usb: gadget: musb: fix short isoc packets with inventra dma for pandaboard es

Paul Elder
2018-10-09T06:32:20Z

Handling short packets (length < max packet size) in the Inventra DMA
engine in the MUSB driver causes the MUSB DMA controller to hang. An
example of a problem that is caused by this problem is when streaming
video out of a UVC gadget, only the first video frame is transferred.

For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
set manually by the driver. This was previously done in musb_g_tx
(musb_gadget.c), but incorrectly (all csr flags were cleared, and only
MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY). Fixing that problem allows
some requests to be transferred correctly, but multiple requests were
often put together in one USB packet, and caused problems if the packet
size was not a multiple of 4.

Instead, MUSB_TXCSR_TXPKTRDY is set in dma_controller_irq (musbhsdma.c),
just like host mode transfers, then musb_g_tx forces the packet to be
flushed, by setting MUSB_TXCSR_FLUSHFIFO.

This topic was originally tackled by Nicolas Boichat [0] [1] and is discussed
further at [2] as part of his GSoC project [3].

[0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
[1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
[2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
[3] http://elinux.org/BeagleBoard/GSoC/USBSniffer

I have forward-ported this patch from 2.6.34 to 4.19-rc1.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
---
drivers/usb/musb/musb_gadget.c | 21 ++++++++++++++-------
drivers/usb/musb/musbhsdma.c | 21 +++++++++++----------
2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index eae8b1b1b45b..d3f33f449445 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -479,11 +479,16 @@ void musb_g_tx(struct musb *musb, u8 epnum)
&& (request->actual == request->length))
short_packet = true;

- if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
- (is_dma && (!dma->desired_mode ||
- (request->actual &
- (musb_ep->packet_sz - 1)))))
- short_packet = true;
+ if (is_dma && (musb_dma_inventra(musb) || musb_dma_ux500(musb))) {
+ if (!dma->desired_mode ||
+ request->actual % musb_ep->packet_sz) {
+ musb_dbg(musb, "%s Flushing (FIFO) EP : KPB\n",
+ musb_ep->end_point.name);
+ musb_writew(epio, MUSB_TXCSR,
+ csr | MUSB_TXCSR_FLUSHFIFO);
+ return;
+ }
+ }

if (short_packet) {
/*
@@ -493,8 +498,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
if (csr & MUSB_TXCSR_TXPKTRDY)
return;

- musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
- | MUSB_TXCSR_TXPKTRDY);
+ musb_dbg(musb, "sending zero pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
+ request->zero, request->length, request->actual,
+ dma->desired_mode);
+ musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);
request->zero = 0;
}

diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
index a688f7f87829..e514d4700a6b 100644
--- a/drivers/usb/musb/musbhsdma.c
+++ b/drivers/usb/musb/musbhsdma.c
@@ -346,12 +346,10 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
channel->status = MUSB_DMA_STATUS_FREE;

/* completed */
- if ((devctl & MUSB_DEVCTL_HM)
- && (musb_channel->transmit)
- && ((channel->desired_mode == 0)
- || (channel->actual_len &
- (musb_channel->max_packet_sz - 1)))
- ) {
+ if (musb_channel->transmit &&
+ (!channel->desired_mode ||
+ (channel->actual_len %
+ musb_channel->max_packet_sz))) {
u8 epnum = musb_channel->epnum;
int offset = musb->io.ep_offset(epnum,
MUSB_TXCSR);
@@ -363,11 +361,14 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
*/
musb_ep_select(mbase, epnum);
txcsr = musb_readw(mbase, offset);
- txcsr &= ~(MUSB_TXCSR_DMAENAB
+ if (channel->desired_mode == 1) {
+ txcsr &= ~(MUSB_TXCSR_DMAENAB
| MUSB_TXCSR_AUTOSET);
- musb_writew(mbase, offset, txcsr);
- /* Send out the packet */
- txcsr &= ~MUSB_TXCSR_DMAMODE;
+ musb_writew(mbase, offset, txcsr);
+ /* Send out the packet */
+ txcsr &= ~MUSB_TXCSR_DMAMODE;
+ txcsr |= MUSB_TXCSR_DMAENAB;
+ }
txcsr |= MUSB_TXCSR_TXPKTRDY;
musb_writew(mbase, offset, txcsr);
}