[PATCH v2] dmaengine: tegra-apb: proper default init of channel slave_id

[Shardar Shariff Md <smohammed@nvidia.com>]

Initialize default channel slave_id(req_sel) to invalid id
(i.e max supported slave id + 1) to avoid overwriting of slave_id
during tegra_dma_slave_config() with client data if slave_id
is not initialized through DT

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>

---
- Instead of initializing the slave id to -1 define macros for
  max slave id and invalid slave id and do the checks accordingly.
---
 drivers/dma/tegra20-apb-dma.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 3871f29..2957e26 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -114,6 +114,9 @@
 /* Channel base address offset from APBDMA base address */
 #define TEGRA_APBDMA_CHANNEL_BASE_ADD_OFFSET	0x1000
 
+#define TEGRA_APBDMA_SLAVE_ID_MAX		31
+#define TEGRA_APBDMA_SLAVE_ID_INVALID		(TEGRA_APBDMA_SLAVE_ID_MAX + 1)
+
 struct tegra_dma;
 
 /*
@@ -353,7 +356,7 @@ static int tegra_dma_slave_config(struct dma_chan *dc,
 	}
 
 	memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
-	if (!tdc->slave_id)
+	if (tdc->slave_id == TEGRA_APBDMA_SLAVE_ID_INVALID)
 		tdc->slave_id = sconfig->slave_id;
 	tdc->config_init = true;
 	return 0;
@@ -1236,7 +1239,7 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 	}
 	pm_runtime_put(tdma->dev);
 
-	tdc->slave_id = 0;
+	tdc->slave_id = TEGRA_APBDMA_SLAVE_ID_INVALID;
 }
 
 static struct dma_chan *tegra_dma_of_xlate(struct of_phandle_args *dma_spec,
@@ -1253,6 +1256,11 @@ static struct dma_chan *tegra_dma_of_xlate(struct of_phandle_args *dma_spec,
 	tdc = to_tegra_dma_chan(chan);
 	tdc->slave_id = dma_spec->args[0];
 
+	if (tdc->slave_id > TEGRA_APBDMA_SLAVE_ID_MAX) {
+		dev_err(tdc2dev(tdc), "Invalid slave id\n");
+		return NULL;
+	}
+
 	return chan;
 }
 
@@ -1389,6 +1397,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
 				&tdma->dma_dev.channels);
 		tdc->tdma = tdma;
 		tdc->id = i;
+		tdc->slave_id = TEGRA_APBDMA_SLAVE_ID_INVALID;
 
 		tasklet_init(&tdc->tasklet, tegra_dma_tasklet,
 				(unsigned long)tdc);
-- 
1.8.1.5