[PATCH v2 3/5] dmaengine: qcom: bam_dma: add controlled remotely dt property

[Stanimir Varbanov]

Some of the peripherals has bam which is controlled by remote
processor, thus the bam dma driver must avoid register writes
which initialise bam hw block. Those registers are protected
from xPU block and any writes to them will lead to secure
violation and system reboot.

Adding the contolled_remotely flag in bam driver to avoid
not permitted register writes in bam_init function.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov at linaro.org>
Reviewed-by: Andy Gross <andy.gross at linaro.org>
---
 Documentation/devicetree/bindings/dma/qcom_bam_dma.txt | 2 ++
 drivers/dma/qcom/bam_dma.c                             | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt b/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
index 1c9d48ea4914..9cbf5d9df8fd 100644
--- a/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
+++ b/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
@@ -13,6 +13,8 @@ Required properties:
 - clock-names: must contain "bam_clk" entry
 - qcom,ee : indicates the active Execution Environment identifier (0-7) used in
   the secure world.
+- qcom,controlled-remotely : optional, indicates that the bam is controlled by
+  remote proccessor i.e. execution environment.
 
 Example:
 
diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index 789d5f836bf7..d0f878a78fae 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -387,6 +387,7 @@ struct bam_device {
 
 	/* execution environment ID, from DT */
 	u32 ee;
+	bool controlled_remotely;
 
 	const struct reg_offset_data *layout;
 
@@ -1042,6 +1043,9 @@ static int bam_init(struct bam_device *bdev)
 	val = readl_relaxed(bam_addr(bdev, 0, BAM_NUM_PIPES));
 	bdev->num_channels = val & BAM_NUM_PIPES_MASK;
 
+	if (bdev->controlled_remotely)
+		return 0;
+
 	/* s/w reset bam */
 	/* after reset all pipes are disabled and idle */
 	val = readl_relaxed(bam_addr(bdev, 0, BAM_CTRL));
@@ -1129,6 +1133,9 @@ static int bam_dma_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	bdev->controlled_remotely = of_property_read_bool(pdev->dev.of_node,
+						"qcom,controlled-remotely");
+
 	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
 	if (IS_ERR(bdev->bamclk))
 		return PTR_ERR(bdev->bamclk);
-- 
1.9.1