[PATCH 3/6] tty: serial: 8250 core: add runtime pm
From: tony@atomide.com (Tony Lindgren)
Date: 2014-07-10 06:28:14
Also in:
linux-omap, linux-serial, lkml
* Sebastian Andrzej Siewior [off-list ref] [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.
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quoted hunk ↗ jump to hunk
--- 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