[PATCH v4 0/5] dma: mxs-dma bugfixes and cleanup

[Fabio Estevam]

Hi Markus,

[Also including alsa-devel and some other folks involved with mxs audio]

On Fri, Oct 11, 2013 at 9:12 AM, Markus Pargmann <mpa at pengutronix.de> wrote:
> Hi,
>
> v4 adds another patch to increase sound stability. Patch 3 ("dma: mxs-dma: Fix
> channel reset hardware bug") decreases the number of channel stalls, but after
> hours of repeated playback the bug still appears. The new patch ("dma: mxs: Use
> semaphores for cyclic DMA") replaces reset channel usage with hardware
> semaphore counter mechanism.

How is the bug you are trying to solve manifest and how to reproduce it?

I have been investigating an issue about sound stability on mx28 as well.

The usecase I am doing is:

while true
do
    arecord -D hw:0,1 -d 10 -f S16_LE -r 44100 -c 2 | aplay
    sleep 2
done

(Record 10 seconds, sleep and keep in this loop forever).

The problem I see is that randomly the captured audio becomes
extremely noisy and loud (throughout the whole 10 seconds) and then in
the subsequent loop it becomes normal. This is very random and it
happens at a 1 or 2% failure rate.

I tested your v3, but it did not help to fix this particular issue.

I also tried experimenting with the SAIF IOMUX settings:

index cda19c8..463fa92 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -545,9 +545,9 @@
                         MX28_PAD_SAIF0_BITCLK__SAIF0_BITCLK
                         MX28_PAD_SAIF0_SDATA0__SAIF0_SDATA0
                     >;
-                    fsl,drive-strength = <MXS_DRIVE_12mA>;
+                    fsl,drive-strength = <MXS_DRIVE_4mA>;
                     fsl,voltage = <MXS_VOLTAGE_HIGH>;
-                    fsl,pull-up = <MXS_PULL_ENABLE>;
+                    fsl,pull-up = <MXS_PULL_DISABLE>;
                 };

                 saif0_pins_b: saif0 at 1 {
@@ -557,9 +557,9 @@
                         MX28_PAD_SAIF0_BITCLK__SAIF0_BITCLK
                         MX28_PAD_SAIF0_SDATA0__SAIF0_SDATA0
                     >;
-                    fsl,drive-strength = <MXS_DRIVE_12mA>;
+                    fsl,drive-strength = <MXS_DRIVE_4mA>;
                     fsl,voltage = <MXS_VOLTAGE_HIGH>;
-                    fsl,pull-up = <MXS_PULL_ENABLE>;
+                    fsl,pull-up = <MXS_PULL_DISABLE>;
                 };

                 saif1_pins_a: saif1 at 0 {
@@ -567,9 +567,9 @@
                     fsl,pinmux-ids = <
                         MX28_PAD_SAIF1_SDATA0__SAIF1_SDATA0
                     >;
-                    fsl,drive-strength = <MXS_DRIVE_12mA>;
+                    fsl,drive-strength = <MXS_DRIVE_4mA>;
                     fsl,voltage = <MXS_VOLTAGE_HIGH>;
-                    fsl,pull-up = <MXS_PULL_ENABLE>;
+                    fsl,pull-up = <MXS_PULL_DISABLE>;
                 };

and my tests are showing a much better stability. Not able to get this
problem after several hours.

Regards,

Fabio Estevam