The CPPI 4.1 driver polls register to workaround the premature TX
interrupt issue, but it causes audio playback underrun when triggered in
Isoch transfers.
Isoch doesn't do back-to-back transfers, the TX should be done by the
time the next transfer is scheduled. So skip this polling workaround for
Isoch transfer.
Fixes: a655f481d83d6 ("usb: musb: musb_cppi41: handle pre-mature TX complete interrupt")
Cc: <stable@xxxxxxxxxxxxxxx> #4.1+
Reported-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Tested-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
Signed-off-by: Bin Liu <b-liu@xxxxxx>
---
v2: fix typo in commit comments.
drivers/usb/musb/musb_cppi41.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 00e272bfee39..355655f8a3fb 100644
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -238,8 +238,27 @@ static void cppi41_dma_callback(void *private_data,
transferred < cppi41_channel->packet_sz)
cppi41_channel->prog_len = 0;
- if (cppi41_channel->is_tx)
- empty = musb_is_tx_fifo_empty(hw_ep);
+ if (cppi41_channel->is_tx) {
+ u8 type;
+
+ if (is_host_active(musb))
+ type = hw_ep->out_qh->type;
+ else
+ type = hw_ep->ep_in.type;
+
+ if (type == USB_ENDPOINT_XFER_ISOC)
+ /*
+ * Don't use the early-TX-interrupt workaround below
+ * for Isoch transfter. Since Isoch are periodic
+ * transfer, by the time the next transfer is
+ * scheduled, the current one should be done already.
+ *
+ * This avoids audio playback underrun issue.
+ */
+ empty = true;
+ else
+ empty = musb_is_tx_fifo_empty(hw_ep);
+ }
if (!cppi41_channel->is_tx || empty) {
cppi41_trans_done(cppi41_channel);
--
1.9.1
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