[media] coda: Use S_PARM to set nominal framerate for h.264 encoder

The encoder needs to know the nominal framerate for the constant bitrate
control mechanism to work. Currently the only way to set the framerate is
by using VIDIOC_S_PARM on the output queue.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

2 files changed, 106 insertions, 0 deletions

diff --git a/drivers/media/platform/coda/coda-common.c b/drivers/media/platform/coda/coda-common.c
index 24737f1..a7cab14 100644
--- a/drivers/media/platform/coda/coda-common.c
+++ b/drivers/media/platform/coda/coda-common.c
@@ -15,6 +15,7 @@
 #include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/firmware.h>
+#include <linux/gcd.h>
 #include <linux/genalloc.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -770,6 +771,104 @@ static int coda_decoder_cmd(struct file *file, void *fh,
 	return 0;
 }
 
+static int coda_g_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
+{
+	struct coda_ctx *ctx = fh_to_ctx(fh);
+	struct v4l2_fract *tpf;
+
+	if (a->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
+		return -EINVAL;
+
+	a->parm.output.capability = V4L2_CAP_TIMEPERFRAME;
+	tpf = &a->parm.output.timeperframe;
+	tpf->denominator = ctx->params.framerate & CODA_FRATE_RES_MASK;
+	tpf->numerator = 1 + (ctx->params.framerate >>
+			      CODA_FRATE_DIV_OFFSET);
+
+	return 0;
+}
+
+/*
+ * Approximate timeperframe v4l2_fract with values that can be written
+ * into the 16-bit CODA_FRATE_DIV and CODA_FRATE_RES fields.
+ */
+static void coda_approximate_timeperframe(struct v4l2_fract *timeperframe)
+{
+	struct v4l2_fract s = *timeperframe;
+	struct v4l2_fract f0;
+	struct v4l2_fract f1 = { 1, 0 };
+	struct v4l2_fract f2 = { 0, 1 };
+	unsigned int i, div, s_denominator;
+
+	/* Lower bound is 1/65535 */
+	if (s.numerator == 0 || s.denominator / s.numerator > 65535) {
+		timeperframe->numerator = 1;
+		timeperframe->denominator = 65535;
+		return;
+	}
+
+	/* Upper bound is 65536/1, map everything above to infinity */
+	if (s.denominator == 0 || s.numerator / s.denominator > 65536) {
+		timeperframe->numerator = 1;
+		timeperframe->denominator = 0;
+		return;
+	}
+
+	/* Reduce fraction to lowest terms */
+	div = gcd(s.numerator, s.denominator);
+	if (div > 1) {
+		s.numerator /= div;
+		s.denominator /= div;
+	}
+
+	if (s.numerator <= 65536 && s.denominator < 65536) {
+		*timeperframe = s;
+		return;
+	}
+
+	/* Find successive convergents from continued fraction expansion */
+	while (f2.numerator <= 65536 && f2.denominator < 65536) {
+		f0 = f1;
+		f1 = f2;
+
+		/* Stop when f2 exactly equals timeperframe */
+		if (s.numerator == 0)
+			break;
+
+		i = s.denominator / s.numerator;
+
+		f2.numerator = f0.numerator + i * f1.numerator;
+		f2.denominator = f0.denominator + i * f2.denominator;
+
+		s_denominator = s.numerator;
+		s.numerator = s.denominator % s.numerator;
+		s.denominator = s_denominator;
+	}
+
+	*timeperframe = f1;
+}
+
+static uint32_t coda_timeperframe_to_frate(struct v4l2_fract *timeperframe)
+{
+	return ((timeperframe->numerator - 1) << CODA_FRATE_DIV_OFFSET) |
+		timeperframe->denominator;
+}
+
+static int coda_s_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
+{
+	struct coda_ctx *ctx = fh_to_ctx(fh);
+	struct v4l2_fract *tpf;
+
+	if (a->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
+		return -EINVAL;
+
+	tpf = &a->parm.output.timeperframe;
+	coda_approximate_timeperframe(tpf);
+	ctx->params.framerate = coda_timeperframe_to_frate(tpf);
+
+	return 0;
+}
+
 static int coda_subscribe_event(struct v4l2_fh *fh,
 				const struct v4l2_event_subscription *sub)
 {
@@ -810,6 +909,9 @@ static const struct v4l2_ioctl_ops coda_ioctl_ops = {
 	.vidioc_try_decoder_cmd	= coda_try_decoder_cmd,
 	.vidioc_decoder_cmd	= coda_decoder_cmd,
 
+	.vidioc_g_parm		= coda_g_parm,
+	.vidioc_s_parm		= coda_s_parm,
+
 	.vidioc_subscribe_event = coda_subscribe_event,
 	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
 };
diff --git a/drivers/media/platform/coda/coda_regs.h b/drivers/media/platform/coda/coda_regs.h
index 7d02624..00e4f51 100644
--- a/drivers/media/platform/coda/coda_regs.h
+++ b/drivers/media/platform/coda/coda_regs.h
@@ -263,6 +263,10 @@
 #define		CODADX6_PICHEIGHT_MASK				0x3ff
 #define		CODA7_PICHEIGHT_MASK				0xffff
 #define CODA_CMD_ENC_SEQ_SRC_F_RATE				0x194
+#define		CODA_FRATE_RES_OFFSET				0
+#define		CODA_FRATE_RES_MASK				0xffff
+#define		CODA_FRATE_DIV_OFFSET				16
+#define		CODA_FRATE_DIV_MASK				0xffff
 #define CODA_CMD_ENC_SEQ_MP4_PARA				0x198
 #define		CODA_MP4PARAM_VERID_OFFSET			6
 #define		CODA_MP4PARAM_VERID_MASK			0x01