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a=rsa-sha256; c=simple/simple; d=flygoat.com; s=default; t=1596738369; bh=v6+hYB3wUB+4/fro3yDhVbBnH/mkjkFI9z9KFpiDfWY=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=FR7C13jQLja842FFA+9Mfd6g4RgDFwwYpn9p508EWXpQbJO+EEISvRkT04Yu3kjs5 8hUoJ8Za/j9z26Nqg84aOmk2fTLDqaHzLGNH4rnzeFnAZjp463C0oIv4aDmpJX9uXo mlCjH08OVtGlsQlenkaO2C+wplwCTvCERW2yA96I= Subject: Re: [PATCH] MIPS: Introduce cmdline argument writecombine= To: Tiezhu Yang Cc: Thomas Bogendoerfer , Huacai Chen , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org References: <1596697741-3561-1-git-send-email-yangtiezhu@loongson.cn> <10e04885-b775-e7db-b927-6400382fd32d@flygoat.com> <20200806101733.GA8136@alpha.franken.de> <9e563c75-ffaa-45b4-0e99-25a8b1eff828@flygoat.com> <20200806165212.GA2754@alpha.franken.de> From: Jiaxun Yang Message-ID: Date: Fri, 7 Aug 2020 02:26:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200806165212.GA2754@alpha.franken.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Rspamd-Queue-Id: E93A3419D2 X-Spamd-Result: default: False [-0.10 / 10.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; R_DKIM_ALLOW(0.00)[flygoat.com:s=default]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; R_SPF_SOFTFAIL(0.00)[~all]; RCPT_COUNT_FIVE(0.00)[5]; ML_SERVERS(-3.10)[148.251.23.173]; DKIM_TRACE(0.00)[flygoat.com:+]; DMARC_POLICY_ALLOW(0.00)[flygoat.com,none]; DMARC_POLICY_ALLOW_WITH_FAILURES(0.00)[]; RCVD_NO_TLS_LAST(0.10)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:148.251.0.0/16, country:DE]; RCVD_COUNT_TWO(0.00)[2]; MID_RHS_MATCH_FROM(0.00)[]; HFILTER_HELO_BAREIP(3.00)[148.251.23.173,1] X-Rspamd-Server: mail20.mymailcheap.com Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org 在 2020/8/7 上午12:52, Thomas Bogendoerfer 写道: > On Thu, Aug 06, 2020 at 07:56:20PM +0800, Jiaxun Yang wrote: >> Our current problem is Loongson's writecombine implementation seems buggy. >> This is our platform issue rather than target hardware issue. > ok, so simply clear cpu_data[0].writecombine for the fauly parts @Tiezhu, I don't know the exact faulty parts, could you please investigate it in Loongson? I can remember a Loongson stuff told me the issue was solved in GS464E but there are still users complaining about that. In fact I can't reproduce it in all of my test systems: 3B1500 + RS780E + R5 230 3A3000 + RS780E Laptop 3A4000 + LS7A + RX550 >> And we don't even know which hardware is known to be good. The same graphic >> card became a different story on different user's hand. > find out what is broken and add the needed workarounds then. Well, let's leave this task for Loongson company. User's community don't have the ability to trace hardware behavior precisely. >> I understood what Teizhu thought. For entry-level users, we don't want to >> trouble >> them, so we have writecombine disabled by default. However, for advanced >> user >> trying to tweak their system, we should leave a switch for them to get it >> back. > IMHO if we do it that way, we end up with millions of knobs for tweaking > broken hardware, and nobody knows what's exactly broken. Sorry I won't go > that way. Haha, that was my first impression to Linux as a primary school student. It just looks like an aircraft cockpit with thousands of knobs & switches, but to airborne you just need to control yoke and throttle. - Jiaxun