Re: MMC: Make the configuration memory resource optional

[Magnus Damm <magnus.damm@gmail.com>]

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Hi Ian!

On Thu, Aug 6, 2009 at 8:06 AM, Ian Molton<ian@mnementh.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

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--- 0007/drivers/mmc/host/tmio_mmc.c
+++ work/drivers/mmc/host/tmio_mmc.c	2009-08-18 17:03:22.000000000 +0900
@@ -35,13 +35,16 @@
 
 #include "tmio_mmc.h"
 
+#define XSHIFT 6
+#define XLIMIT (162760 << XSHIFT)
+
 static void tmio_mmc_set_clock(struct tmio_mmc_host *host, int new_clock)
 {
 	u32 clk = 0, clock;
 
 	if (new_clock) {
 		for (clock = host->mmc->f_min, clk = 0x80000080;
-			new_clock >= (clock<<1); clk >>= 1)
+		     (clock < XLIMIT) && (new_clock >= (clock<<1)); clk >>= 1)
 			clock <<= 1;
 		clk |= 0x100;
 	}
@@ -49,6 +52,10 @@ static void tmio_mmc_set_clock(struct tm
 	if(host->set_no_clk_div)
 		host->set_no_clk_div(NULL, (clk>>22) & 1);
 
+	printk("using clock %d (%d, %d) [%d] 0x%04x\n",
+	       clock, host->mmc->f_min, host->mmc->f_max, XLIMIT,
+	       clk & 0x1ff);
+
 	sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, clk & 0x1ff);
 }