ALSA: usb-audio: Fix the mixer control range limiting issue

Message ID 20190821100225.9254-1-srinivas.kandagatla@linaro.org
State New
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Series
  • ALSA: usb-audio: Fix the mixer control range limiting issue
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Commit Message

Srinivas Kandagatla Aug. 21, 2019, 10:02 a.m.
From: Deepa Madiregama <dmadireg@codeaurora.org>


- mixer_ctl_set() function is limiting the volume level
  to particular range. This results in incorrect initial
  volume setting for that device.
- In USB mixer while calculating the dBmin/dBmax values
  resolution factor is hardcoded to 256 which results in
  populating the wrong values for dBmin/dBmax.
- Fix is to use appropriate resolution factor while
  calculating the dBmin/dBmax values.

Signed-off-by: Deepa Madiregama <dmadireg@codeaurora.org>

Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>

Signed-off-by: Meng Wang <mwang@codeaurora.org>

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

---
 sound/usb/mixer.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

-- 
2.21.0

Comments

Takashi Iwai Aug. 21, 2019, 5:05 p.m. | #1
On Wed, 21 Aug 2019 12:02:25 +0200,
Srinivas Kandagatla wrote:
> 

> From: Deepa Madiregama <dmadireg@codeaurora.org>

> 

> - mixer_ctl_set() function is limiting the volume level

>   to particular range. This results in incorrect initial

>   volume setting for that device.

> - In USB mixer while calculating the dBmin/dBmax values

>   resolution factor is hardcoded to 256 which results in

>   populating the wrong values for dBmin/dBmax.

> - Fix is to use appropriate resolution factor while

>   calculating the dBmin/dBmax values.


This change doesn't sound right.  Basically the values returned from
USB-audio FEATURE UNIT or MIXER UNIT are always in 1/256 dB unit, per 
definition.  And we pass dB min/max to user-space as TLV_DB_MINMAX(),
i.e. TLV points just both min and max, no matter what scale is.  I
believe that the current code is correct in this regard.

So, it's either a firmware bug that gives the wrong values back, or
the case we still don't cover, e.g. multiple RANGE values for
UAC2/UAC3.

Please check what exactly doesn't work as expected.  Which value is
returned from the USB-audio device and what is wrongly interpreted.


thanks,

Takashi


> Signed-off-by: Deepa Madiregama <dmadireg@codeaurora.org>

> Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>

> Signed-off-by: Meng Wang <mwang@codeaurora.org>

> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

> ---

>  sound/usb/mixer.c | 6 ++++--

>  1 file changed, 4 insertions(+), 2 deletions(-)

> 

> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c

> index 5070a6a76ab3..a67448327d07 100644

> --- a/sound/usb/mixer.c

> +++ b/sound/usb/mixer.c

> @@ -1248,8 +1248,10 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,

>  	/* USB descriptions contain the dB scale in 1/256 dB unit

>  	 * while ALSA TLV contains in 1/100 dB unit

>  	 */

> -	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;

> -	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;

> +	cval->dBmin =

> +		(convert_signed_value(cval, cval->min) * 100) / (cval->res);

> +	cval->dBmax =

> +		(convert_signed_value(cval, cval->max) * 100) / (cval->res);

>  	if (cval->dBmin > cval->dBmax) {

>  		/* something is wrong; assume it's either from/to 0dB */

>  		if (cval->dBmin < 0)

> -- 

> 2.21.0

>
Srinivas Kandagatla Aug. 22, 2019, 11:39 a.m. | #2
On 21/08/2019 18:05, Takashi Iwai wrote:
> On Wed, 21 Aug 2019 12:02:25 +0200,

> Srinivas Kandagatla wrote:

>>

>> From: Deepa Madiregama <dmadireg@codeaurora.org>

>>

>> - mixer_ctl_set() function is limiting the volume level

>>    to particular range. This results in incorrect initial

>>    volume setting for that device.

>> - In USB mixer while calculating the dBmin/dBmax values

>>    resolution factor is hardcoded to 256 which results in

>>    populating the wrong values for dBmin/dBmax.

>> - Fix is to use appropriate resolution factor while

>>    calculating the dBmin/dBmax values.

> 

> This change doesn't sound right.  Basically the values returned from

> USB-audio FEATURE UNIT or MIXER UNIT are always in 1/256 dB unit, per

> definition.  And we pass dB min/max to user-space as TLV_DB_MINMAX(),

> i.e. TLV points just both min and max, no matter what scale is.  I

> believe that the current code is correct in this regard.

> 

> So, it's either a firmware bug that gives the wrong values back, or

> the case we still don't cover, e.g. multiple RANGE values for

> UAC2/UAC3.

> 

> Please check what exactly doesn't work as expected.  Which value is

> returned from the USB-audio device and what is wrongly interpreted.

> 


Thanks for the detailed review.

I see https://www.usb.org/sites/default/files/audio10.pdf clearly 
specifies Mixer unit is always 1/256dB units.

This patch has been carried in Qcom downstream kernels for past many 
years to fix very low Initial volume setting on some USB headsets like 
Logitech S-150 USB Speakers and Nokia HS-82 USB headset.

Its highly likely that its a firmware bug!, but I will try to get it 
retested on latest kernel and collect some logs!

Thanks,
srini


> 

> thanks,

> 

> Takashi

> 

> 

>> Signed-off-by: Deepa Madiregama <dmadireg@codeaurora.org>

>> Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>

>> Signed-off-by: Meng Wang <mwang@codeaurora.org>

>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

>> ---

>>   sound/usb/mixer.c | 6 ++++--

>>   1 file changed, 4 insertions(+), 2 deletions(-)

>>

>> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c

>> index 5070a6a76ab3..a67448327d07 100644

>> --- a/sound/usb/mixer.c

>> +++ b/sound/usb/mixer.c

>> @@ -1248,8 +1248,10 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,

>>   	/* USB descriptions contain the dB scale in 1/256 dB unit

>>   	 * while ALSA TLV contains in 1/100 dB unit

>>   	 */

>> -	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;

>> -	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;

>> +	cval->dBmin =

>> +		(convert_signed_value(cval, cval->min) * 100) / (cval->res);

>> +	cval->dBmax =

>> +		(convert_signed_value(cval, cval->max) * 100) / (cval->res);

>>   	if (cval->dBmin > cval->dBmax) {

>>   		/* something is wrong; assume it's either from/to 0dB */

>>   		if (cval->dBmin < 0)

>> -- 

>> 2.21.0

>>

Patch

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 5070a6a76ab3..a67448327d07 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1248,8 +1248,10 @@  static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 	/* USB descriptions contain the dB scale in 1/256 dB unit
 	 * while ALSA TLV contains in 1/100 dB unit
 	 */
-	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
-	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
+	cval->dBmin =
+		(convert_signed_value(cval, cval->min) * 100) / (cval->res);
+	cval->dBmax =
+		(convert_signed_value(cval, cval->max) * 100) / (cval->res);
 	if (cval->dBmin > cval->dBmax) {
 		/* something is wrong; assume it's either from/to 0dB */
 		if (cval->dBmin < 0)