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[62.78.217.178]) by mx.google.com with ESMTPS id nf5sm1250129lab.3.2012.08.21.04.13.46 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 21 Aug 2012 04:13:47 -0700 (PDT) Date: Tue, 21 Aug 2012 14:09:52 +0300 From: Felipe Balbi To: Felipe Balbi Subject: Re: [RFC/PATCH 10/13] serial: omap: stick to put_autosuspend Message-ID: <20120821110951.GZ10347@arwen.pp.htv.fi> References: <1345540555-24359-1-git-send-email-balbi@ti.com> <1345540555-24359-11-git-send-email-balbi@ti.com> <20120821105702.GX10347@arwen.pp.htv.fi> <20120821110245.GY10347@arwen.pp.htv.fi> MIME-Version: 1.0 In-Reply-To: <20120821110245.GY10347@arwen.pp.htv.fi> User-Agent: Mutt/1.5.21 (2010-09-15) X-Gm-Message-State: ALoCoQl2e8f0jYJZvH4ngsqPISxgzMcc59PyKgXrb6pIqxCllGSI6bIuCDN94Vxesq7z4qN1w3rj X-Spam-Note: CRM114 invocation failed X-Spam-Score: -4.2 (----) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-4.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [74.125.149.84 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: Kevin Hilman , Tony Lindgren , Linux Kernel Mailing List , "Shilimkar, Santosh" , linux-serial@vger.kernel.org, Linux OMAP Mailing List , Shubhrajyoti Datta , Linux ARM Kernel Mailing List , alan@linux.intel.com X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: balbi@ti.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Hi, On Tue, Aug 21, 2012 at 02:02:46PM +0300, Felipe Balbi wrote: > On Tue, Aug 21, 2012 at 04:35:26PM +0530, Shilimkar, Santosh wrote: > > On Tue, Aug 21, 2012 at 4:27 PM, Felipe Balbi wrote: > > > On Tue, Aug 21, 2012 at 04:12:11PM +0530, Shilimkar, Santosh wrote: > > >> On Tue, Aug 21, 2012 at 2:45 PM, Felipe Balbi wrote: > > >> > Everytime we're done using our TTY, we want > > >> > the pm timer to be reinitilized. By sticking > > >> > to pm_runtime_pm_autosuspend() we make sure > > >> > that this will always be the case. > > >> > > > >> > Signed-off-by: Felipe Balbi > > >> > --- > > >> > drivers/tty/serial/omap-serial.c | 33 ++++++++++++++++++++++----------- > > >> > 1 file changed, 22 insertions(+), 11 deletions(-) > > >> > > > >> > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c > > >> > index 6ea24c5..458d77c 100644 > > >> > --- a/drivers/tty/serial/omap-serial.c > > >> > +++ b/drivers/tty/serial/omap-serial.c > > >> > @@ -164,7 +164,8 @@ static void serial_omap_enable_ms(struct uart_port *port) > > >> > pm_runtime_get_sync(up->dev); > > >> > up->ier |= UART_IER_MSI; > > >> > serial_out(up, UART_IER, up->ier); > > >> > - pm_runtime_put(up->dev); > > >> > + pm_runtime_mark_last_busy(up->dev); > > >> > + pm_runtime_put_autosuspend(up->dev); > > >> > } > > >> > > > >> Can you please expand the change-log a bit ? > > >> Didn't follow the time re-init part completely. > > > > > > It's really just a micro-optimization. The thing is: > > > > > > if I call pm_runtime_put(), I will not reinitialize the pm timer to > > > whatever timeout value I used. This means that pm_runtime_put() could > > > actually execute right away (if timer was about to expire when I called > > > pm_runtime_put()). While this wouldn't cause any issues, it's better to > > > reinitialize the timer and make sure if there's another > > > read/write/set_termios/whatever coming right after this, UART is still > > > powered up. > > > > > > I mean, it's really just trying to avoid context save & restore when > > > UART is still under heavy usage. > > > > > > Does it make sense ? > > > > It does. Would be good to add the above description in the change-log. > > Thanks for clarification. > > will do, cheers I have updated my branch like below. Will wait for any other comments before sending another version. commit 8ff7ab777d2bf8619328ddd43ddf2f8660dd011f Author: Felipe Balbi Date: Tue Aug 21 11:45:47 2012 +0300 serial: omap: stick to put_autosuspend Everytime we're done using our TTY, we want the pm timer to be reinitilized. By sticking to pm_runtime_pm_autosuspend() we make sure that this will always be the case. The idea behind this patch is to make sure we will always reinitialize the pm timer so that we don't fall into a situation where pm_runtime_put() expires right away (if timer was already about to expire when we made the call to pm_runtime_put()). While suspending right away wouldn't cause any issues, reinitializing the pm timer can help us avoiding unnecessary context save & restore operations (which are somewhat expensive) if there's another read/write/set_termios request coming right after. IOW, we are trying to make sure UART is still powered up while it's still under heavy usage. Acked-by: Santosh Shilimkar Signed-off-by: Felipe Balbi let me know if your Ack is still valid. diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index 6ea24c5..458d77c 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -164,7 +164,8 @@ static void serial_omap_enable_ms(struct uart_port *port) pm_runtime_get_sync(up->dev); up->ier |= UART_IER_MSI; serial_out(up, UART_IER, up->ier); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); } static void serial_omap_stop_tx(struct uart_port *port) @@ -412,7 +413,8 @@ static unsigned int serial_omap_tx_empty(struct uart_port *port) spin_lock_irqsave(&up->port.lock, flags); ret = serial_in(up, UART_LSR) & UART_LSR_TEMT ? TIOCSER_TEMT : 0; spin_unlock_irqrestore(&up->port.lock, flags); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); return ret; } @@ -424,7 +426,8 @@ static unsigned int serial_omap_get_mctrl(struct uart_port *port) pm_runtime_get_sync(up->dev); status = check_modem_status(up); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); dev_dbg(up->port.dev, "serial_omap_get_mctrl+%d\n", up->port.line); @@ -460,7 +463,8 @@ static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl) up->mcr = serial_in(up, UART_MCR); up->mcr |= mcr; serial_out(up, UART_MCR, up->mcr); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); } static void serial_omap_break_ctl(struct uart_port *port, int break_state) @@ -477,7 +481,8 @@ static void serial_omap_break_ctl(struct uart_port *port, int break_state) up->lcr &= ~UART_LCR_SBC; serial_out(up, UART_LCR, up->lcr); spin_unlock_irqrestore(&up->port.lock, flags); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); } static int serial_omap_startup(struct uart_port *port) @@ -575,7 +580,8 @@ static void serial_omap_shutdown(struct uart_port *port) if (serial_in(up, UART_LSR) & UART_LSR_DR) (void) serial_in(up, UART_RX); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); free_irq(up->port.irq, up); } @@ -846,7 +852,8 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios, serial_omap_configure_xonxoff(up, termios); spin_unlock_irqrestore(&up->port.lock, flags); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); dev_dbg(up->port.dev, "serial_omap_set_termios+%d\n", up->port.line); } @@ -877,7 +884,8 @@ serial_omap_pm(struct uart_port *port, unsigned int state, pm_runtime_allow(up->dev); } - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); } static void serial_omap_release_port(struct uart_port *port) @@ -959,7 +967,8 @@ static void serial_omap_poll_put_char(struct uart_port *port, unsigned char ch) pm_runtime_get_sync(up->dev); wait_for_xmitr(up); serial_out(up, UART_TX, ch); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); } static int serial_omap_poll_get_char(struct uart_port *port) @@ -973,7 +982,8 @@ static int serial_omap_poll_get_char(struct uart_port *port) return NO_POLL_CHAR; status = serial_in(up, UART_RX); - pm_runtime_put(up->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); return status; } @@ -1305,7 +1315,8 @@ static int serial_omap_probe(struct platform_device *pdev) if (ret != 0) goto err_add_port; - pm_runtime_put(&pdev->dev); + pm_runtime_mark_last_busy(up->dev); + pm_runtime_put_autosuspend(up->dev); platform_set_drvdata(pdev, up); return 0;