target/linux/s3c24xx/patches-2.6.24/1027-s3c2410_udc-2440_dual_packet-workaround.patch.patch

   1 From d8310bb7e4ee4a9f3433a9a1e0e87567337299cb Mon Sep 17 00:00:00 2001
   2 From: mokopatches <mokopatches@openmoko.org>
   3 Date: Fri, 4 Apr 2008 11:33:55 +0100
   4 Subject: [PATCH] s3c2410_udc-2440_dual_packet-workaround.patch
   5  This is a patch that seems to make the USB hangs on the S3C2440 go away. At
   6  least a good amount of ping torture didn't make them come back so far.
   7
   8 The issue is that, if there are several back-to-back packets,
   9 sometimes no interrupt is generated for one of them. This
  10 seems to be caused by the mysterious dual packet mode, which
  11 the USB hardware enters automatically if the endpoint size is
  12 half that of the FIFO. (On the 2440, this is the normal
  13 situation for bulk data endpoints.)
  14
  15 There is also a timing factor in this. I think what happens is
  16 that the USB hardware automatically sends an acknowledgement
  17 if there is only one packet in the FIFO (the FIFO has space
  18 for two). If another packet arrives before the host has
  19 retrieved and acknowledged the previous one, no interrupt is
  20 generated for that second one.
  21
  22 However, there may be an indication. There is one undocumented
  23 bit (none of the 244x manuals document it), OUT_CRS1_REG[1],
  24 that seems to be set suspiciously often when this condition
  25 occurs. There is also CLR_DATA_TOGGLE, OUT_CRS1_REG[7], which
  26 may have a function related to this. (The Samsung manual is
  27 rather terse on that, as usual.)
  28
  29 This needs to be examined further. For now, the patch seems to do the
  30 trick.
  31
  32 Note that this is not a clean solution by any means, because we
  33 might potentially get stuck in that interrupt for quite a while.
  34 ---
  35  drivers/usb/gadget/s3c2410_udc.c |    3 +++
  36  1 files changed, 3 insertions(+), 0 deletions(-)
  37
  38 diff --git a/drivers/usb/gadget/s3c2410_udc.c b/drivers/usb/gadget/s3c2410_udc.c
  39 index 4ce050c..d4a17af 100644
  40 --- a/drivers/usb/gadget/s3c2410_udc.c
  41 +++ b/drivers/usb/gadget/s3c2410_udc.c
  42 @@ -845,6 +845,7 @@ static void s3c2410_udc_handle_ep(struct s3c2410_ep *ep)
  43         u32                     ep_csr1;
  44         u32                     idx;
  45
  46 +handle_ep_again:
  47         if (likely (!list_empty(&ep->queue)))
  48                 req = list_entry(ep->queue.next,
  49                                 struct s3c2410_request, queue);
  50 @@ -884,6 +885,8 @@ static void s3c2410_udc_handle_ep(struct s3c2410_ep *ep)
  51
  52                 if ((ep_csr1 & S3C2410_UDC_OCSR1_PKTRDY) && req) {
  53                         s3c2410_udc_read_fifo(ep,req);
  54 +                       if (s3c2410_udc_fifo_count_out())
  55 +                               goto handle_ep_again;
  56                 }
  57         }
  58  }
  59 --
  60 1.5.6.5
  61