When a 0-length packet is received on the bus, desc->pd6 contains 1, and
the current residue calculation reports back that 1 byte has been
transferred. This is not according to what the datasheet says, but it's
been the case on an AM335x board, very reproducible.
Fix this by looking at bit 19 in PD2 of the completed packet. This bit
will tell us if a zero-length packet was received on a queue. If it's
set, ignore pd2 and report a total length of 0.
Signed-off-by: Daniel Mack <zonque@xxxxxxxxx>
---
drivers/dma/cppi41.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/dma/cppi41.c b/drivers/dma/cppi41.c
index d028f36..8f8b0b6 100644
--- a/drivers/dma/cppi41.c
+++ b/drivers/dma/cppi41.c
@@ -86,6 +86,9 @@
#define USBSS_IRQ_PD_COMP (1 << 2)
+/* Packet Descriptor */
+#define PD2_ZERO_LENGTH (1 << 19)
+
struct cppi41_channel {
struct dma_chan chan;
struct dma_async_tx_descriptor txd;
@@ -307,7 +310,7 @@ static irqreturn_t cppi41_irq(int irq, void *data)
__iormb();
while (val) {
- u32 desc;
+ u32 desc, len;
q_num = __fls(val);
val &= ~(1 << q_num);
@@ -319,9 +322,13 @@ static irqreturn_t cppi41_irq(int irq, void *data)
q_num, desc);
continue;
}
- c->residue = pd_trans_len(c->desc->pd6) -
- pd_trans_len(c->desc->pd0);
+ if (c->desc->pd2 & PD2_ZERO_LENGTH)
+ len = 0;
+ else
+ len = pd_trans_len(c->desc->pd0);
+
+ c->residue = pd_trans_len(c->desc->pd6) - len;
dma_cookie_complete(&c->txd);
c->txd.callback(c->txd.callback_param);
}
--
1.9.0
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