From 9befa7bd6686042f10b931f8fe55fdd5d844a40b Mon Sep 17 00:00:00 2001 From: Vasily Khoruzhick Date: Thu, 24 Sep 2009 22:17:47 +0300 Subject: [PATCH v2 1/5] s3c2410_udc: 2440 dual packet workaround This is a patch that seems to make the USB hangs on the S3C2440 go away. At least a good amount of ping torture didn't make them come back so far. The issue is that, if there are several back-to-back packets, sometimes no interrupt is generated for one of them. This seems to be caused by the mysterious dual packet mode, which the USB hardware enters automatically if the endpoint size is half that of the FIFO. (On the 2440, this is the normal situation for bulk data endpoints.) There is also a timing factor in this. I think what happens is that the USB hardware automatically sends an acknowledgement if there is only one packet in the FIFO (the FIFO has space for two). If another packet arrives before the host has retrieved and acknowledged the previous one, no interrupt is generated for that second one. However, there may be an indication. There is one undocumented bit (none of the 244x manuals document it), OUT_CRS1_REG[1], that seems to be set suspiciously often when this condition occurs. There is also CLR_DATA_TOGGLE, OUT_CRS1_REG[7], which may have a function related to this. (The Samsung manual is rather terse on that, as usual.) This needs to be examined further. For now, the patch seems to do the trick. Signed-off-by: Vasily Khoruzhick --- drivers/usb/gadget/s3c2410_udc.c | 16 +++++++++++++++- 1 files changed, 15 insertions(+), 1 deletions(-) diff --git a/drivers/usb/gadget/s3c2410_udc.c b/drivers/usb/gadget/s3c2410_udc.c index a9b452f..5749847 100644 --- a/drivers/usb/gadget/s3c2410_udc.c +++ b/drivers/usb/gadget/s3c2410_udc.c @@ -898,7 +898,7 @@ static irqreturn_t s3c2410_udc_irq(int dummy, void *_dev) int pwr_reg; int ep0csr; int i; - u32 idx; + u32 idx, idx2; unsigned long flags; spin_lock_irqsave(&dev->lock, flags); @@ -1013,6 +1013,20 @@ static irqreturn_t s3c2410_udc_irq(int dummy, void *_dev) } } + /* what else causes this interrupt? a receive! who is it? */ + if (!usb_status && !usbd_status && !pwr_reg && !ep0csr) { + for (i = 1; i < S3C2410_ENDPOINTS; i++) { + idx2 = udc_read(S3C2410_UDC_INDEX_REG); + udc_write(i, S3C2410_UDC_INDEX_REG); + + if (udc_read(S3C2410_UDC_OUT_CSR1_REG) & 0x1) + s3c2410_udc_handle_ep(&dev->ep[i]); + + /* restore index */ + udc_write(idx2, S3C2410_UDC_INDEX_REG); + } + } + dprintk(DEBUG_VERBOSE, "irq: %d s3c2410_udc_done.\n", IRQ_USBD); /* Restore old index */ -- 1.6.5.rc1