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Date: Thu, 23 Sep 2021 18:05:36 +0300 From: Tony Lindgren <tony@...mide.com> To: Johan Hovold <johan@...nel.org> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Andy Shevchenko <andriy.shevchenko@...el.com>, Jiri Slaby <jirislaby@...nel.org>, Vignesh Raghavendra <vigneshr@...com>, linux-serial@...r.kernel.org, linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 4/6] serial: 8250: Implement prep_tx for power management * Johan Hovold <johan@...nel.org> [210923 12:50]: > On Tue, Sep 21, 2021 at 01:33:44PM +0300, Tony Lindgren wrote: > > +static int serial8250_prep_tx(struct uart_port *port) > > +{ > > + struct uart_8250_port *up = up_to_u8250p(port); > > + struct device *dev = up->port.dev; > > + int err; > > + > > + if (!(up->capabilities & UART_CAP_RPM)) > > + return 0; > > + > > + if (!pm_runtime_suspended(dev)) { > > + pm_runtime_mark_last_busy(dev); > > + return 0; > > + } > > + > > + err = pm_request_resume(dev); > > + if (err < 0) { > > + dev_warn(dev, "prep_tx wakeup failed: %d\n", err); > > + return err; > > + } > > How is this supposed to work without a runtime PM usage-counter > increment? What's to prevent the port from suspending again while it's > transmitting? Hmm yeah we should at pm_runtime_get() and pm_runtime_put() to write() unless serial8250_rpm_get() and serial8250_rpm_put() are doing it. Or pair prep with finish and deal with the usage count there. Regards, Tony
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