From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bintian Subject: Re: [PATCH v4 5/5] arm64: dts: Add dts files for Hisilicon Hi6220 SoC Date: Wed, 6 May 2015 18:36:07 +0800 Message-ID: <5549EE97.3020801@huawei.com> 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> <20150506093022.GB31001@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150506093022.GB31001@leverpostej> 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: Mark Rutland 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 Hello Mark, On 2015/5/6 17:30, Mark Rutland wrote: > 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. I understand and thanks for your suggestion. Can I do not do this work in this patch set? Because I got the information UART0 is PL011 compatible. Hisilicon uart engineer can do this work in the future, maybe for UART1/UART2. Thank you Mark, BR, Bintian > > Thanks, > Mark. > > . >