Re: h1940 - kernel 2.6.20-rc1 can't read my SD card

At 10:07 AM 1/25/2007, Carlo Palma wrote:
>On Tuesday 23 January 2007 23:17, Tom Talpey wrote:
>> I am having the same problem, but I have managed to fix at least one of
>> my cards by adding a clock limit to the h1940_mmc_cfg structure in
>> mach-h1940.c. I have another card which it does not fix though (133x).
>> These cards all worked fine in the previous kernels.
>
>I think I should understand some fundamentals of the mmc layer, before to
>apply your patch. I'll report any result as soon as possible.

I figured out the reason for the failure in my high-speed cards. In the
new mmc layer, there are two commands issued to probe a high-speed
SD card's "switch". The second one fails with a CRC error. At that point
the mmc layer labels the card as dead and stops using it.

I suspect that this may be due to the SD slot on the h1940, but it could
also be a core mmc issue. In any case, limiting the maximum clock to 3MHZ,
and avoiding the problematic SD command, allows all three of my cards to
work fine again. I'd consider this a temporary workaround, until we get to
the root cause. This patch is against 2.6.20-rc5 + various of rtp's patches
but it should be pretty close for other rc's.

The patch also unconditionally enables the clock message, so you can
see things as they are probed. If a card is marked dead, its clock goes to
0MHz - a handy quick indicator. If the clock is over 3MHz, sometimes it
just hangs though, usually when starting init, or later.

Tom.

Index: kernel/arch/arm/mach-s3c2410/mach-h1940.c
===================================================================
--- kernel.orig/arch/arm/mach-s3c2410/mach-h1940.c
+++ kernel/arch/arm/mach-s3c2410/mach-h1940.c
@@ -153,6 +153,7 @@ static struct s3c24xx_mmc_platdata h1940
        .gpio_detect = S3C2410_GPF5,
        .set_power = NULL,
        .ocr_avail = MMC_VDD_32_33,
+ .f_max = 3000000, // TEMP - limit clock to 3MHz
 };
 
 
Index: kernel/drivers/mmc/mmc.c
===================================================================
--- kernel.orig/drivers/mmc/mmc.c
+++ kernel/drivers/mmc/mmc.c
@@ -368,7 +368,7 @@ static inline void mmc_set_ios(struct mm
 {
        struct mmc_ios *ios = &host->ios;
 
- pr_debug("%s: clock %uHz busmode %u powermode %u cs %u Vdd %u width %u\n",
+ /*pr_debug(*/printk(KERN_INFO "%s: clock %uHz busmode %u powermode %u cs %u Vdd %u width %u\n",
                 mmc_hostname(host), ios->clock, ios->bus_mode,
                 ios->power_mode, ios->chip_select, ios->vdd,
                 ios->bus_width);
@@ -1222,6 +1222,10 @@ static void mmc_read_switch_caps(struct
                if (status[13] & 0x02)
                        card->sw_caps.hs_max_dtr = 50000000;
 
+// TEMP
+// skip the following command, it fails with a CRC error on many cards...
+ continue;
+
                memset(&cmd, 0, sizeof(struct mmc_command));
 
                cmd.opcode = SD_SWITCH;
Received on Thu Jan 25 2007 - 21:57:26 EST