From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: [PATCH v4 5/5] arm64: dts: Add dts files for Hisilicon Hi6220 SoC Date: Wed, 6 May 2015 10:30:22 +0100 Message-ID: <20150506093022.GB31001@leverpostej> References: <1430827599-11560-1-git-send-email-bintian.wang@huawei.com> <1430827599-11560-6-git-send-email-bintian.wang@huawei.com> <20150505171349.GA30215@leverpostej> <5549877C.10408@huawei.com> <5549B9CC.1040709@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <5549B9CC.1040709@huawei.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Bintian Cc: "dan.zhao@hisilicon.com" , "btw@mail.itp.ac.cn" , Catalin Marinas , "wangbinghui@hisilicon.com" , Will Deacon , "huxinwei@huawei.com" , "haojian.zhuang@linaro.org" , "yanhaifeng@gmail.com" , "rob.herring@linaro.org" , "mturquette@linaro.org" , Pawel Moll , "khilman@kernel.org" , "xuwei5@hisilicon.com" , "jh80.chung@samsung.com" , "sledge.yanwei@huawei.com" , "kong.kongxinwei@hisilicon.com" , "heyunlei@huawei.com" , "w.f@huawei.com" "zhangfei.gao@linaro.org" List-Id: devicetree@vger.kernel.org On Wed, May 06, 2015 at 07:50:52AM +0100, Bintian wrote: > Hello Mark, > > On 2015/5/6 11:16, Bintian wrote: > > Hello Mark, > > > > On 2015/5/6 1:13, Mark Rutland wrote: > [...] > >>> + uart0: uart@f8015000 { /* console */ > >>> + compatible = "arm,pl011", "arm,primecell"; > >>> + reg = <0x0 0xf8015000 0x0 0x1000>; > >>> + interrupts = ; > >>> + clocks = <&ao_ctrl HI6220_UART0_PCLK>, <&ao_ctrl > >>> HI6220_UART0_PCLK>; > >>> + clock-names = "uartclk", "apb_pclk"; > >>> + }; > >> > >> In a previous discussion [1] the UART on HI6220 was described as not > >> fully PL011 compliant, with a number of differences (e.g. the FIFO > >> length). > >> > >> Given that, I feel somewhat uncomfortable with the current compatible > >> string list. What exactly are those differences? We may need a more > >> specific compatible string (even if in addition to those existing ones), > >> or perhaps other properties. > > The small system can be booted and the console also works well without > > changing any code of driver amba-pl011.c, so I think the compatible > > string is OK for this patch set. > > > > Hisilicon do some performance enhancements based on PL011, but the > > current driver "amba-pl011.c" also works on hi6220 without those > > enhancements driver code. > Checked with Hisilicon chip designer, the UART0 is used for DEBUG > console and compliant with PL011 fully. I think that given that we know the UART is not quite a PL011 we should add an additional compatible string just in case some difference crops up later that is problematic. So we'd have something like: compatible = "hisilicon,hi6220-uart", "arm,pl011", "arm,primecell"; That way we can add any optimisations or workarounds later as required. Thanks, Mark.