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Date: Wed, 9 Apr 2014 17:06:24 +0200
From: Thomas Pfaff <tpfaff@....com>
To: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
CC: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"jslaby@...e.cz" <jslaby@...e.cz>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial_core: fix uart PORT_UNKNOWN handling
On Wed, 9 Apr 2014, One Thousand Gnomes wrote:
> On Wed, 9 Apr 2014 13:22:14 +0200
> Thomas Pfaff <tpfaff@....com> wrote:
>
> > 1. uart_change_pm ist called during uart_open and calls the uart pm function
> > without checking for PORT_UNKNOWN.
>
> Removing this breaks other parts of the code assume that the port will be
> powered up (notably setserial paths). So it makes sense that
> uart_change_pm for a "none" port is a no-op but needs logic in the
> setserial path to power up a port when we move none->known and power it
> down on known->none
>
Then why not move uart_change_pm into uart_port_startup, where it will be called
when needed ?
A reworked patch is below.
> > 2. uart_shutdown is called from uart_set_info and does not check it either.
>
> I don't see why this one matters. We would have done
>
> uart_startup
> uart_port_startup
> uport->type == PORT_UNKNOWN
> return 1;
> ASYNCB_INITIALIZED is not set
>
> uart_shutdown
> ASYNCB_INITIALISED is not set
> Skip call to uart_port_shutdown
>
> So that code looks correct to me.
I agree, i have overlooked this.
Signed-off-by: Thomas Pfaff <tpfaff@....com>
---
diff -urp linux-3.14.org/drivers/tty/serial/serial_core.c linux-3.14/drivers/tty/serial/serial_core.c
--- linux-3.14.org/drivers/tty/serial/serial_core.c 2014-03-31 05:40:15.000000000 +0200
+++ linux-3.14/drivers/tty/serial/serial_core.c 2014-04-09 16:41:03.940046814 +0200
@@ -138,6 +138,11 @@ static int uart_port_startup(struct tty_
return 1;
/*
+ * Make sure the device is in D0 state.
+ */
+ uart_change_pm(state, UART_PM_STATE_ON);
+
+ /*
* Initialise and allocate the transmit and temporary
* buffer.
*/
@@ -826,25 +831,29 @@ static int uart_set_info(struct tty_stru
* If we fail to request resources for the
* new port, try to restore the old settings.
*/
- if (retval && old_type != PORT_UNKNOWN) {
+ if (retval) {
uport->iobase = old_iobase;
uport->type = old_type;
uport->hub6 = old_hub6;
uport->iotype = old_iotype;
uport->regshift = old_shift;
uport->mapbase = old_mapbase;
- retval = uport->ops->request_port(uport);
- /*
- * If we failed to restore the old settings,
- * we fail like this.
- */
- if (retval)
- uport->type = PORT_UNKNOWN;
- /*
- * We failed anyway.
- */
- retval = -EBUSY;
+ if (old_type != PORT_UNKNOWN) {
+ retval = uport->ops->request_port(uport);
+ /*
+ * If we failed to restore the old settings,
+ * we fail like this.
+ */
+ if (retval)
+ uport->type = PORT_UNKNOWN;
+
+ /*
+ * We failed anyway.
+ */
+ retval = -EBUSY;
+ }
+
/* Added to return the correct error -Ram Gupta */
goto exit;
}
@@ -1570,12 +1579,6 @@ static int uart_open(struct tty_struct *
}
/*
- * Make sure the device is in D0 state.
- */
- if (port->count == 1)
- uart_change_pm(state, UART_PM_STATE_ON);
-
- /*
* Start up the serial port.
*/
retval = uart_startup(tty, state, 0);
--
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