Re: [PATCH 2/3] serial: 8250_aspeed_vuart: initialize vuart->port in aspeed_vuart_probe()

[Zev Weiss]

On Wed, May 12, 2021 at 08:34:06PM CDT, Andrew Jeffery wrote:
> On Mon, 10 May 2021, at 11:12, Zev Weiss wrote:
> > Previously this had only been initialized if we hit the throttling path
> > in aspeed_vuart_handle_irq(); moving it to the probe function is a
> > slight consistency improvement and avoids redundant reinitialization in
> > the interrupt handler.  It also serves as preparation for converting the
> > driver's I/O accesses to use port->port.membase instead of its own
> > vuart->regs.
> >
> > Signed-off-by: Zev Weiss <zev@xxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/tty/serial/8250/8250_aspeed_vuart.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > index 9e8b2e8e32b6..249164dc397b 100644
> > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > @@ -349,11 +349,9 @@ static int aspeed_vuart_handle_irq(struct
> > uart_port *port)
> >  			struct aspeed_vuart *vuart = port->private_data;
> >  			__aspeed_vuart_set_throttle(up, true);
> >
> > -			if (!timer_pending(&vuart->unthrottle_timer)) {
> > -				vuart->port = up;
> > +			if (!timer_pending(&vuart->unthrottle_timer))
> >  				mod_timer(&vuart->unthrottle_timer,
> >  					  jiffies + unthrottle_timeout);
> > -			}
> >
> >  		} else {
> >  			count = min(space, 256);
> > @@ -511,6 +509,7 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
> >  		goto err_clk_disable;
> >
> >  	vuart->line = rc;
> > +	vuart->port = serial8250_get_port(vuart->line);
>
> The documentation of serial8250_get_port() is somewhat concerning wrt
> the use:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/8250/8250_core.c?h=v5.13-rc1#n399

Hmm, good point -- though despite that comment it looks like there is 
some existing code using it outside of suspend/resume callbacks (in 
8250_pci.c and 8250_pnp.c).  I'm not certain if those would necessarily 
be considered good precedent to follow for this, but I don't see any 
obvious better way of getting hold of the corresponding uart_8250_port 
(or its port.membase).

I did receive a notification that Greg had added this series to his 
tty-testing branch; not sure if that means he thinks it's OK or if it 
just kind of slipped by unnoticed though.

> However, given the existing behaviour it shouldn't be problematic?

"existing behaviour" referring to what here?


Thanks,
Zev