Commit 237ec709 authored Mar 18, 2016 by Mario Six Committed by Vinod Koul Apr 04, 2016

dmaengine: mpc512x: Fix hanging DMA device transfer for MPC8308



Since the MPC8308 has no external request lines to initiate DMA transfers,
all transfers must be triggered by software.

Because of this, the current implementation of DMA transfers from and to
devices on MPC8308 SoCs using major and minor loops is faulty: After the
completion of the first major loop, the DMA engine resets the start flag in
the channel's TCD, thus halting the transfer. The driver would have to set
the start bit again to trigger the next iteration of the major loop; on
MPC512x SoCs, this is done via the external request lines, so in this case,
the driver doesn't have to interfer in any way.

This has the effect that on MPC8308s, every DMA transfer to or from a
device hangs after executing the first major loop.

The patch fixes this behavior by using just one major loop for the whole
DMA transfer on MPC8308s.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

parent f55532a0

drivers/dma/mpc512x_dma.c

+24 −14

Original line number	Diff line number	Diff line
		@@ -760,6 +760,15 @@ mpc_dma_prep_slave_sg(struct dma_chan chan, struct scatterlist sgl,
		tcd->ssize = MPC_DMA_TSIZE_4;
		tcd->dsize = MPC_DMA_TSIZE_4;

		if (mdma->is_mpc8308) {
		tcd->nbytes = sg_dma_len(sg);
		if (!IS_ALIGNED(tcd->nbytes, 4))
		goto err_prep;

		/* No major loops for MPC8303 */
		tcd->biter = 1;
		tcd->citer = 1;
		} else {
		len = sg_dma_len(sg);
		tcd->nbytes = tcd_nunits * 4;
		if (!IS_ALIGNED(len, tcd->nbytes))
		@@ -775,6 +784,7 @@ mpc_dma_prep_slave_sg(struct dma_chan chan, struct scatterlist sgl,
		tcd->biter_linkch = iter >> 9;
		tcd->citer = tcd->biter;
		tcd->citer_linkch = tcd->biter_linkch;
		}

		tcd->e_sg = 0;
		tcd->d_req = 1;

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