If DCD supports queuing of stall requests then USB MSC delay work-around is not necessary

4 files changed, 30 insertions, 0 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 2e3b67ecb..5f7accac9 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -7014,4 +7014,8 @@
 	* include/nuttx/i2c.h:  More typo fixes from Vijay Kumar (2014-3-19).
 	* arch/Kconfig and *_assert.h:  Add a configuration option to enable
 	  dumping of the USB trace buffer on assertion (2014-3-19).
+	* drivers/usbdev/Kconfig, arch/arm/src/sam34/Kconfig, and
+	  drivers/usbdev/usbmsc_scsi.c:  If DCD can support queuing of stall
+	  requests, then the USB MSC stall work around delays are not necessary
+	  (2014-3-20).
 
diff --git a/nuttx/TODO b/nuttx/TODO
index 84b6e8030..762e172d4 100644
--- a/nuttx/TODO
+++ b/nuttx/TODO
@@ -947,6 +947,15 @@ o USB (drivers/usbdev, drivers/usbhost)
   Description: There is a workaround for a bug in drivers/usbdev/usbdev_storage.c.
                that involves delays.  This needs to be redesigned to eliminate these
                delays.  See logic conditioned on CONFIG_USBMSC_RACEWAR.
+
+               If queuing of stall requests is supported by DCD then this workaround
+               is not required.  In this case, (1) the stall is not sent until all
+               write requests preceding the stall request are sent, (2) the stall is
+               sent, and then after the stall is cleared, (3) all write requests
+               queued after the stall are sent.
+
+               See, for example, the queuing of pending stall requests in the SAM3/4
+               UDP driver at arch/arm/src/sam34/sam_udp.c.
   Status:      Open
   Priority:    Medium
 
diff --git a/nuttx/arch/arm/src/sam34/Kconfig b/nuttx/arch/arm/src/sam34/Kconfig
index 2c244a858..16aa5bc05 100644
--- a/nuttx/arch/arm/src/sam34/Kconfig
+++ b/nuttx/arch/arm/src/sam34/Kconfig
@@ -561,6 +561,7 @@ config SAM34_UDP
 	bool "USB Device Full Speed (UDP)"
 	default n
 	depends on ARCH_CHIP_SAM4S || ARCH_CHIP_SAM4E
+	select ARCH_USBDEV_STALLQUEUE
 
 config SAM34_UDPHS
 	bool "USB Device High Speed (UDPHS)"
diff --git a/nuttx/drivers/usbdev/Kconfig b/nuttx/drivers/usbdev/Kconfig
index f512bd4a7..8da9d9e35 100644
--- a/nuttx/drivers/usbdev/Kconfig
+++ b/nuttx/drivers/usbdev/Kconfig
@@ -72,6 +72,22 @@ bool "Board DMA Allocation Hooks"
 		memory of the specified size; usbdev_dma_free() is the corresponding
 		function that will be called to free the DMA-capable memory.
 
+config ARCH_USBDEV_STALLQUEUE
+	bool
+	default n
+	---help---
+		This option is set by the USB device controller driver (DCD)
+		selection.  These selection means that the DCD can support
+		queuing of stall requests.  By this, it is meant that, (1) the
+		stall is not sent until all write requests preceding the stall
+		request are sent, (2) the stall is sent, and then after the
+		stall is cleared, (3) all write requests queued after the stall
+		are sent.
+
+		If the driver does not support this feature, that the class drivers
+		will enable some hokey and inefficient delay logic to workaround
+		the lack of queuing.
+
 config USBDEV_TRACE
 	bool "Enable USB tracing for debug"
 	default n