Hello
2016-12-06 13:56 GMT+01:00 Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>:
> Em Mon, 5 Dec 2016 22:06:59 +0100
> Marcel Hasler <mahasler@xxxxxxxxx> escreveu:
>
>> Hello
>>
>> 2016-12-05 16:38 GMT+01:00 Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>:
>> > On 5 December 2016 at 09:12, Mauro Carvalho Chehab
>> > <mchehab@xxxxxxxxxxxxxxxx> wrote:
>> >> Em Sun, 4 Dec 2016 15:25:25 -0300
>> >> Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> escreveu:
>> >>
>> >>> On 4 December 2016 at 10:01, Marcel Hasler <mahasler@xxxxxxxxx> wrote:
>> >>> > Hello
>> >>> >
>> >>> > 2016-12-03 21:46 GMT+01:00 Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>:
>> >>> >> On 2 December 2016 at 08:05, Mauro Carvalho Chehab
>> >>> >> <mchehab@xxxxxxxxxxxxxxxx> wrote:
>> >>> >>> Em Sun, 27 Nov 2016 12:11:48 +0100
>> >>> >>> Marcel Hasler <mahasler@xxxxxxxxx> escreveu:
>> >>> >>>
>> >>> >>>> Allow setting a custom record gain for the internal AC97 codec (if available). This can be
>> >>> >>>> a value between 0 and 15, 8 is the default and should be suitable for most users. The Windows
>> >>> >>>> driver also sets this to 8 without any possibility for changing it.
>> >>> >>>
>> >>> >>> The problem of removing the mixer is that you need this kind of
>> >>> >>> crap to setup the volumes on a non-standard way.
>> >>> >>>
>> >>> >>
>> >>> >> Right, that's a good point.
>> >>> >>
>> >>> >>> NACK.
>> >>> >>>
>> >>> >>> Instead, keep the alsa mixer. The way other drivers do (for example,
>> >>> >>> em28xx) is that they configure the mixer when an input is selected,
>> >>> >>> increasing the volume of the active audio channel to 100% and muting
>> >>> >>> the other audio channels. Yet, as the alsa mixer is exported, users
>> >>> >>> can change the mixer settings in runtime using some alsa (or pa)
>> >>> >>> mixer application.
>> >>> >>>
>> >>> >>
>> >>> >> Yeah, the AC97 mixer we are currently leveraging
>> >>> >> exposes many controls that have no meaning in this device,
>> >>> >> so removing that still looks like an improvement.
>> >>> >>
>> >>> >> I guess the proper way is creating our own mixer
>> >>> >> (not using snd_ac97_mixer) exposing only the record
>> >>> >> gain knob.
>> >>> >>
>> >>> >> Marcel, what do you think?
>> >>> >> --
>> >>> >> Ezequiel García, VanguardiaSur
>> >>> >> www.vanguardiasur.com.ar
>> >>> >
>> >>> > As I have written before, the recording gain isn't actually meant to
>> >>> > be changed by the user. In the official Windows driver this value is
>> >>> > hard-coded to 8 and cannot be changed in any way. And there really is
>> >>> > no good reason why anyone should need to mess with it in the first
>> >>> > place. The default value will give the best results in pretty much all
>> >>> > cases and produces approximately the same volume as the internal 8-bit
>> >>> > ADC whose gain cannot be changed at all, not even by a driver.
>> >>> >
>> >>> > I had considered writing a mixer but chose not to. If the gain setting
>> >>> > is openly exposed to mixer applications, how do you tell the users
>> >>> > that the value set by the driver already is the optimal and
>> >>> > recommended value and that they shouldn't mess with the controls
>> >>> > unless they really have to? By having a module parameter, this setting
>> >>> > is practically hidden from the normal user but still is available to
>> >>> > power-users if they think they really need it. In the end it's really
>> >>> > just a compromise between hiding it completely and exposing it openly.
>> >>> > Also, this way the driver guarantees reproducible results, since
>> >>> > there's no need to remember the positions of any volume sliders.
>> >>> >
>> >>>
>> >>> Hm, right. I've never changed the record gain, and it's true that it
>> >>> doens't really improve the volume. So, I would be OK with having
>> >>> a module parameter.
>> >>>
>> >>> On the other side, we are exposing it currently, through the "Capture"
>> >>> mixer control:
>> >>>
>> >>> Simple mixer control 'Capture',0
>> >>> Capabilities: cvolume cswitch cswitch-joined
>> >>> Capture channels: Front Left - Front Right
>> >>> Limits: Capture 0 - 15
>> >>> Front Left: Capture 10 [67%] [15.00dB] [on]
>> >>> Front Right: Capture 8 [53%] [12.00dB] [on]
>> >>>
>> >>> So, it would be user-friendly to keep the user interface and continue
>> >>> to expose the same knob - even if the default is the optimal, etc.
>> >>>
>> >>> To be completely honest, I don't think any user is really relying
>> >>> on any REC_GAIN / Capture setting, and I'm completely OK
>> >>> with having a mixer control or a module parameter. It doesn't matter.
>> >>
>> >> If you're positive that *all* stk1160 use the ac97 mixer the
>> >> same way, and that there's no sense on having a mixer for it,
>> >> then it would be ok to remove it.
>> >>
>> >
>> > Let's remove it then!
>> >
>> >> In such case, then why you need a modprobe parameter to allow
>> >> setting the record level? If this mixer entry is not used,
>> >> just set it to zero and be happy with that.
>> >>
>> >
>> > Let's remove the module param too, then.
>>
>> I'm okay with that.
>>
>> >
>> > Thanks,
>> > --
>> > Ezequiel García, VanguardiaSur
>> > www.vanguardiasur.com.ar
>>
>> I'm willing to prepare one final patchset, provided we can agree on
>> and resolve all issues beforehand.
>>
>> So far the changes would be to remove the module param and to poll
>> STK1160_AC97CTL_0 instead of using a fixed delay. It's probably better
>> to also poll it before writing, although that never caused problems.
>
> Sounds ok. My experience with AC97 on em28xx is that, as new devices
> were added, the delay needed for AC97 varied on some of those new
> devices. That's why checking if AC97 is ready before writing was
> added to its code.
>
>>
>> I'll post some code for review before actually submitting patches.
>> Mauro, is there anything else that you think should be changed? If so,
>> please tell me now. Thanks.
>>
>> Best regards
>> Marcel
>
>
>
> Thanks,
> Mauro
I've implemented the polling function. I'm using it in a slightly
different manner than em28xx, in order to be consistent with the
device's logic as documented in the datasheet. Namely I let the driver
wait after the write instead of before, to make sure
stk1160_write_ac97() only returns once the write has actually
completed. Please tell me if this is okay for you, before I commit and
create the new patchset. Here's the diff:
diff --git a/drivers/media/usb/stk1160/stk1160-ac97.c
b/drivers/media/usb/stk1160/stk1160-ac97.c
diff --git a/drivers/media/usb/stk1160/stk1160-ac97.c
b/drivers/media/usb/stk1160/stk1160-ac97.c
index 95648ac..708792b 100644
--- a/drivers/media/usb/stk1160/stk1160-ac97.c
+++ b/drivers/media/usb/stk1160/stk1160-ac97.c
@@ -23,11 +23,30 @@
*
*/
-#include <linux/module.h>
+#include <linux/delay.h>
#include "stk1160.h"
#include "stk1160-reg.h"
+static int stk1160_ac97_wait_transfer_complete(struct stk1160 *dev)
+{
+ unsigned long timeout = jiffies +
msecs_to_jiffies(STK1160_AC97_TIMEOUT);
+ u8 value;
+
+ /* Wait for AC97 transfer to complete */
+ while (time_is_after_jiffies(timeout)) {
+ stk1160_read_reg(dev, STK1160_AC97CTL_0, &value);
+
+ if (!(value & (STK1160_AC97CTL_0_CR | STK1160_AC97CTL_0_CW)))
+ return 0;
+
+ msleep(1);
+ }
+
+ stk1160_err("AC97 transfer took too long, this should never happen!");
+ return -EBUSY;
+}
+
static void stk1160_write_ac97(struct stk1160 *dev, u16 reg, u16 value)
{
/* Set codec register address */
@@ -37,11 +56,11 @@ static void stk1160_write_ac97(struct stk1160
*dev, u16 reg, u16 value)
stk1160_write_reg(dev, STK1160_AC97_CMD, value & 0xff);
stk1160_write_reg(dev, STK1160_AC97_CMD + 1, (value & 0xff00) >> 8);
- /*
- * Set command write bit to initiate write operation.
- * The bit will be cleared when transfer is done.
- */
+ /* Set command write bit to initiate write operation */
stk1160_write_reg(dev, STK1160_AC97CTL_0, 0x8c);
+
+ /* Wait for command write bit to be cleared */
+ stk1160_ac97_wait_transfer_complete(dev);
}
#ifdef DEBUG
@@ -53,12 +72,14 @@ static u16 stk1160_read_ac97(struct stk1160 *dev, u16 reg)
/* Set codec register address */
stk1160_write_reg(dev, STK1160_AC97_ADDR, reg);
- /*
- * Set command read bit to initiate read operation.
- * The bit will be cleared when transfer is done.
- */
+ /* Set command read bit to initiate read operation */
stk1160_write_reg(dev, STK1160_AC97CTL_0, 0x8b);
+ /* Wait for command read bit to be cleared */
+ if (stk1160_ac97_wait_transfer_complete(dev) < 0) {
+ return 0;
+ }
+
/* Retrieve register value */
stk1160_read_reg(dev, STK1160_AC97_CMD, &vall);
stk1160_read_reg(dev, STK1160_AC97_CMD + 1, &valh);
diff --git a/drivers/media/usb/stk1160/stk1160-reg.h
b/drivers/media/usb/stk1160/stk1160-reg.h
index 296a9e7..7b08a3c 100644
--- a/drivers/media/usb/stk1160/stk1160-reg.h
+++ b/drivers/media/usb/stk1160/stk1160-reg.h
@@ -122,6 +122,8 @@
/* AC97 Audio Control */
#define STK1160_AC97CTL_0 0x500
#define STK1160_AC97CTL_1 0x504
+#define STK1160_AC97CTL_0_CR BIT(1)
+#define STK1160_AC97CTL_0_CW BIT(2)
/* Use [0:6] bits of register 0x504 to set codec command address */
#define STK1160_AC97_ADDR 0x504
diff --git a/drivers/media/usb/stk1160/stk1160.h
b/drivers/media/usb/stk1160/stk1160.h
index e85e12e..acd1c81 100644
--- a/drivers/media/usb/stk1160/stk1160.h
+++ b/drivers/media/usb/stk1160/stk1160.h
@@ -50,6 +50,8 @@
#define STK1160_MAX_INPUT 4
#define STK1160_SVIDEO_INPUT 4
+#define STK1160_AC97_TIMEOUT 50
+
#define STK1160_I2C_TIMEOUT 100
Best regards
Marcel
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
