dmaengine: shdma: Make second memory window optional

This patch makes the shdma.c driver allow slave operation
on DMA hardware mapped with a single I/O-memory window.

The dmae_set_dmars() function is adjusted to use the
first memory window in case of a missing DMARS window.

At probe() time the code is updated to enable DMA_SLAVE
only if slave information is passed with the platform data.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/dma/shdma.c b/drivers/dma/shdma.c
index dcc1b2139fff..3391b157d057 100644
--- a/drivers/dma/shdma.c
+++ b/drivers/dma/shdma.c
@@ -213,12 +213,17 @@ static int dmae_set_dmars(struct sh_dmae_chan *sh_chan, u16 val)
                                                 struct sh_dmae_device, common);
         struct sh_dmae_pdata *pdata = shdev->pdata;
         const struct sh_dmae_channel *chan_pdata = &pdata->channel[sh_chan->id];
-        u16 __iomem *addr = shdev->dmars + chan_pdata->dmars / sizeof(u16);
+        u16 __iomem *addr = shdev->dmars;
         int shift = chan_pdata->dmars_bit;
 
         if (dmae_is_busy(sh_chan))
                 return -EBUSY;
 
+        /* in the case of a missing DMARS resource use first memory window */
+        if (!addr)
+                addr = (u16 __iomem *)shdev->chan_reg;
+        addr += chan_pdata->dmars / sizeof(u16);
+
         __raw_writew((__raw_readw(addr) & (0xff00 >> shift)) | (val << shift),
                      addr);
 
@@ -1087,7 +1092,7 @@ static int __init sh_dmae_probe(struct platform_device *pdev)
                 return -ENODEV;
 
         chan = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-        /* DMARS area is optional, if absent, this controller cannot do slave DMA */
+        /* DMARS area is optional */
         dmars = platform_get_resource(pdev, IORESOURCE_MEM, 1);
         /*
          * IRQ resources:
@@ -1154,7 +1159,7 @@ static int __init sh_dmae_probe(struct platform_device *pdev)
         INIT_LIST_HEAD(&shdev->common.channels);
 
         dma_cap_set(DMA_MEMCPY, shdev->common.cap_mask);
-        if (dmars)
+        if (pdata->slave && pdata->slave_num)
                 dma_cap_set(DMA_SLAVE, shdev->common.cap_mask);
 
         shdev->common.device_alloc_chan_resources