From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH v2 06/10] drivers: PL011: replace UART_MIS reading with _RIS & _IMSC Date: Thu, 12 Mar 2015 10:46:51 +0000 Message-ID: <20150312104651.GJ8656@n2100.arm.linux.org.uk> References: <1425491994-23913-1-git-send-email-andre.przywara@arm.com> <1425491994-23913-7-git-send-email-andre.przywara@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1425491994-23913-7-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 Cc: rob.herring@linaro.org, arnd@arndb.de, gregkh@linuxfoundation.org, linux-serial@vger.kernel.org, jslaby@suse.cz, Dave.Martin@arm.com, linux-arm-kernel@lists.infradead.org List-Id: linux-serial@vger.kernel.org On Wed, Mar 04, 2015 at 05:59:50PM +0000, Andre Przywara wrote: > The PL011 register UART_MIS is actually a bitwise AND of the > UART_RIS and the UART_MISC register. > Since the SBSA UART does not include the _MIS register, use the > two separate registers to get the same behaviour. Since we are > inside the spinlock and we read the _IMSC register only once, there > should be no race issue. Do we really need to go all the way to the hardware for this? Isn't uap->im sufficient? Reading from memory is potentially faster as it could be in the CPU caches. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.