[PATCH v4] dw_dmac: don't exceed AHB master number in dwc_get_data_width

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

The driver assumes that hardware has two AHB masters which might not be always
true. In such cases we must not exceed number of the AHB masters present in the
hardware. In the proposed scheme in this patch, we would choose the master with
highest possible number whenever we exceed max AHB masters.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
Since v3:
 - substitute "else if" by "else", we don't pass anything else than SRC_MASTER
   or DST_MASTER

 drivers/dma/dw_dmac.c |   33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 30ff2a4..2ab3f3c 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -46,13 +46,29 @@ static inline unsigned int dwc_get_sms(struct dw_dma_slave *slave)
 	return slave ? slave->src_master : 1;
 }
 
+#define SRC_MASTER	0
+#define DST_MASTER	1
+
+static inline unsigned int dwc_get_master(struct dma_chan *chan, int master)
+{
+	struct dw_dma *dw = to_dw_dma(chan->device);
+	struct dw_dma_slave *dws = chan->private;
+	unsigned int m;
+
+	if (master == SRC_MASTER)
+		m = dwc_get_sms(dws);
+	else
+		m = dwc_get_dms(dws);
+
+	return min_t(unsigned int, dw->nr_masters - 1, m);
+}
+
 #define DWC_DEFAULT_CTLLO(_chan) ({				\
-		struct dw_dma_slave *__slave = (_chan->private);	\
 		struct dw_dma_chan *_dwc = to_dw_dma_chan(_chan);	\
 		struct dma_slave_config	*_sconfig = &_dwc->dma_sconfig;	\
 		bool _is_slave = is_slave_direction(_dwc->direction);	\
-		int _dms = dwc_get_dms(__slave);		\
-		int _sms = dwc_get_sms(__slave);		\
+		int _dms = dwc_get_master(_chan, DST_MASTER);		\
+		int _sms = dwc_get_master(_chan, SRC_MASTER);		\
 		u8 _smsize = _is_slave ? _sconfig->src_maxburst :	\
 			DW_DMA_MSIZE_16;			\
 		u8 _dmsize = _is_slave ? _sconfig->dst_maxburst :	\
@@ -73,20 +89,11 @@ static inline unsigned int dwc_get_sms(struct dw_dma_slave *slave)
  */
 #define NR_DESCS_PER_CHANNEL	64
 
-#define SRC_MASTER	0
-#define DST_MASTER	1
-
 static inline unsigned int dwc_get_data_width(struct dma_chan *chan, int master)
 {
 	struct dw_dma *dw = to_dw_dma(chan->device);
-	struct dw_dma_slave *dws = chan->private;
-
-	if (master == SRC_MASTER)
-		return dw->data_width[dwc_get_sms(dws)];
-	else if (master == DST_MASTER)
-		return dw->data_width[dwc_get_dms(dws)];
 
-	return 0;
+	return dw->data_width[dwc_get_master(chan, master)];
 }
 
 /*----------------------------------------------------------------------*/
-- 
1.7.10.4