[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 24737f1a1a1b..a7cab14d10c9 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 7d026241171b..00e4f5160c1f 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