From 754416e10beb067e0bb473e00bf210c6f268e666 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 3 Dec 2014 15:09:50 +0100 Subject: [PATCH] dma: cppi41: add a delay while setting the TD bit The manual says that we need to (repeatedly) set the TearDown-bit for the endpoint in order to get the active transfer descriptor released. Doing this "real" quick over and over again seems to work but it also seems that the hardware might not have enough time to breathe. So I though, hey lets add a udelay() between between the individual sets of the bit. This change with the g_zero testcase resulted in a warning about missing transfer descriptor (we got the tear-down one). It seems that if the hardware has some time it manages to release the transfer-descriptor on the completion queue after the teaddown descriptor. With this change, I observe that the transfer descriptor is released after 20-30 retry loops. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Vinod Koul --- drivers/dma/cppi41.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/dma/cppi41.c b/drivers/dma/cppi41.c index 3fb7931..b743adf 100644 --- a/drivers/dma/cppi41.c +++ b/drivers/dma/cppi41.c @@ -1,3 +1,4 @@ +#include #include #include #include @@ -603,12 +604,16 @@ static int cppi41_tear_down_chan(struct cppi41_channel *c) * descriptor before the TD we fetch it from enqueue, it has to be * there waiting for us. */ - if (!c->td_seen && c->td_retry) + if (!c->td_seen && c->td_retry) { + udelay(1); return -EAGAIN; - + } WARN_ON(!c->td_retry); + if (!c->td_desc_seen) { desc_phys = cppi41_pop_desc(cdd, c->q_num); + if (!desc_phys) + desc_phys = cppi41_pop_desc(cdd, c->q_comp_num); WARN_ON(!desc_phys); } -- 2.7.4