linux-kernel - Re: [patch 2.6.25-rc2-git 1/2] atmel

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Message-Id: <20080225010310.B59E98E4B8@adsl-69-226-248-13.dsl.pltn13.pacbell.net>
Date:	Sun, 24 Feb 2008 17:03:10 -0800
From:	David Brownell <david-b@...bell.net>
To:	hskinnemoen@...el.com
Cc:	nicolas.ferre@....atmel.com, linux@...im.org.za,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [patch 2.6.25-rc2-git 1/2] atmel_tc library

> > > > Note that this won't be usable until the AT91 and AT32 platforms
> > > > incorporate patches to configure the relevant platform devices.
> > > > Those changes are probably 2.6.26 material.
> > 
> > More specifically (and all those patches are available now):
> > 
> >  - AT91 needs clocksource/clockevent support for the SAM9 PIT timer;
> >  - AVR32 needs more extensive clocksource/clockevent updates;
>
> Which reminds me...you were talking about a patch that adds oneshot
> support for the count/compare clocksource and more cleanups, but I
> don't think I've seen it...?

I avoid sending non-working patches, and hadn't made time to
work on that issue recently.


> Yes, getting the fundamental stuff into mainline now would help a lot.

Or at least, towards the front of the merge queue, ahead of
the various platform-specific patches.


> But I was thinking about Linus' suggestions that we exploit the
> distributed nature of git and do cross-tree merges to synchronize
> changes to common code.
>
> Setting up a separate git tree would allow the changes to go into the
> arm tree without littering it with possibly unstable avr32 changes as
> well, and it would allow me to merge them and put more stuff on top.

Doing that with ARM patches is Russell's call; he hasn't been too
keen on merging from non-Linus GIT trees when that came up before.


> > > > +#define ATMEL_TC_BMR	0xc4		/* TC Block Mode Register */
> > > > +#define     ATMEL_TC_TC0XC0S	(3 << 0)	/* external clock 0 source */
> > > > +#define        ATMEL_TC_TC0XC0S_TCLK0	(0 << 0)
> > >
> > > Hmm. Indentation using spaces? I didn't know you were into that sort of
> > > thing ;-)
> > 
> > It's way better than indenting off the right margin of the page!
>
> I've never really seen the point of indenting those defines at all.

Without them, it's harder to discern the logical structure of
all the various bitfields and their contents.


> > > Anyway, my main issue is that I think we should add a data structure
> > > with information about each device, similar to struct ssc_device in the
> > > atmel-ssc driver. How about something like this?
> > >
> > > struct atmel_tc_block {
> > > 	void __iomem		*regs;	/* non-NULL when busy */
> > > 	struct platform_device	*pdev;
> > > 	struct clk		*clk[3];
> > > 	struct list_head	node;
> > > };
> > 
> > And per-channel IRQs too...
>
> I thought about that, but while the driver can safely call clk_enable()
> on the same clock several times, I'm not sure if it's such a great idea
> to call request_irq() on the same interrupt several times. So the
> driver probably needs to know how many irqs there really are and might
> as well use platform_get_irq() to find out.

I thought the whole point of passing the clocks was to avoid needing
to ask for them!!  If trying one or three platform_get_irq() calls is
OK, then surely trying one or three clk_get() calls is also OK...

- Dave


> > Well, if you want to take these patches off my hands and then be
> > responsible for merging them upstream, I won't object.  :)
>
> I can do that.
>
> It's getting late around here...I'll reply to your other mail tomorrow.
>
> Haavard
>
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