dmaengine: tegra-apb: Support non-flow controlled slave configuration

This allows DMA client to issue a non-flow controlled TX. In particular
it is needed for the fuse driver that reads fuse registers using APBDMA
to workaround a HW bug that results in hang when CPU and DMA perform
simultaneous access to fuse peripheral.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index b9d75a5..9a558e3 100644 (file)
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -353,7 +353,8 @@ static int tegra_dma_slave_config(struct dma_chan *dc,
        }
 
        memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
-       if (tdc->slave_id == TEGRA_APBDMA_SLAVE_ID_INVALID) {
+       if (tdc->slave_id == TEGRA_APBDMA_SLAVE_ID_INVALID &&
+           sconfig->device_fc) {
                if (sconfig->slave_id > TEGRA_APBDMA_CSR_REQ_SEL_MASK)
                        return -EINVAL;
                tdc->slave_id = sconfig->slave_id;
@@ -970,8 +971,13 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
                                        TEGRA_APBDMA_AHBSEQ_WRAP_SHIFT;
        ahb_seq |= TEGRA_APBDMA_AHBSEQ_BUS_WIDTH_32;
 
-       csr |= TEGRA_APBDMA_CSR_ONCE | TEGRA_APBDMA_CSR_FLOW;
-       csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
+       csr |= TEGRA_APBDMA_CSR_ONCE;
+
+       if (tdc->slave_id != TEGRA_APBDMA_SLAVE_ID_INVALID) {
+               csr |= TEGRA_APBDMA_CSR_FLOW;
+               csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
+       }
+
        if (flags & DMA_PREP_INTERRUPT)
                csr |= TEGRA_APBDMA_CSR_IE_EOC;
 
@@ -1110,10 +1116,13 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_dma_cyclic(
                                        TEGRA_APBDMA_AHBSEQ_WRAP_SHIFT;
        ahb_seq |= TEGRA_APBDMA_AHBSEQ_BUS_WIDTH_32;
 
-       csr |= TEGRA_APBDMA_CSR_FLOW;
+       if (tdc->slave_id != TEGRA_APBDMA_SLAVE_ID_INVALID) {
+               csr |= TEGRA_APBDMA_CSR_FLOW;
+               csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
+       }
+
        if (flags & DMA_PREP_INTERRUPT)
                csr |= TEGRA_APBDMA_CSR_IE_EOC;
-       csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 
        apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;