From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH 3/6] tty: serial: 8250 core: add runtime pm Date: Wed, 9 Jul 2014 23:28:12 -0700 Message-ID: <20140710062812.GF28884@atomide.com> References: <1404928177-26554-1-git-send-email-bigeasy@linutronix.de> <1404928177-26554-4-git-send-email-bigeasy@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1404928177-26554-4-git-send-email-bigeasy@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: Sebastian Andrzej Siewior Cc: linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Felipe Balbi , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, mika.westerberg@linux.intel.com List-Id: linux-serial@vger.kernel.org * Sebastian Andrzej Siewior [140709 10:52]: > While comparing the OMAP-serial and the 8250 part of this I noticed that > the the latter does not use runtime-pm. Here are the pieces. It is > basically a get before first register access and a last_busy + put after > last access. > If I understand this correct, it should do nothing as long as > pm_runtime_use_autosuspend() + pm_runtime_enable() isn't invoked on the > device. ... > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -571,7 +573,17 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > serial_out(p, UART_EFR, 0); > serial_out(p, UART_LCR, 0); > } > + > + if (!device_may_wakeup(p->port.dev)) { > + if (sleep) > + pm_runtime_forbid(p->port.dev); > + else > + pm_runtime_allow(p->port.dev); > + } > } > +out: > + pm_runtime_mark_last_busy(p->port.dev); > + pm_runtime_put_autosuspend(p->port.dev); > } The device_may_wakeup logic here is wrong as I described in the earlier thread. For runtime PM, the wake-up events should be always enabled. So the device_may_wakeup checks should be only done for suspend and resume. Regards, Tony