[media] vivid sdr: Use LUT based implementation for sin/cos()

The common implementation for sin/cos in include/linux/fixp-arith.h
has been improved recently to provide higher precision.

Replacing native implementation of sin/cos in vivid sdr with common
implementation. This serves two purposes:

1. Improved accuracy: the native implementation based on the Taylor
   series is more prone to rounding errors.
2. Reuse of common function: this is better compared to maintaining
   native versions for each driver.

Suggested by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

diff --git a/drivers/media/platform/vivid/vivid-sdr-cap.c b/drivers/media/platform/vivid/vivid-sdr-cap.c
index 4af55f18829f78eb640d2677d6535cfb387a291a..5e089cb58a38c29c99dadc006b4587a9498e8b1c 100644 (file)
--- a/drivers/media/platform/vivid/vivid-sdr-cap.c
+++ b/drivers/media/platform/vivid/vivid-sdr-cap.c
@@ -27,6 +27,7 @@
 #include <media/v4l2-common.h>
 #include <media/v4l2-event.h>
 #include <media/v4l2-dv-timings.h>
+#include <linux/fixp-arith.h>
 
 #include "vivid-core.h"
 #include "vivid-ctrls.h"
@@ -423,40 +424,19 @@ int vidioc_g_fmt_sdr_cap(struct file *file, void *fh, struct v4l2_format *f)
        return 0;
 }
 
-#define FIXP_FRAC    (1 << 15)
-#define FIXP_PI      ((int)(FIXP_FRAC * 3.141592653589))
-
-/* cos() from cx88 driver: cx88-dsp.c */
-static s32 fixp_cos(unsigned int x)
-{
-       u32 t2, t4, t6, t8;
-       u16 period = x / FIXP_PI;
-
-       if (period % 2)
-               return -fixp_cos(x - FIXP_PI);
-       x = x % FIXP_PI;
-       if (x > FIXP_PI/2)
-               return -fixp_cos(FIXP_PI/2 - (x % (FIXP_PI/2)));
-       /* Now x is between 0 and FIXP_PI/2.
-        * To calculate cos(x) we use it's Taylor polinom. */
-       t2 = x*x/FIXP_FRAC/2;
-       t4 = t2*x/FIXP_FRAC*x/FIXP_FRAC/3/4;
-       t6 = t4*x/FIXP_FRAC*x/FIXP_FRAC/5/6;
-       t8 = t6*x/FIXP_FRAC*x/FIXP_FRAC/7/8;
-       return FIXP_FRAC-t2+t4-t6+t8;
-}
-
-static inline s32 fixp_sin(unsigned int x)
-{
-       return -fixp_cos(x + (FIXP_PI / 2));
-}
+#define FIXP_N    (15)
+#define FIXP_FRAC (1 << FIXP_N)
+#define FIXP_2PI  ((int)(2 * 3.141592653589 * FIXP_FRAC))
 
 void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
 {
        u8 *vbuf = vb2_plane_vaddr(&buf->vb, 0);
        unsigned long i;
        unsigned long plane_size = vb2_plane_size(&buf->vb, 0);
-       int fixp_src_phase_step, fixp_i, fixp_q;
+       s32 src_phase_step;
+       s32 mod_phase_step;
+       s32 fixp_i;
+       s32 fixp_q;
 
        /*
         * TODO: Generated beep tone goes very crackly when sample rate is
@@ -466,28 +446,36 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
 
        /* calculate phase step */
        #define BEEP_FREQ 1000 /* 1kHz beep */
-       fixp_src_phase_step = DIV_ROUND_CLOSEST(2 * FIXP_PI * BEEP_FREQ,
+       src_phase_step = DIV_ROUND_CLOSEST(FIXP_2PI * BEEP_FREQ,
                        dev->sdr_adc_freq);
 
        for (i = 0; i < plane_size; i += 2) {
-               dev->sdr_fixp_mod_phase += fixp_cos(dev->sdr_fixp_src_phase);
-               dev->sdr_fixp_src_phase += fixp_src_phase_step;
+               mod_phase_step = fixp_cos32_rad(dev->sdr_fixp_src_phase,
+                                               FIXP_2PI) >> (31 - FIXP_N);
+
+               dev->sdr_fixp_src_phase += src_phase_step;
+               dev->sdr_fixp_mod_phase += mod_phase_step;
 
                /*
                 * Transfer phases to [0 / 2xPI] in order to avoid variable
                 * overflow and make it suitable for cosine implementation
                 * used, which does not support negative angles.
                 */
-               while (dev->sdr_fixp_mod_phase < (0 * FIXP_PI))
-                       dev->sdr_fixp_mod_phase += (2 * FIXP_PI);
-               while (dev->sdr_fixp_mod_phase > (2 * FIXP_PI))
-                       dev->sdr_fixp_mod_phase -= (2 * FIXP_PI);
+               while (dev->sdr_fixp_mod_phase < FIXP_2PI)
+                       dev->sdr_fixp_mod_phase += FIXP_2PI;
+               while (dev->sdr_fixp_mod_phase > FIXP_2PI)
+                       dev->sdr_fixp_mod_phase -= FIXP_2PI;
+
+               while (dev->sdr_fixp_src_phase > FIXP_2PI)
+                       dev->sdr_fixp_src_phase -= FIXP_2PI;
 
-               while (dev->sdr_fixp_src_phase > (2 * FIXP_PI))
-                       dev->sdr_fixp_src_phase -= (2 * FIXP_PI);
+               fixp_i = fixp_cos32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
+               fixp_q = fixp_sin32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
 
-               fixp_i = fixp_cos(dev->sdr_fixp_mod_phase);
-               fixp_q = fixp_sin(dev->sdr_fixp_mod_phase);
+               /* Normalize fraction values represented with 32 bit precision
+                * to fixed point representation with FIXP_N bits */
+               fixp_i >>= (31 - FIXP_N);
+               fixp_q >>= (31 - FIXP_N);
 
                /* convert 'fixp float' to u8 */
                /* u8 = X * 127.5f + 127.5f; where X is float [-1.0 / +1.0] */