From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c) Date: Fri, 26 Sep 2014 14:11:17 +0100 Message-ID: <20140926131117.GR5182@n2100.arm.linux.org.uk> References: <1411150399-30902-1-git-send-email-j.uzycki@elproma.com.pl> <54256326.3080202@elproma.com.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <54256326.3080202@elproma.com.pl> Sender: linux-serial-owner@vger.kernel.org To: Janusz =?utf-8?Q?U=C5=BCycki?= Cc: Richard Genoud , Greg Kroah-Hartman , Fabio Estevam , linux-arm-kernel@lists.infradead.org, linux-serial@vger.kernel.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org On Fri, Sep 26, 2014 at 02:59:18PM +0200, Janusz U=C5=BCycki wrote: > But serial8250_get_mctrl() in 8250_core.c calls serial8250_modem_stat= us() > which calls eg. uart_handle_cts_change() even if enable_ms() wasn't c= alled. > This is the difference. > The serial8250_modem_status() is also called in the interrupt > and, what I don't understand, in serial8250_console_write(). Reading the MSR register clears the interrupts. So, whenever MSR is re= ad, you have to deal with any state changes which _would_ have been passed to the interrupt function. Plus, it's not quite as you make out above. If enable_ms() is not called, then UART_IER_MSI will not be set in up->= ier. Hence, uart_handle_cts_change() will not be called. The reason for the call in the console function is to account for the state changes during console write with CTS flow control - this again needs the MSR register to be read, and we have to account for MSR state changes after the console write has completed. --=20 =46TTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-serial"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html