Re: dvb usb issues since kernel 4.9

From: Mauro Carvalho Chehab
Date: Fri Jan 26 2018 - 09:17:56 EST


Hi Alan,

Em Mon, 8 Jan 2018 14:15:35 -0500 (EST)
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> escreveu:

> On Mon, 8 Jan 2018, Linus Torvalds wrote:
>
> > Can somebody tell which softirq it is that dvb/usb cares about?
>
> I don't know about the DVB part. The USB part is a little difficult to
> analyze, mostly because the bug reports I've seen are mostly from
> people running non-vanilla kernels.

I suspect that the main reason for people not using non-vanilla Kernels
is that, among other bugs, the dwc2 upstream driver has serious troubles
handling ISOCH traffic.

Using Kernel 4.15-rc7 from this git tree:
https://git.linuxtv.org/mchehab/experimental.git/log/?h=softirq_fixup

(e. g. with the softirq bug partially reverted with Linux patch, and
the DWC2 deferred probe fixed)

With a PCTV 461e device, with uses em28xx driver + Montage frontend
(with is the same used on dvbsky hardware - except for em28xx).

This device doesn't support bulk for DVB, just ISOCH. The drivers work
fine on x86.

Using a test signal at the bit rate of 56698,4 Kbits/s, that's what
happens, when capturing less than one second of data:

$ dvbv5-zap -c ~/dvb_channel.conf "tv brasil" -l universal -X 100 -m -t2dvbv5-zap -c ~/dvb_channel.conf "tv brasil" -l universal -X 100 -m -t2
Using LNBf UNIVERSAL
Universal, Europe
Freqs : 10800 to 11800 MHz, LO: 9750 MHz
Freqs : 11600 to 12700 MHz, LO: 10600 MHz
using demux 'dvb0.demux0'
reading channels from file '/home/mchehab/dvb_channel.conf'
tuning to 11468000 Hz
(0x00) Signal= -33.90dBm
Lock (0x1f) Signal= -33.90dBm C/N= 30.28dB postBER= 2.33x10^-6
dvb_dev_set_bufsize: buffer set to 6160384
dvb_set_pesfilter to 0x2000
354.08s: Starting capture
354.73s: only read 59220 bytes
354.73s: Stopping capture

[ 354.000827] dwc2 3f980000.usb: DWC OTG HCD EP DISABLE: bEndpointAddress=0x84, ep->hcpriv=116f41b2
[ 354.000859] dwc2 3f980000.usb: DWC OTG HCD EP RESET: bEndpointAddress=0x84
[ 354.010744] dwc2 3f980000.usb: --Host Channel 5 Interrupt: Frame Overrun--
... (hundreds of thousands of Frame Overrun messages)
[ 354.660857] dwc2 3f980000.usb: --Host Channel 5 Interrupt: Frame Overrun--
[ 354.660935] dwc2 3f980000.usb: DWC OTG HCD URB Dequeue
[ 354.660959] dwc2 3f980000.usb: Called usb_hcd_giveback_urb()
[ 354.660966] dwc2 3f980000.usb: urb->status = 0
[ 354.660992] dwc2 3f980000.usb: DWC OTG HCD URB Dequeue
[ 354.661001] dwc2 3f980000.usb: Called usb_hcd_giveback_urb()
[ 354.661008] dwc2 3f980000.usb: urb->status = 0
[ 354.661054] dwc2 3f980000.usb: DWC OTG HCD URB Dequeue
[ 354.661065] dwc2 3f980000.usb: Called usb_hcd_giveback_urb()
[ 354.661072] dwc2 3f980000.usb: urb->status = 0
[ 354.661107] dwc2 3f980000.usb: DWC OTG HCD URB Dequeue
[ 354.661120] dwc2 3f980000.usb: Called usb_hcd_giveback_urb()
[ 354.661127] dwc2 3f980000.usb: urb->status = 0
[ 354.661146] dwc2 3f980000.usb: DWC OTG HCD URB Dequeue
[ 354.661158] dwc2 3f980000.usb: Called usb_hcd_giveback_urb()
[ 354.661165] dwc2 3f980000.usb: urb->status = 0

Kernel was compiled with:

CONFIG_USB_DWC2=y
CONFIG_USB_DWC2_HOST=y
# CONFIG_USB_DWC2_PERIPHERAL is not set
# CONFIG_USB_DWC2_DUAL_ROLE is not set
# CONFIG_USB_DWC2_PCI is not set
CONFIG_USB_DWC2_DEBUG=y
# CONFIG_USB_DWC2_VERBOSE is not set
# CONFIG_USB_DWC2_TRACK_MISSED_SOFS is not set
CONFIG_USB_DWC2_DEBUG_PERIODIC=y

As reference, that's the output of lsusb for the PCTV usb hardware:

$ lsusb -v -d 2013:0258

Bus 001 Device 005: ID 2013:0258 PCTV Systems
Couldn't open device, some information will be missing
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x2013 PCTV Systems
idProduct 0x0258
bcdDevice 1.00
iManufacturer 3
iProduct 1
iSerial 2
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 41
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x84 EP 4 IN
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x0000 1x 0 bytes
bInterval 1
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x84 EP 4 IN
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x03ac 1x 940 bytes
bInterval 1

Cheers,
Mauro