[PATCH] media: xilinx: vtc: Dynamically calculate pixel clock

[Rajesh Gugulothu]

This update enables the vtc to set the pixel clock based on the
specified timing parameters. A new fps field is added to struct
xvtc_config and the pixel rate is computed as fps * hsize * vsize.
After setting the rate, the actual clock rate is read back and a
warning is emitted if it deviates beyond a small tolerance.

The pixel rate is computed in unsigned long arithmetic to avoid a 32-bit
overflow in the fps * hsize * vsize product.

Signed-off-by: Rajesh Gugulothu <rajesh.gugulothu@xxxxxxx>
---
 drivers/media/platform/xilinx/xilinx-vtc.c | 19 +++++++++++++++++++
 drivers/media/platform/xilinx/xilinx-vtc.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/drivers/media/platform/xilinx/xilinx-vtc.c b/drivers/media/platform/xilinx/xilinx-vtc.c
index 92fec7bb4..695eb2a46 100644
--- a/drivers/media/platform/xilinx/xilinx-vtc.c
+++ b/drivers/media/platform/xilinx/xilinx-vtc.c
@@ -141,6 +141,9 @@
 
 #define XVTC_GENERATOR_GLOBAL_DELAY		0x0104
 
+/* Value of 1 = .01% */
+#define XVTC_CLK_MAX_PCT_ERR			1
+
 /**
  * struct xvtc_device - Xilinx Video Timing Controller device structure
  * @xvip: Xilinx Video IP device
@@ -175,10 +178,26 @@ int xvtc_generator_start(struct xvtc_device *xvtc,
 			 const struct xvtc_config *config)
 {
 	int ret;
+	unsigned long s_rate;
+	unsigned long g_rate;
+	unsigned long clk_err;
 
 	if (!xvtc->has_generator)
 		return -ENXIO;
 
+	s_rate = (unsigned long)config->fps * config->hsize * config->vsize;
+	ret = clk_set_rate(xvtc->xvip.clk, s_rate);
+	if (ret < 0)
+		return ret;
+
+	/* Verify that the clock is within a reasonable tolerance. */
+	g_rate = clk_get_rate(xvtc->xvip.clk);
+	clk_err = (abs(g_rate - s_rate) * 10000) / (s_rate);
+	if (clk_err > XVTC_CLK_MAX_PCT_ERR)
+		dev_warn(xvtc->xvip.dev,
+			 "Failed to set clk rate: %lu, actual rate: %lu\n",
+			 s_rate, g_rate);
+
 	ret = clk_prepare_enable(xvtc->xvip.clk);
 	if (ret < 0)
 		return ret;
diff --git a/drivers/media/platform/xilinx/xilinx-vtc.h b/drivers/media/platform/xilinx/xilinx-vtc.h
index 855845911..0f360ed55 100644
--- a/drivers/media/platform/xilinx/xilinx-vtc.h
+++ b/drivers/media/platform/xilinx/xilinx-vtc.h
@@ -27,6 +27,7 @@ struct xvtc_config {
 	unsigned int vsync_start;
 	unsigned int vsync_end;
 	unsigned int vsize;
+	unsigned int fps;
 };
 
 struct xvtc_device *xvtc_of_get(struct device_node *np);
-- 
2.34.1