linux-kernel - Re: [PATCH]: Atmel Serial Console interrupt handler splitup

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Date:	Tue, 18 Dec 2007 10:07:24 +0100
From:	Haavard Skinnemoen <hskinnemoen@...el.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Remy Bohmer <linux@...mer.net>, linux-kernel@...r.kernel.org,
	ARM Linux Mailing List 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	Andrew Victor <linux@...im.org.za>,
	Steven Rostedt <rostedt@...dmis.org>,
	RT <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH]: Atmel Serial Console interrupt handler splitup

On Mon, 17 Dec 2007 23:49:32 +0000
Russell King - ARM Linux <linux@....linux.org.uk> wrote:

> On Mon, Dec 17, 2007 at 09:56:30PM +0100, Remy Bohmer wrote:
> > > > +#define lread(port)          __raw_readl(port)
> > > > +#define lwrite(v, port)              __raw_writel(v, port)
> > >
> > > Why is this necessary, and what does 'l' stand for?
> > 
> > There is a huge list of macros below these definitions. By doing it
> > this way, the macros still fit on 80 characters wide, while without
> > them, I had split up the macros over several lines, which does not
> > make it more readable. That's all.
> > 'l' refers at the last letter of __raw_readl, and writel. Nothing special.
> 
> So why not keep to the Linux convention?  How about at_readl() and
> at_writel() ?

Something like this perhaps?

#define at_readl(port, off)	__raw_readl((port)->membase + (off))
#define at_writel(v, port, off)	__raw_writel(v, (port)->membase + (off))

#define UART_PUT_CR(port, v)	at_writel(v, port, ATMEL_US_CR)
#define UART_PUT_MR(port, v)	at_writel(v, port, ATMEL_US_MR)
#define UART_PUT_IER(port, v)	at_writel(v, port, ATMEL_US_IER)
#define UART_PUT_IDR(port, v)	at_writel(v, port, ATMEL_US_IDR)
#define UART_PUT_CHAR(port, v)	at_writel(v, port, ATMEL_US_THR)
#define UART_PUT_BRGR(port, v)	at_writel(v, port, ATMEL_US_BRGR)
#define UART_PUT_RTOR(port, v)	at_writel(v, port, ATMEL_US_RTOR)

That said, I wonder if it may actually be nicer to just use
at_writel()/at_readl() throughout the driver...but that's for a later
cleanup.

> > >
> > > > +     while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
> > > > +             barrier();
> > >
> > > Should probably use cpu_relax(), but it's probably out of scope for a
> > > codingstyle cleanup patch (and I don't think it matters on AVR32 or
> > > ARM.)
> > 
> > Agree.
> 
> Even though it doesn't matter at the moment, I rather like to think a
> bit about the future.  If the kernel has a simple and cheap mechanism
> there's no reason to avoid using it.

I can do it in a separate patch.

> > 
> > > >       /*
> > > > -      *      First, save IMR and then disable interrupts
> > > > +      *      First, save IMR and then disable interrupts
> > > >        */
> > > >       imr = UART_GET_IMR(port);       /* get interrupt mask */
> > > >       UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY);
> > > > @@ -790,30 +828,32 @@ static void atmel_console_write(struct c
> > > >       uart_console_write(port, s, count, atmel_console_putchar);
> > > >
> > > >       /*
> > > > -      *      Finally, wait for transmitter to become empty
> > > > -      *      and restore IMR
> > > > +      *      Finally, wait for transmitter to become empty
> > > > +      *      and restore IMR
> > > >        */
> > >
> > > Looks like you're replacing TABs with spaces. Why?
> > 
> > ????
> 
> I think someone's mailer might be messing with the patches.  The above
> removed and added lines appear to be identical.

Yes, the difference was wiped out after a few times back and forth. It
was visible (or...not actually visible, but you know how to detect
these things) in the first couple of e-mails.

Haavard
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