From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Figa Subject: Re: [PATCH 1/1] ARM: Exynos: Add generic compatible string Date: Wed, 05 Mar 2014 13:12:52 +0100 Message-ID: <531714C4.2040200@gmail.com> References: <1392809645-631-1-git-send-email-sachin.kamat@linaro.org> <201402251242.30654.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-samsung-soc-owner@vger.kernel.org To: Sachin Kamat , Arnd Bergmann Cc: Olof Johansson , Kukjin Kim , Tomasz Figa , linux-arm-kernel , Mark Rutland , "devicetree@vger.kernel.org" , Ian Campbell , Rob Herring , Grant Likely , linux-samsung-soc List-Id: devicetree@vger.kernel.org On 05.03.2014 09:25, Sachin Kamat wrote: > On 25 February 2014 17:12, Arnd Bergmann wrote: >> On Tuesday 25 February 2014, Olof Johansson wrote: >>> I disagree. I don't know what Samsung has in mind, but the revision of >>> the CPU doesn't have all that much to do with the rest of the SoC. >>> It's quite likely that some vendors (maybe not Samsung, but the same >>> concept applies) will ship 64-bit SoCs that are very similar to their >>> preceding 32-bit ones, same IP, similar busses, etc. I'm pretty sure >>> at least some vendors will do very close to that. >> >> Right. >> >>> So, if EXYNOS4 and EXYNOS5 can share a compatible value when they use >>> different CPUs, then there's no reason that whatever future 64-bit >>> ones can also share it. >> >> How about putting both 'samsung,exynos' and 'samsung,exynos4' in DT then >> and having the platform code match exynos4 and exynos5 but not exynos? >> >> That way, I think we are consistent and future-proof. Any code that needs >> to know if it's running on some exynos version can just check for the >> 'samsung,exynos' compatible value and that will work on both arm32 and >> arm64. Also, if we ever decide we want to run a 32-bit kernel on a 64-bit >> exynos, we can just add 'samsung,exynos6' (or whatever number that will >> be) to the list. >> >> My usual disclaimer for this: You should never ever consider actually >> running a 32-bit kernel on a 64-bit CPU, but at the same time there >> shouldn't be any reason why it won't work either, given that we require >> arm64 based systems to have all SoC specific code in drivers and we >> can use the same drivers on arm32. > > Kukjin, Tomasz, > > What is your opinion about Arnd's suggestion? > I would still prefer introducing a generic string for 32-bit Exynos SoCs, but I don't think it really matters a lot. I guess we can stick to just exynos4 and exynos5 compatible strings then, as long as we can merge the "board"-files and common.c together, since the code is pretty much SoC-independent now. Best regards, Tomasz