Re: [PATCH] serial: 8250: Fix mismerge regarding serial_lsr_in()

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On Thu, Feb 02, 2023 at 01:26:08PM +0200, Ilpo Järvinen wrote:
> On Thu, 2 Feb 2023, Uwe Kleine-König wrote:
> 
> > The relevant history introducing serial_lsr_in() looks as follows:
> > 
> > 	$ git log --graph --oneline --boundary 9fafe733514b..df36f3e3fbb7 -- drivers/tty/serial/8250/8250_port.c
> > 	*   df36f3e3fbb7 Merge tag 'v5.19-rc3' into tty-next
> > 	|\
> > 	| * be03b0651ffd serial: 8250: Store to lsr_save_flags after lsr read
> > 	* | ...
> > 	* | bdb70c424df1 serial: 8250: Create serial_lsr_in()
> > 	* | ce338e4477cf serial: 8250: Store to lsr_save_flags after lsr read
> > 	* | ...
> > 	|/
> > 	o 9fafe733514b tty: remove CMSPAR ifdefs
> > 
> > So the patch "serial: 8250: Store to lsr_save_flags after lsr read" was
> > introduced twice and in one branch it was followed up by commit
> > bdb70c424df1 ("serial: 8250: Create serial_lsr_in()") which moved
> > explicit lsr_saved_flags handling into a new function serial_lsr_in().
> > When the two branches were merged in commit df36f3e3fbb7, we got both,
> > serial_lsr_in() and the explicit lsr_saved_flags handling.
> > 
> > So drop the explicit lsr_saved_flags handling.
> > 
> > Fixes: df36f3e3fbb7 ("Merge tag 'v5.19-rc3' into tty-next")
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > ---
> >  drivers/tty/serial/8250/8250_port.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> > index 33be7aad11ef..e61753c295d5 100644
> > --- a/drivers/tty/serial/8250/8250_port.c
> > +++ b/drivers/tty/serial/8250/8250_port.c
> > @@ -1512,8 +1512,6 @@ static inline void __stop_tx(struct uart_8250_port *p)
> >  		u16 lsr = serial_lsr_in(p);
> >  		u64 stop_delay = 0;
> >  
> > -		p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
> > -
> >  		if (!(lsr & UART_LSR_THRE))
> >  			return;
> >  		/*
> 
> I don't know if Fixes tag is appropriate here. This fixes the mismerge 
> yes, however, the removed line itself seems harmless so there's no real 
> problem to fix.

It might make a difference if LSR_SAVE_FLAGS != p->lsr_save_mask.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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