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62 lines
2.3 KiB
Diff
62 lines
2.3 KiB
Diff
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From 5207363cc9d50f99a2ad490eff5efa913b1c10ba Mon Sep 17 00:00:00 2001
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From: mokopatches <mokopatches@openmoko.org>
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Date: Wed, 16 Jul 2008 14:44:50 +0100
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Subject: [PATCH] s3c2410_udc-2440_dual_packet-workaround.patch
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This is a patch that seems to make the USB hangs on the S3C2440 go away. At
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least a good amount of ping torture didn't make them come back so far.
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The issue is that, if there are several back-to-back packets,
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sometimes no interrupt is generated for one of them. This
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seems to be caused by the mysterious dual packet mode, which
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the USB hardware enters automatically if the endpoint size is
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half that of the FIFO. (On the 2440, this is the normal
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situation for bulk data endpoints.)
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There is also a timing factor in this. I think what happens is
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that the USB hardware automatically sends an acknowledgement
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if there is only one packet in the FIFO (the FIFO has space
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for two). If another packet arrives before the host has
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retrieved and acknowledged the previous one, no interrupt is
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generated for that second one.
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However, there may be an indication. There is one undocumented
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bit (none of the 244x manuals document it), OUT_CRS1_REG[1],
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that seems to be set suspiciously often when this condition
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occurs. There is also CLR_DATA_TOGGLE, OUT_CRS1_REG[7], which
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may have a function related to this. (The Samsung manual is
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rather terse on that, as usual.)
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This needs to be examined further. For now, the patch seems to do the
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trick.
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Note that this is not a clean solution by any means, because we
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might potentially get stuck in that interrupt for quite a while.
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---
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drivers/usb/gadget/s3c2410_udc.c | 3 +++
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1 files changed, 3 insertions(+), 0 deletions(-)
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diff --git a/drivers/usb/gadget/s3c2410_udc.c b/drivers/usb/gadget/s3c2410_udc.c
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index 6b1ef48..c1a4379 100644
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--- a/drivers/usb/gadget/s3c2410_udc.c
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+++ b/drivers/usb/gadget/s3c2410_udc.c
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@@ -845,6 +845,7 @@ static void s3c2410_udc_handle_ep(struct s3c2410_ep *ep)
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u32 ep_csr1;
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u32 idx;
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+handle_ep_again:
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if (likely (!list_empty(&ep->queue)))
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req = list_entry(ep->queue.next,
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struct s3c2410_request, queue);
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@@ -884,6 +885,8 @@ static void s3c2410_udc_handle_ep(struct s3c2410_ep *ep)
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if ((ep_csr1 & S3C2410_UDC_OCSR1_PKTRDY) && req) {
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s3c2410_udc_read_fifo(ep,req);
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+ if (s3c2410_udc_fifo_count_out())
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+ goto handle_ep_again;
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}
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}
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}
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--
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1.5.6.3
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