[media] media: imx: csi: add frame skipping support

The CSI can skip any out of up to 6 input frames, allowing to reduce the
frame rate at the output pads by small fractions.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
index ec4f9f88712c9fa853f38b5462062fd16cc8d932..e6188900f5eaa2ebe0af8891eb9b70525d9e04bc 100644 (file)
--- a/drivers/staging/media/imx/imx-media-csi.c
+++ b/drivers/staging/media/imx/imx-media-csi.c
@@ -2,6 +2,7 @@
  * V4L2 Capture CSI Subdev for Freescale i.MX5/6 SOC
  *
  * Copyright (c) 2014-2017 Mentor Graphics Inc.
+ * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@pengutronix.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -9,6 +10,7 @@
  * (at your option) any later version.
  */
 #include <linux/delay.h>
+#include <linux/gcd.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/pinctrl/consumer.h>
@@ -42,6 +44,18 @@
 #define H_ALIGN    1 /* multiple of 2 lines */
 #define S_ALIGN    1 /* multiple of 2 */
 
+/*
+ * struct csi_skip_desc - CSI frame skipping descriptor
+ * @keep - number of frames kept per max_ratio frames
+ * @max_ratio - width of skip_smfc, written to MAX_RATIO bitfield
+ * @skip_smfc - skip pattern written to the SKIP_SMFC bitfield
+ */
+struct csi_skip_desc {
+       u8 keep;
+       u8 max_ratio;
+       u8 skip_smfc;
+};
+
 struct csi_priv {
        struct device *dev;
        struct ipu_soc *ipu;
@@ -65,8 +79,9 @@ struct csi_priv {
 
        struct v4l2_mbus_framefmt format_mbus[CSI_NUM_PADS];
        const struct imx_media_pixfmt *cc[CSI_NUM_PADS];
-       struct v4l2_fract frame_interval;
+       struct v4l2_fract frame_interval[CSI_NUM_PADS];
        struct v4l2_rect crop;
+       const struct csi_skip_desc *skip;
 
        /* active vb2 buffers to send to video dev sink */
        struct imx_media_buffer *active_vb2_buf[2];
@@ -581,6 +596,10 @@ static int csi_setup(struct csi_priv *priv)
 
        ipu_csi_set_dest(priv->csi, priv->dest);
 
+       if (priv->dest == IPU_CSI_DEST_IDMAC)
+               ipu_csi_set_skip_smfc(priv->csi, priv->skip->skip_smfc,
+                                     priv->skip->max_ratio - 1, 0);
+
        ipu_csi_dump(priv->csi);
 
        return 0;
@@ -588,6 +607,7 @@ static int csi_setup(struct csi_priv *priv)
 
 static int csi_start(struct csi_priv *priv)
 {
+       struct v4l2_fract *output_fi, *input_fi;
        u32 bad_frames = 0;
        int ret;
 
@@ -596,10 +616,12 @@ static int csi_start(struct csi_priv *priv)
                return -EINVAL;
        }
 
+       output_fi = &priv->frame_interval[priv->active_output_pad];
+       input_fi = &priv->frame_interval[CSI_SINK_PAD];
+
        ret = v4l2_subdev_call(priv->sensor->sd, sensor,
                               g_skip_frames, &bad_frames);
        if (!ret && bad_frames) {
-               struct v4l2_fract *fi = &priv->frame_interval;
                u32 delay_usec;
 
                /*
@@ -610,8 +632,8 @@ static int csi_start(struct csi_priv *priv)
                 * to lose vert/horiz sync.
                 */
                delay_usec = DIV_ROUND_UP_ULL(
-                       (u64)USEC_PER_SEC * fi->numerator * bad_frames,
-                       fi->denominator);
+                       (u64)USEC_PER_SEC * input_fi->numerator * bad_frames,
+                       input_fi->denominator);
                usleep_range(delay_usec, delay_usec + 1000);
        }
 
@@ -627,8 +649,7 @@ static int csi_start(struct csi_priv *priv)
 
        /* start the frame interval monitor */
        if (priv->fim && priv->dest == IPU_CSI_DEST_IDMAC) {
-               ret = imx_media_fim_set_stream(priv->fim, &priv->frame_interval,
-                                              true);
+               ret = imx_media_fim_set_stream(priv->fim, output_fi, true);
                if (ret)
                        goto idmac_stop;
        }
@@ -643,8 +664,7 @@ static int csi_start(struct csi_priv *priv)
 
 fim_off:
        if (priv->fim && priv->dest == IPU_CSI_DEST_IDMAC)
-               imx_media_fim_set_stream(priv->fim, &priv->frame_interval,
-                                        false);
+               imx_media_fim_set_stream(priv->fim, NULL, false);
 idmac_stop:
        if (priv->dest == IPU_CSI_DEST_IDMAC)
                csi_idmac_stop(priv);
@@ -658,14 +678,85 @@ static void csi_stop(struct csi_priv *priv)
 
                /* stop the frame interval monitor */
                if (priv->fim)
-                       imx_media_fim_set_stream(priv->fim,
-                                                &priv->frame_interval,
-                                                false);
+                       imx_media_fim_set_stream(priv->fim, NULL, false);
        }
 
        ipu_csi_disable(priv->csi);
 }
 
+static const struct csi_skip_desc csi_skip[12] = {
+       { 1, 1, 0x00 }, /* Keep all frames */
+       { 5, 6, 0x10 }, /* Skip every sixth frame */
+       { 4, 5, 0x08 }, /* Skip every fifth frame */
+       { 3, 4, 0x04 }, /* Skip every fourth frame */
+       { 2, 3, 0x02 }, /* Skip every third frame */
+       { 3, 5, 0x0a }, /* Skip frames 1 and 3 of every 5 */
+       { 1, 2, 0x01 }, /* Skip every second frame */
+       { 2, 5, 0x0b }, /* Keep frames 1 and 4 of every 5 */
+       { 1, 3, 0x03 }, /* Keep one in three frames */
+       { 1, 4, 0x07 }, /* Keep one in four frames */
+       { 1, 5, 0x0f }, /* Keep one in five frames */
+       { 1, 6, 0x1f }, /* Keep one in six frames */
+};
+
+static void csi_apply_skip_interval(const struct csi_skip_desc *skip,
+                                   struct v4l2_fract *interval)
+{
+       unsigned int div;
+
+       interval->numerator *= skip->max_ratio;
+       interval->denominator *= skip->keep;
+
+       /* Reduce fraction to lowest terms */
+       div = gcd(interval->numerator, interval->denominator);
+       if (div > 1) {
+               interval->numerator /= div;
+               interval->denominator /= div;
+       }
+}
+
+/*
+ * Find the skip pattern to produce the output frame interval closest to the
+ * requested one, for the given input frame interval. Updates the output frame
+ * interval to the exact value.
+ */
+static const struct csi_skip_desc *csi_find_best_skip(struct v4l2_fract *in,
+                                                     struct v4l2_fract *out)
+{
+       const struct csi_skip_desc *skip = &csi_skip[0], *best_skip = skip;
+       u32 min_err = UINT_MAX;
+       u64 want_us;
+       int i;
+
+       /* Default to 1:1 ratio */
+       if (out->numerator == 0 || out->denominator == 0 ||
+           in->numerator == 0 || in->denominator == 0) {
+               *out = *in;
+               return best_skip;
+       }
+
+       want_us = div_u64((u64)USEC_PER_SEC * out->numerator, out->denominator);
+
+       /* Find the reduction closest to the requested time per frame */
+       for (i = 0; i < ARRAY_SIZE(csi_skip); i++, skip++) {
+               u64 tmp, err;
+
+               tmp = div_u64((u64)USEC_PER_SEC * in->numerator *
+                             skip->max_ratio, in->denominator * skip->keep);
+
+               err = abs((s64)tmp - want_us);
+               if (err < min_err) {
+                       min_err = err;
+                       best_skip = skip;
+               }
+       }
+
+       *out = *in;
+       csi_apply_skip_interval(best_skip, out);
+
+       return best_skip;
+}
+
 /*
  * V4L2 subdev operations.
  */
@@ -675,8 +766,13 @@ static int csi_g_frame_interval(struct v4l2_subdev *sd,
 {
        struct csi_priv *priv = v4l2_get_subdevdata(sd);
 
+       if (fi->pad >= CSI_NUM_PADS)
+               return -EINVAL;
+
        mutex_lock(&priv->lock);
-       fi->interval = priv->frame_interval;
+
+       fi->interval = priv->frame_interval[fi->pad];
+
        mutex_unlock(&priv->lock);
 
        return 0;
@@ -686,18 +782,44 @@ static int csi_s_frame_interval(struct v4l2_subdev *sd,
                                struct v4l2_subdev_frame_interval *fi)
 {
        struct csi_priv *priv = v4l2_get_subdevdata(sd);
+       struct v4l2_fract *input_fi;
+       int ret = 0;
 
        mutex_lock(&priv->lock);
 
-       /* Output pads mirror active input pad, no limits on input pads */
-       if (fi->pad == CSI_SRC_PAD_IDMAC || fi->pad == CSI_SRC_PAD_DIRECT)
-               fi->interval = priv->frame_interval;
+       input_fi = &priv->frame_interval[CSI_SINK_PAD];
 
-       priv->frame_interval = fi->interval;
+       switch (fi->pad) {
+       case CSI_SINK_PAD:
+               /* No limits on input frame interval */
+               /* Reset output intervals and frame skipping ratio to 1:1 */
+               priv->frame_interval[CSI_SRC_PAD_IDMAC] = fi->interval;
+               priv->frame_interval[CSI_SRC_PAD_DIRECT] = fi->interval;
+               priv->skip = &csi_skip[0];
+               break;
+       case CSI_SRC_PAD_IDMAC:
+               /*
+                * frame interval at IDMAC output pad depends on input
+                * interval, modified by frame skipping.
+                */
+               priv->skip = csi_find_best_skip(input_fi, &fi->interval);
+               break;
+       case CSI_SRC_PAD_DIRECT:
+               /*
+                * frame interval at DIRECT output pad is same as input
+                * interval.
+                */
+               fi->interval = *input_fi;
+               break;
+       default:
+               ret = -EINVAL;
+               goto out;
+       }
 
+       priv->frame_interval[fi->pad] = fi->interval;
+out:
        mutex_unlock(&priv->lock);
-
-       return 0;
+       return ret;
 }
 
 static int csi_s_stream(struct v4l2_subdev *sd, int enable)
@@ -1334,11 +1456,14 @@ static int csi_registered(struct v4l2_subdev *sd)
                                              &priv->cc[i]);
                if (ret)
                        goto put_csi;
+
+               /* init default frame interval */
+               priv->frame_interval[i].numerator = 1;
+               priv->frame_interval[i].denominator = 30;
        }
 
-       /* init default frame interval */
-       priv->frame_interval.numerator = 1;
-       priv->frame_interval.denominator = 30;
+       /* disable frame skipping */
+       priv->skip = &csi_skip[0];
 
        priv->fim = imx_media_fim_init(&priv->sd);
        if (IS_ERR(priv->fim)) {