[PATCH] MMC: Select only one voltage bit in OCR response

[PATCH] MMC: Select only one voltage bit in OCR response

[Timo Teras]

The card might go to inactive state (according to specification), if
there are unsupported bits set in the OCR.

Signed-off-by: Timo Teras <timo.teras@solidboot.com>

---

 drivers/mmc/mmc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

8208e380f51ca772e84a0b83098d24aacfa3cc2b
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index acc5365..61bf3fc 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -475,7 +475,7 @@ static u32 mmc_select_voltage(struct mmc
 	if (bit) {
 		bit -= 1;
 
-		ocr = 3 << bit;
+		ocr = 1 << bit;
 
 		host->ios.vdd = bit;
 		mmc_set_ios(host);
-- 
1.2.3.g90cc1

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Russell King]

On Mon, Oct 09, 2006 at 06:00:44PM +0300, Timo Teras wrote:
> The card might go to inactive state (according to specification), if
> there are unsupported bits set in the OCR.

NAK.  This breaks some MMC cards.

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

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Timo Teras]

On Mon, Oct 09, 2006 at 05:53:17PM +0100, Russell King wrote:
> On Mon, Oct 09, 2006 at 06:00:44PM +0300, Timo Teras wrote:
> > The card might go to inactive state (according to specification), if
> > there are unsupported bits set in the OCR.
> 
> NAK.  This breaks some MMC cards.

I see. But if we do send an OCR with an unsupported bit set, the card will
go to inactive state and is unusable. This problem is masked on controllers
with only 3.3V support, but I'm working with a controller supporting several
different voltages.

For example, I have a card giving an OCR reply of 0x0ff80080. The current
code will reply to this with 0x00000180 which is clearly incorrect.

Maybe something like "ocr &= 3 << bit;" would be more approriate?

Cheers,
  Timo

[PATCH] MMC: Do not set unsupported bits in OCR response

[Timo Teras]

The card might go to inactive state (according to specification), if
there are unsupported bits set in the OCR.

Signed-off-by: Timo Teras <timo.teras@solidboot.com>

---

 drivers/mmc/mmc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index ee8863c..c6f3077 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -475,7 +475,7 @@ static u32 mmc_select_voltage(struct mmc
        if (bit) {
                bit -= 1;
 
-               ocr = 3 << bit;
+               ocr &= 3 << bit;
 
                host->ios.vdd = bit;
                mmc_set_ios(host);

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Pierre Ossman]

Timo Teras wrote:
> I see. But if we do send an OCR with an unsupported bit set, the card will
> go to inactive state and is unusable. This problem is masked on controllers
> with only 3.3V support, but I'm working with a controller supporting several
> different voltages.
>
> For example, I have a card giving an OCR reply of 0x0ff80080. The current
> code will reply to this with 0x00000180 which is clearly incorrect.
>
> Maybe something like "ocr &= 3 << bit;" would be more approriate?
>   

Russell? Comments? Do you still have the offending card?

-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org
  OLPC, developer                     http://www.laptop.org

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Pierre Ossman]

(In case you've missed it)

Pierre Ossman wrote:
> Timo Teras wrote:
>> I see. But if we do send an OCR with an unsupported bit set, the card will
>> go to inactive state and is unusable. This problem is masked on controllers
>> with only 3.3V support, but I'm working with a controller supporting several
>> different voltages.
>>
>> For example, I have a card giving an OCR reply of 0x0ff80080. The current
>> code will reply to this with 0x00000180 which is clearly incorrect.
>>
>> Maybe something like "ocr &= 3 << bit;" would be more approriate?
>>   
> 
> Russell? Comments? Do you still have the offending card?
> 

-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Russell King]

On Mon, Oct 16, 2006 at 08:34:20AM +0200, Pierre Ossman wrote:
> Timo Teras wrote:
> > I see. But if we do send an OCR with an unsupported bit set, the card will
> > go to inactive state and is unusable. This problem is masked on controllers
> > with only 3.3V support, but I'm working with a controller supporting several
> > different voltages.
> >
> > For example, I have a card giving an OCR reply of 0x0ff80080. The current
> > code will reply to this with 0x00000180 which is clearly incorrect.
> >
> > Maybe something like "ocr &= 3 << bit;" would be more approriate?
> >   
> 
> Russell? Comments? Do you still have the offending card?

It wasn't my cards, but was reported by several other folk.  I don't think
we can revert on this without breakage.

However, we should probably ensure that we don't end up setting voltage
bits which the cards don't support.  So maybe masking the resulting OCR
value with the received combined OCR would be a good idea?  Such as:

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index ee8863c..45e0598 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -467,23 +467,24 @@ static inline void mmc_delay(unsigned in
  */
 static u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
 {
+	u32 selected_ocr;
 	int bit;
 
-	ocr &= host->ocr_avail;
+	selected_ocr = ocr & host->ocr_avail;
 
-	bit = ffs(ocr);
+	bit = ffs(selected_ocr);
 	if (bit) {
 		bit -= 1;
 
-		ocr = 3 << bit;
+		selected_ocr = 3 << bit;
 
 		host->ios.vdd = bit;
 		mmc_set_ios(host);
 	} else {
-		ocr = 0;
+		selected_ocr = 0;
 	}
 
-	return ocr;
+	return selected_ocr & ocr;
 }
 
 #define UNSTUFF_BITS(resp,start,size)					\


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

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Juha Yrjola]

Russell King wrote:

>>> Maybe something like "ocr &= 3 << bit;" would be more approriate?
>>>   
>> Russell? Comments? Do you still have the offending card?
> 
> It wasn't my cards, but was reported by several other folk.  I don't think
> we can revert on this without breakage.
> 
> However, we should probably ensure that we don't end up setting voltage
> bits which the cards don't support.  So maybe masking the resulting OCR
> value with the received combined OCR would be a good idea?  Such as:

Isn't this exactly what Timo is proposing above?

Cheers,
Juha

> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
> index ee8863c..45e0598 100644
> --- a/drivers/mmc/mmc.c
> +++ b/drivers/mmc/mmc.c
> @@ -467,23 +467,24 @@ static inline void mmc_delay(unsigned in
>   */
>  static u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
>  {
> +	u32 selected_ocr;
>  	int bit;
>  
> -	ocr &= host->ocr_avail;
> +	selected_ocr = ocr & host->ocr_avail;
>  
> -	bit = ffs(ocr);
> +	bit = ffs(selected_ocr);
>  	if (bit) {
>  		bit -= 1;
>  
> -		ocr = 3 << bit;
> +		selected_ocr = 3 << bit;
>  
>  		host->ios.vdd = bit;
>  		mmc_set_ios(host);
>  	} else {
> -		ocr = 0;
> +		selected_ocr = 0;
>  	}
>  
> -	return ocr;
> +	return selected_ocr & ocr;
>  }

Re: [PATCH] MMC: Select only one voltage bit in OCR response

[Pierre Ossman]

Juha Yrjola wrote:
>
> Isn't this exactly what Timo is proposing above?
>

I sure can't see the difference. Timo's patch queued up for -mm.

Rgds

-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org