linux-kernel - Re: MMC: Make the configuration memory resource optional

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Date:	Wed, 5 Aug 2009 15:33:11 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Ian Molton <ian@...menth.co.uk>
cc:	pHilipp Zabel <philipp.zabel@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Pierre Ossman <drzeus@...eus.cx>
Subject: Re: MMC: Make the configuration memory resource optional

Hi Ian

On Mon, 3 Aug 2009, Ian Molton wrote:

> Guennadi Liakhovetski wrote:
> 
> > > I cant see _why_ this should be a problem, as this disables the card
> > > clock,
> > > not HCLK. Could you debug further in tmio_mmc_clk_stop() please and see if
> > > reordering only one of the two IO accesses cures this?
> > 
> > Not sure I understood the "reordering only one of the two IO accesses"
> > correctly, but I swapped the two sd_ctrl_write16() calls in
> > tmio_mmc_clk_stop() and no, it didn't cure the problem.
> 
> I meant can you reorder them so that only one or the other is after the reset.
> Thus eliminating one  (perhaps) as the cause of the problem.

With my patches the tmio_mmc_clk_stop() function looked like this 
(pseudocode):

tmio_mmc_clk_stop()
{
	CTL_CLK_AND_WAIT_CTL = 0x0000;
	msleep(10);
	CTL_SD_CARD_CLK_CTL &= ~0x0100;
	msleep(10);
	clk_disable(clk);
}

I splitted the clk_disable() call out in a separate function and moved 
_only_ it after the reset() call - it worked too. Does this answer your 
question?

> Does your chip actually use the tmio-type reset, or has it a hard reset line
> or something?

No idea. As you know, this is not a separate chip, it is a built in 
controller into the sh7722 (probably, also other) SuperH SoC, so, I doubt 
it has a separate external reset line. Just like Magnus I have no 
datasheet for that block in SoC.

> Also is your issue that the driver doesnt work, or that you cant access
> registers from something like userspace ?

The driver doesn't work. Which means in this case - no interrupts, the mmc 
tasklet in in "D."

Thanks
Guennadi
---
Guennadi Liakhovetski
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