Re: [PATCH 2.6.21-rc1] serial: serial_txx9 driver update
From: Atsushi Nemoto
Date: Wed Feb 21 2007 - 12:03:14 EST
On Wed, 21 Feb 2007 16:48:26 +0000, Alan <alan@xxxxxxxxxxxxxxxxxxx> wrote:
> > +#ifdef CONFIG_CPU_TX49XX
> > + /* TX4925 BUG WORKAROUND. Accessing SIOC register
> > + * immediately after soft reset causes bus error. */
> > + iob();
> > + udelay(1);
> > +#endif
> Given this costs 1uS in a path that is not performance critical is it
> worth putting the #ifdef/#endif in instead of having one set of code that
> works for all ?
Thank you for review. I'll drop the #ifdef. Also I'll replace iob()
with mmiowb() since it is MIPS specific.
> > + while (sio_in(up, TXX9_SIFCR) & TXX9_SIFCR_SWRST)
> > + ;
> Suppose it doesn't clear ? Should also use cpu_relax() in busy loops
> so any processor variant with power management can do the right thing.
Then I'll put udelay() and a timeout counter for it. If udelay() was
in the busy loop, cpu_relax() is still recommended?
Here is a patch on top of the previous one. If this was OK I'll fold
it into one patch.
@@ -277,16 +277,15 @@ static void serial_txx9_enable_ms(struct
static void serial_txx9_initialize(struct uart_port *port)
struct uart_txx9_port *up = (struct uart_txx9_port *)port;
+ unsigned int tmout = 10000;
sio_out(up, TXX9_SIFCR, TXX9_SIFCR_SWRST);
/* TX4925 BUG WORKAROUND. Accessing SIOC register
* immediately after soft reset causes bus error. */
- while (sio_in(up, TXX9_SIFCR) & TXX9_SIFCR_SWRST)
+ while ((sio_in(up, TXX9_SIFCR) & TXX9_SIFCR_SWRST) && --tmout)
/* TX Int by FIFO Empty, RX Int by Receiving 1 char. */
TXX9_SIFCR_TDIL_MAX | TXX9_SIFCR_RDIL_1);
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