Hi,
I ran into a problem of "choppy" audio when using a USB codec on a
i.MX53 (with the chipidea driver)
The problem occurs on 4.4.47 but not on an old 3.19
It also does not occur on the latest 4.10.
The codec is :
Bus 001 Device 003: ID 08bb:29c0 Texas Instruments Japan PCM2900C Audio
CODEC
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x08bb Texas Instruments Japan
idProduct 0x29c0 PCM2900C Audio CODEC
bcdDevice 1.00
iManufacturer 1 BurrBrown from Texas Instruments
iProduct 2 USB AUDIO CODEC
iSerial 0
Bisecting between 3.19 and 4.4 narrows it down to this commit:
commit e765bfb73ff711b1d139a4438af9ecedabb07d34
Author: Peter Chen <peter.chen@xxxxxxxxxxxxx>
Date: Thu Jun 18 11:43:34 2015 +0800
usb: chipidea: imx: enable CI_HDRC_SET_NON_ZERO_TTHA
For i.mx platform, set ttctrl.ttha with non-zero value only affects
sitd, and ehci core makes sure the schedule is not full when accepts
new request, so it will not occur the transaction which will acorss
the SoF.
And indeed reverting that fixes the problem on 4.4
I see that this has already been reverted in 4.5 by:
commit 1bc7da87c7410c6990c3251589e3854e64c55af2
Author: Peter Chen <peter.chen@xxxxxxx>
Date: Fri Jan 29 16:47:24 2016 +0800
Revert "usb: chipidea: imx: enable CI_HDRC_SET_NON_ZERO_TTHA"
This reverts commit e765bfb73ff7.
In the most of cases, we only use one transaction per frame and the
frame rate may be high, If the platforms want to support multiple
transactions but less frame rate cases like [1] and [2], it can set
"non-zero-ttctrl-ttha" at dts.
[1] http://www.spinics.net/lists/linux-usb/msg123125.html
[2] http://www.spinics.net/lists/linux-usb/msg118679.html
Signed-off-by: Peter Chen <peter.chen@xxxxxxx>
Which explains why 4.10 is ok.
But, maybe this should be backported to 4.4 (old)stable?
However the revert commit message doesn't really indicate that it is a
bug fix.
The links in the revert commit are describing scenarios involving
multiple codecs, whereas I am only using one.
Anyway, mentionning it here might help someone else googling this problem.
Regards,
Martin
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