Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4e30a373 authored by Prashant Laddha's avatar Prashant Laddha Committed by Mauro Carvalho Chehab
Browse files

[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: default avatarPrashant Laddha <prladdha@cisco.com>
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 559addc2

drivers/media/platform/vivid/vivid-sdr-cap.c

+27 −39
Original line number Diff line number Diff line
@@ -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] */