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SAM4E USP: Re-vamp read request queue handling. Add logic to handle RX overrun errors

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Gregory Nutt 2014-03-26 11:38:47 -06:00
parent 9350b9d4d0
commit 698a4c2cd2
1 changed files with 47 additions and 13 deletions
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configs/sam4e-ek/README.txt
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@ -674,9 +674,8 @@ USB Full-Speed Device
2014-3-25: Marginally functional. Very slow to come up. USB analyzer
shows several resets before the host decides that it is
happy with the device. There are no obvious errors in the
USB data capture.
2014-3-25: There also seem to be issues about writing files. This
needs more investigation.
USB data capture. Testing is insufficient. This needs to
be revisited.
CDC/ACM Serial Device Class
---------------------------
@ -714,6 +713,38 @@ USB Full-Speed Device
than requires that you first install a serial driver (a .inf file). There
are example .inf files for NuttX in the nuttx/configs/spark directories.
3. There is hand-shaking to pace incoming serial data. As a result, you may
experience data loss due to RX overrun errors. The overrun errors occur
when more data is received than can be buffered in memory on the target.
At present, the only workaround is to increase the amount of buffering
in the target. That allow the target to accept short bursts of larger
volumes of data (but would still fail on sustained, high speed incoming
data. The following configuration options can be changed to increase
the buffering.
1. RX buffer size. All incoming data is buffered by the serial driver
until it can be read by the application. The default size of this
RX buffer is only 256 but can be increased as you see fit:
CONFIG_CDCACM_RXBUFSIZE=256 : Default RX buffer size is only 256 bytes
2. Upstream from the RX buffers are USB read request buffers. Each
buffer is the maximum size of one USB packet (64 byte) and that cannot
really be changed. But if you want to increase this upstream buffering
capability, you can increase the number of available read requests.
The default is four, providing an additional buffering capability of
of 4*64=256 bytes.
Each read request receives data from USB, copies the data into the
serial RX buffer, and then is available to receive more data. This
recycling of read requests stalls as soon as the serial RX buffer is
full. Data loss occurs when there are no available read requests to
accept the next packet from the host. So increasing the number of
read requests can also help to minimize RX overrun:
CONFIG_CDCACM_NRDREQS=4 : Default is only 4 read requests
STATUS:
2013-2-23: Checks out OK. See discussion of the usbnsh configuration
@ -1174,15 +1205,13 @@ Configurations
above under "USB Full-Speed Device."
STATUS:
2014-3-21: USB support is under development and USB MSC support is
only partially functional. Additional test and integration
is required.
2014-3-21: USB support is partially functional. Additional test and
integration is required. See STATUS in the "USB Full-Speed
Device" for further information
2014-3-22: USB seems to work properly (there are not obvious errors
in a USB bus capture. However, the AT25 does not mount
on either the Linux or Windows host. Since there are no
USB errors, this could only be an issue with the USB MSC
protocol (not likely) or with the FAT format on the AT25
serial FLASH (likely).
in a USB bus capture. However, as of this data the AT25
does not mount on either the Linux or Windows host. This
needs to be retested.
7. This configuration can be used to verify the touchscreen on on the
SAM4E-EK LCD. See the instructions above in the paragraph entitled
@ -1201,7 +1230,8 @@ Configurations
to data overrun problems. The current HSMCI driver
supports DMA via the DMAC. However, the data sheet
only discusses PDC-based HSMCI DMA (although there is
a DMA channel interface definition for HSMCI).
a DMA channel interface definition for HSMCI). So
this is effort is dead-in-the-water for now.
usbnsh:
@ -1224,7 +1254,7 @@ Configurations
entitled "USB Full-Speed Device",
b. The CDC/ACM serial class is enabled as described in the paragraph
"CDC/ACM Serial Device Class"
"CDC/ACM Serial Device Class".
c. The serial console is disabled:
@ -1241,6 +1271,10 @@ Configurations
d. Support for debug output on UART0 is provided as described in the
next note.
3. If you send large amounts of data to the target, you may see data
loss due to RX overrun errors. See the NOTES in the section entitle
"CDC/ACM Serial Device Class" for some possible work-arounds.
3. This configuration does have UART0 output enabled and set up as
the system logging device: