From 13bbfb5c4eb4fc85bf977245f9b3624df0187184 Mon Sep 17 00:00:00 2001 From: Daniel Mack Date: Mon, 26 May 2014 14:52:34 +0200 Subject: [PATCH] dma: cppi41: handle 0-length packets When a 0-length packet is received on the bus, desc->pd0 yields 1, which confuses the driver's users. This information is clearly wrong and not in accordance to the datasheet, but it's been observed 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 the value in PD0 and report a total length of 0 instead. Signed-off-by: Daniel Mack Signed-off-by: Vinod Koul --- 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 d028f36ae655..8f8b0b608875 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); } -- 2.20.1