Re: PXA27x UDC driver GIT repository

 Hello David,

 I tested your UDC driver on my PXA270-based board (the Colibri analogue) with 
the file-storage gadget on the top and found that it operates well only with 
stall=N option set. When I used the default stall setting (i.e. 'Y') then my 
USB host (x86 PC) reported about the error:

[yur]# dmesg
...
usb 1-2: new full speed USB device using uhci_hcd and address 35
usb 1-2: configuration #1 chosen from 1 choice
scsi34 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 35
usb-storage: waiting for device to settle before scanning
scsi 34:0:0:0: Direct-Access     Linux    File-Stor Gadget 0311 PQ: 0 ANSI: 2
SCSI device sdb: 7862272 512-byte hdwr sectors (4025 MB)
usb 1-2: reset full speed USB device using uhci_hcd and address 35
sdb: Write Protect is off
sdb: Mode Sense: 0f 00 00 00
sdb: assuming drive cache: write through
SCSI device sdb: 7862272 512-byte hdwr sectors (4025 MB)
sdb: Write Protect is off
sdb: Mode Sense: 0f 00 00 00
sdb: assuming drive cache: write through
 sdb:<6>usb 1-2: reset full speed USB device using uhci_hcd and address 35
usb 1-2: reset full speed USB device using uhci_hcd and address 35
usb 1-2: reset full speed USB device using uhci_hcd and address 35
sd 35:0:0:0: SCSI error: return code = 0x00070000
end_request: I/O error, dev sdb, sector 0
Buffer I/O error on device sdb, logical block 0
usb 1-2: reset full speed USB device using uhci_hcd and address 35
usb 1-2: reset full speed USB device using uhci_hcd and address 35
...


 I investigated the problem and found the following reference in the PXA270 
Developers Manual document:
"
 12.6.8.5 Sent STALL and Force STALL
 ...
 Note: Users must clear the SST bit before the USB host controller requests 
more data from IN endpoints or invalid or corrupted data may be sent to the 
host.
 ...
"

 What follows is the patch (also attached) which modifies the pxa27x UDC 
driver according to the note mentioned above. Using this patch I successfully 
run the UDC driver with the file-storage gadget on its top and mounted the 
backing file exported by the gadget on my host PC.

 Perhaps this is not the most effective and elegant way of fixing the bug 
discovered, or  there are some other places in the UDC driver where the 
corresponding fix has to be applied too. What do you think ?

--
 The patch fixes the errors happened on the bus during the bulk transactions
when the pxa27x UDC driver is used together with the file-storage gadget.

 Signed-off-by: Yuri Tikhonov <[email protected]>
--
diff --git a/drivers/usb/gadget/pxa27x_udc.c b/drivers/usb/gadget/pxa27x_udc.c
index f7c0052..672e301 100644
--- a/drivers/usb/gadget/pxa27x_udc.c
+++ b/drivers/usb/gadget/pxa27x_udc.c
@@ -1057,8 +1057,14 @@ static int pxa27x_ep_set_halt(struct usb_ep *_ep, int 
value)
        } else {
                unsigned i;
                for (i = 0; i < 1000; i += 20) {
-                       if (*ep->reg_udccsr & UDCCSR_SST)
+                       if (*ep->reg_udccsr & UDCCSR_SST) {
+                               /* According to UM we must clear the SST bit
+                                * before the USB host controller requests 
more
+                                * data from IN endpoints; do it right now.
+                                */
+                               *ep->reg_udccsr = UDCCSR_SST;
                                break;
+                       }
                        udelay(20);
                }
        }

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 The patch fixes the errors happened on the bus during the bulk transactions
when the pxa27x UDC driver is used together with the file-storage gadget.

 Signed-off-by: Yuri Tikhonov <[email protected]>
--
diff --git a/drivers/usb/gadget/pxa27x_udc.c b/drivers/usb/gadget/pxa27x_udc.c
index f7c0052..672e301 100644
--- a/drivers/usb/gadget/pxa27x_udc.c
+++ b/drivers/usb/gadget/pxa27x_udc.c
@@ -1057,8 +1057,14 @@ static int pxa27x_ep_set_halt(struct usb_ep *_ep, int value)
 	} else {
 		unsigned i;
 		for (i = 0; i < 1000; i += 20) {
-			if (*ep->reg_udccsr & UDCCSR_SST)
+			if (*ep->reg_udccsr & UDCCSR_SST) {
+				/* According to UM we must clear the SST bit
+				 * before the USB host controller requests more
+				 * data from IN endpoints; do it right now.
+				 */
+				*ep->reg_udccsr = UDCCSR_SST;
 				break;
+			}
 			udelay(20);
 		}
 	}