBUkG48sAlicEYd0Urdg=; b=gavEYbacmhTdU/FsuM9UYPoXnap2WaldpKfJmc1RuofScxxj0DpijAqkDf/Ppp5qtO UjQm+xjo9hPTjGiSiGjLBOFCFaBzjGpsM+WBXN4cNTXIt5MILjm2Bml22mQ1xGv6dFxm 59soV3Hn6tHnCmEk46b/0HIQu6AUbQA0H+uEm93R7hXUS8BmUhFdLBPmTXsY4+7ipNGd XCVraRt4HPOmoRgQBChAdv+F596W/owSDcBOToA4FnhY3Em251mYq/4dyD833rcEkw80 cg/sXi9q0eRgh877UvstbsAq/EqwAnUW+80UTw8nnDCGbHUNzzEl+UpkphPorqVQ8IEq oPqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=n4spAWLcpHUtmgBZOpY7TirfBUkG48sAlicEYd0Urdg=; b=gCR2aQ3eaDteBilbu9JyA7bjvx2PXyGQ0eZMUDg5FyCRsM2gL/UaQAneLvDk+midMo 7l5J6jlCQvJVo50t6q2WmPJxNQnOv0QlcflZ+Uonzx7Cbt5UHUCC06g+a3bqtrD8cHyt wYCHampgB2bWzPZWo23fFE8kYrgvxI8ysU/ueY2UBBDeabeqinaoNXeEV+CI4PzfZwsb nZ5TEpazr4ydXWxj+AY71Qea0sMXiDlzF6cqCe4jdeUywqltlOybbAGjVAGPIXXJmD7M xcwKeo21GfUv85vl0NTegrWiLNaAWfCFdTp46O3RZBjMa+gqxkXc+fIiaOLyG/oULNIH q41g== X-Gm-Message-State: AOAM532KMSTgpMQ6SYkM82TDphG09jI/JmIODP3j6Dd5jRwsexTes/fg PYzqFzxw1y57KJLk27lrcmY= X-Google-Smtp-Source: ABdhPJwhyP7RwNsg9+95qzNkwybOXKICuerXy4WNbzCl5hCansbERw1MujWoBErE76XVLTL4TfGYJQ== X-Received: by 2002:a2e:bc21:: with SMTP id b33mr23165340ljf.497.1636839053082; Sat, 13 Nov 2021 13:30:53 -0800 (PST) Received: from mobilestation ([95.79.188.236]) by smtp.gmail.com with ESMTPSA id a4sm594441lfo.291.2021.11.13.13.30.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 13 Nov 2021 13:30:52 -0800 (PST) Date: Sun, 14 Nov 2021 00:30:50 +0300 From: Serge Semin To: Andy Shevchenko Cc: Serge Semin , Mark Brown , Nandhini Srikandan , Andy Shevchenko , Andy Shevchenko , linux-spi , Linux Kernel Mailing List Subject: Re: [PATCH 4/4] spi: dw: Add Synopsys Component version reading and parsing Message-ID: <20211113213050.qjm7usvt43vygry4@mobilestation> References: <20211112204927.8830-1-Sergey.Semin@baikalelectronics.ru> <20211112204927.8830-5-Sergey.Semin@baikalelectronics.ru> <20211112220537.bddcab6b5zrewbg2@mobilestation> <20211113001908.yyo62jrbpbpeaxxb@mobilestation> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 13, 2021 at 03:15:41PM +0200, Andy Shevchenko wrote: > On Sat, Nov 13, 2021 at 2:19 AM Serge Semin wrote: > > On Sat, Nov 13, 2021 at 01:14:30AM +0200, Andy Shevchenko wrote: > > > On Saturday, November 13, 2021, Serge Semin wrote: > > > > On Fri, Nov 12, 2021 at 11:37:36PM +0200, Andy Shevchenko wrote: > > > > > On Fri, Nov 12, 2021 at 11:27 PM Andy Shevchenko > > > > > wrote: > > > > > > On Fri, Nov 12, 2021 at 10:52 PM Serge Semin > > > > > > wrote: > > ... > > > > > > > > + /* > > > > > > > + * Retrieve the Synopsys component version if it hasn't been > > > > specified > > > > > > > + * by the platform. Note the CoreKit version ID is encoded > > > > as a 4bytes > > > > > > > + * ASCII string enclosed with '*' symbol. > > > > > > > + */ > > > > > > > + if (!dws->ver) { > > > > > > > + u32 comp; > > > > > > > + > > > > > > > + comp = dw_readl(dws, DW_SPI_VERSION); > > > > > > > + dws->ver = (DW_SPI_GET_BYTE(comp, 3) - '0') * 100; > > > > > > > + dws->ver += (DW_SPI_GET_BYTE(comp, 2) - '0') * 10; > > > > > > > + dws->ver += (DW_SPI_GET_BYTE(comp, 1) - '0'); > > > > > > > + > > > > > > > + dev_dbg(dev, "Synopsys DWC%sSSI v%u.%02u\n", > > > > > > > + (dws->caps & DW_SPI_CAP_DWC_HSSI) ? " " : " > > > > APB ", > > > > > > > + dws->ver / 100, dws->ver % 100); > > > > > > > > > > > > > > > > Oh lą lą, first you multiply then you divide in the same piece of code! > > > > > > What's wrong with fourcc (and thus keep it in ver filed as is) ? (Also > > > > > > we have %p4cc) > > > > > > > > Please note that's just a dev_DBG() print. So division has been used > > > > in there to check whether the conversion was correct. The whole idea > > > > behind the code above it was to retrieve the Component version as a > > > > single number so then it could be used by the driver code in a simple > > > > statement with a normal integer operation. For instance in case if we > > > > need to check whether DW SSI IP-core version is greater than 1.01 we'd > > > > have something like this: if (dws->ver > 101). Here 101 looks at least > > > > close to the original 1.01. How would the statement look with four > > > > chars? Of course we could add an another macro which would look like > > > > this: > > > > #define DW_SSI_VER(_maj, _mid, _min) \ > > > > ((_maj) << 24 | (_mid) << 16 | (_min) << 8 | '*') > > > > and use it with raw version ID, like this > > > > (dws->ver > DW_SSI_VER('1', '0', '1')). But IMO it doesn't look > > > > better if not worse. > > > > Alternatively we could split the version ID into two parts with > > > > major and minor numbers. But normally one doesn't make much sense > > > > without another so each statement would need to check both of them > > > > at once anyway. So I decided to stick with a simplest solution and > > > > combined them into a single storage. Have you got a better idea of > > > > how to implement this functionality? > > > > > Then check DWC3 driver which relies on IZp version a lot. > > > > I'm still not convinced that the DWC3 solution would be better in this case. > > (I had a similar approach in mind though.) Although it might be suitable > > here seeing we could take the IP generation into account in a single > > macro. But at the same time having macros defined for each version may > > eventually turn into a clumsy set of macros space as it happened in DWC3. > > > > I don't understand what do you see wrong in the suggested here > > solution except a math in the debug string? > > The transformation ruins the fourcc [1] representation. We know that > this is an ASCII. We know the position and meaning of each from 4 > characters. > > [1]: https://en.wikipedia.org/wiki/FourCC So that four-CC thing wasn't Synopsys invention after all, but a sort of a relatively common approach. Your point finally starts making sense to me. > > > Why would you prefer the > > DWC3 approach better than the one implemented in my patch? > > You asked what is _better_ implementation than yours. It doesn't mean > the DWC3 approach fully fits here, but > - SPI DW has the same issue as DWC3 solves, i.e. different version > lines for two or more IPs of the same kind (see DWC3, DWC31, DWC32) > - it doesn't ruins 4cc > > In case if we need to print it, I would rather see something in %p4cc > implementation than customized 100500 approaches spreaded over the > entire kernel. Yep, these are the main pros of the DWC3 approach. Just to note in fact AFAICS Synopsys doesn't utilize the denoted components versioning for all its IP-cores. At least DW (G|X-G|XL-G)?MACs define either a normal one-byte component version ID (for instance version 3.3 looks as 0x33) or two-bytes with pair - IP-core and version IDs. But that likely is an exception, while the most of DWCs are indeed identified by the ASCII tuple. In our case we don't have the IP-core version explicitly encoded in the Component version register, so it is determined by the platform-specific code. With a minor effort I'll be able to just convert the DW_SPI_CAP_DWC_HSSI capability into two macros with virtual IP-core ID thus we'd have a more-or-less coherent versioning API. In this case we can retain the ASCII Version ID. Settled then. I'll send v2 with this patch reworked as you suggest. -Sergey > > > I don't really see much benefits in it: > > if (dws->ver > 101) > > or > > if (DW_SPI_VER_AFTER(dws, 101)) > > In both cases version ID isn't represented in the original > > Vendor-defined structure, like "1.01". The only part which could be > > considered as better in DWC3 approach is having a macro name, which gives > > a bit better notion about the operation. But does it really worth > > introducing a new abstraction in the driver? > > > > On the other hand we could intermix the approaches. For instance decode > > the Component version as I suggested in this patch and implement a set of > > version checking macro. Thus we won't need so many additional macro > > encoding the SSI_COMP_VERSION content. > > > > If only we could have a macro like DW_SPI_VER(dws, >=, "1.01a") with no > > performance drawbacks I'd be glad to use it. AFAIU compiler can't > > operate with the string literal symbols, thus the symbols extraction > > like "1.01a"[0] will be performed on each statement execution which isn't > > that performant comparing to a simple two integers comparison. > > > > BTW note the DWC3 macros implicitly depend on having a local variable > > with dwc name which violates the kernel coding style. > > > > > > > > + } > > > > > > > > > Have you seen this, btw? > > > > > > > > > > https://elixir.bootlin.com/linux/latest/source/drivers/ > > > > tty/serial/8250/8250_dwlib.c#L93 > > > > > > > > It doesn't utilized version ID for something functional, but just > > > > prints it to the console. So it isn't that good reference in this > > > > case. > > Depends what you would like to do with this. If it's only for > information to the developer, then it fits, if you need to compare, > then see above. > > -- > With Best Regards, > Andy Shevchenko