[PATCH 3/3] MMC compatibility fix - OCR mask

[PATCH 3/3] MMC compatibility fix - OCR mask

[Pierre Ossman]

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This patch avoids using a emtpy OCR mask for the initial power up. Since 
some cards do not like a one bit-mask a routine has been added which 
grows the mask to three bits (one extra bit on each side) if necessary.


[-- Attachment #2: mmc-ocr.patch --]
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Index: linux-wbsd/drivers/mmc/mmc.c
===================================================================
--- linux-wbsd/drivers/mmc/mmc.c	(revision 63)
+++ linux-wbsd/drivers/mmc/mmc.c	(revision 64)
@@ -300,6 +300,31 @@
 	return ocr;
 }
 
+/*
+ * Calculate a OCR mask to use for initial scanning.
+ * All zeroes and all ones cannot be used with some cards.
+ * Just on bit cannot be used either so extend the OCR
+ * if needed.
+ */
+
+static u32 mmc_select_scan_ocr(struct mmc_host *host)
+{
+	u32 ocr;
+
+	ocr = host->ocr_avail;
+
+	/* Check if we have more than one bit */
+	if (ocr & (ocr << 1))
+		return ocr;
+	if (ocr & (ocr >> 1))
+		return ocr;
+
+	/* Extend the mask to surrounding bits */
+	ocr |= (ocr << 1) | (ocr >> 1);
+
+	return ocr;
+}
+
 static void mmc_decode_cid(struct mmc_cid *cid, u32 *resp)
 {
 	memset(cid, 0, sizeof(struct mmc_cid));
@@ -589,7 +614,9 @@
 
 		mmc_power_up(host);
 
-		err = mmc_send_op_cond(host, 0, &ocr);
+		ocr = mmc_select_scan_ocr(host);
+
+		err = mmc_send_op_cond(host, ocr, &ocr);
 		if (err != MMC_ERR_NONE)
 			return;
 

Re: [PATCH 3/3] MMC compatibility fix - OCR mask

[Russell King]

On Sat, Sep 18, 2004 at 12:00:16PM +0200, Pierre Ossman wrote:
> This patch avoids using a emtpy OCR mask for the initial power up. Since 
> some cards do not like a one bit-mask a routine has been added which 
> grows the mask to three bits (one extra bit on each side) if necessary.

As I already replied on this topic, this will not work on hosts
which support a wide range of supplies.  If you send an OP_COND
command with bits set outside the MMC cards allowable range, they
go gaga.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core

Re: [PATCH 3/3] MMC compatibility fix - OCR mask

[Pierre Ossman]

Russell King wrote:

>On Sat, Sep 18, 2004 at 12:00:16PM +0200, Pierre Ossman wrote:
>  
>
>>This patch avoids using a emtpy OCR mask for the initial power up. Since 
>>some cards do not like a one bit-mask a routine has been added which 
>>grows the mask to three bits (one extra bit on each side) if necessary.
>>    
>>
>
>As I already replied on this topic, this will not work on hosts
>which support a wide range of supplies.  If you send an OP_COND
>command with bits set outside the MMC cards allowable range, they
>go gaga.
>
>  
>
Sorry, my bad. I was reviewing the previous discussion about this in an 
attempt to find a solution. Completely missed that case. Please 
disregard this patch then.

The problem still remains though. Do you know what the wide range 
controller you have send when used with the manufacturer's driver?

Rgds
Pierre

Re: [PATCH 3/3] MMC compatibility fix - OCR mask

[Russell King]

On Sat, Sep 18, 2004 at 01:06:21PM +0200, Pierre Ossman wrote:
> The problem still remains though. Do you know what the wide range 
> controller you have send when used with the manufacturer's driver?

There isn't a manufacturers driver for it.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core

Re: [PATCH 3/3] MMC compatibility fix - OCR mask

[Pierre Ossman]

Russell King wrote:

>On Sat, Sep 18, 2004 at 01:06:21PM +0200, Pierre Ossman wrote:
>  
>
>>The problem still remains though. Do you know what the wide range 
>>controller you have send when used with the manufacturer's driver?
>>    
>>
>
>There isn't a manufacturers driver for it.
>
>  
>
Since I'm a bit keen on actually being able to read the cards I already 
own I have another suggestion. Start out using a zero OCR. If no card 
responds using this we try again using the bit mask created in this 
patch. That would get compliant cards using the first go and the rest 
using the second. If someone tries to combine faulty cards with good 
ones on the same bus the faulty ones will of course not work but at 
least people have the chance of getting them to work when inserted by 
themselves.

Does this sound like a solution that would work? I'd be happy to write 
the code and test it with the cards I have at my disposal.

Rgds
Pierre