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

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Date:	Tue, 18 Aug 2009 17:40:03 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	Ian Molton <ian@...menth.co.uk>
Cc:	Guennadi Liakhovetski <g.liakhovetski@....de>,
	pHilipp Zabel <philipp.zabel@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	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 Thu, Aug 6, 2009 at 8:06 AM, Ian Molton<ian@...menth.co.uk> wrote:
> Ok, so then your controller (unless it uses a different scheme altogether
> for the card clock divider) probably has a max card clock of 12MHz and a min
> of 24/512MHz.

Allright, I've now tested the tmio_mmc driver on a ms7724se board. In
the current configuration the tmio_mmc block is driven by a 83 Mhz
clock. We can change the frequency of this clock but it will affect
other hardware blocks as well so I'd rather not unless I really have
to.

> I'm fine with that. If someone who _has_ this hardware could get a 'scope on
> the card clock and see what frequencies actually appear out there, I'd
> _really_ appreciate it.

I've done some measurements with my Fluke 123 Scopemeter. It's limited
to 20 MHz so I didn't measure all combinations. I hooked it up to pin
5 of CN7 on the ms7724se board. In total I did 7 measurements, with
XSHIFT from 0 to 6. One line per measurement below. The number on the
far right is the value from the scope.

using clock 162760 (162760, 83333332) [162760] 0x0180 -> 162.7 kHz
using clock 325520 (162760, 83333332) [325520] 0x0140 -> 0.326 MHz
using clock 651040 (162760, 83333332) [651040] 0x0120 -> 0.651 MHz
using clock 1302080 (162760, 83333332) [1302080] 0x0110 -> 01.30 MHz
using clock 2604160 (162760, 83333332) [2604160] 0x0108 -> 02.61 MHz
using clock 5208320 (162760, 83333332) [5208320] 0x0104 -> 05.21 MHz
using clock 10416640 (162760, 83333332) [10416640] 0x0102 -> 10.42 MHz

Everything seems to work as expected what I can tell. The frequencies match.

I've attached a patch which shows details of the printouts. Hopefully
it includes all you need.

FYI, I needed to modify the tmio_mmc driver to change the
dev->num_resources check in probe from 3 to 2 to support the SuperH
hardware. Can you please roll in that change and send an updated
version of your "MMC / MFD / Clocks" patch whenever you have time?

Thanks for your help!

Cheers,

/ magnus

Download attachment "linux-2.6.32-pre-sh-se7724-tmio-measure-hack-20090818.patch" of type "application/octet-stream" (863 bytes)