From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [PATCH v4 00/11] drivers: PL011: add ARM SBSA Generic UART support Date: Fri, 15 May 2015 11:31:12 +0800 Message-ID: <55556880.2010207@linaro.org> References: <1431440095-5146-1-git-send-email-andre.przywara@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <1431440095-5146-1-git-send-email-andre.przywara@arm.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: Andre Przywara , rmk+kernel@arm.linux.org.uk, Greg KH , Jiri Slaby Cc: Lorenzo Pieralisi , Graeme Gregory , arnd@arndb.de, Jakub Kicinski , linux-serial@vger.kernel.org, dave.martin@arm.com, linux-arm-kernel@lists.infradead.org List-Id: linux-serial@vger.kernel.org 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Also since some basic ACPI support for ARM64 is now > upstream, I include the necessary ACPI binding as a new patch 11 > on top. > ---- > > The ARM Server Base System Architecture[1] document describes a > generic UART which is a subset of the ARM PL011 UART. > It lacks DMA support, baud rate control and modem status line > control, among other things. > The idea is to move the UART initialization and setup into the > firmware (which does this job today already) and let the kernel just > use the UART for sending and receiving characters. > > This patchset integrates support for this UART subset into the > existing PL011 driver - basically by refactoring some > functions and providing a new uart_ops structure for it. It also has > a separate probe function to be not dependent on AMBA/PrimeCell. > It provides a device tree and an ACPI binding. > Beside the obvious effect of code sharing reusing most of the PL011 > code has the advantage of not introducing another serial device > prefix, so it can go with ttyAMA, which seems to be pretty common. > As changing the baudrate and other communication parameters is not > specified for the SBSA UART, any userland attempt will be denied by > the kernel. The device-tree provided fixed baud rate will be > reported, so stty for instance prints the right value. > > This series is based on Greg's tty-next branch, a git repo can > be found at [2] (branch sbsa-uart/v4). > > Patch 1/11 contains a bug fix which applies to the PL011 part also, > it should be considered regardless of the rest of the series. > According to Russell this is still racy, but still better than the > current solution. > Patch 2-7 refactor some PL011 functions by splitting them up into > smaller pieces, so that most of the code can be reused later by the > SBSA part. > Patch 8 and 9 introduce two new properties for the vendor structure, > this is for SBSA functionality which cannot be controlled by > separate uart_ops members only. > Patch 10 then finally drops in the SBSA specific code, by providing > a new uart_ops, vendor struct and probe function for it. Also the new > device tree binding is documented. > Patch 11 adds the necessary ACPI boilerplate. > > For testing you should be able to take any hardware which has a PL011 > and change the DT to use a "arm,sbsa-uart" compatible string and the > baud rate with the "current-speed" property. > Of course testing with a real SBSA Generic UART is welcomed - as well > as regression testing with any PL011 implementation. > I tested this on a FastModel, a Juno and a Midway machine, both in > PL011 and in (DT-emulated) SBSA mode. Tested-by: Hanjun Guo in ACPI case with device HID of ARMH0011 in DSDT. Hanjun