[media] vivid: sdr cap: few enhancements

* Constify struct

* Fix comments

* Fix alignment

* Use modulus to transfer phase angles

* Correct float [-1.0, +1.0] to s8 [-128, 127] conversion

Signed-off-by: Antti Palosaari <crope@iki.fi>
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 c36b3f58dab69c7354b83e23869bdc2e5780f827..d0c26577c06ea29139942211ea5863982fe1ff43 100644 (file)
--- a/drivers/media/platform/vivid/vivid-sdr-cap.c
+++ b/drivers/media/platform/vivid/vivid-sdr-cap.c
@@ -41,7 +41,7 @@ struct vivid_format {
 };
 
 /* format descriptions for capture and preview */
-static struct vivid_format formats[] = {
+static const struct vivid_format formats[] = {
        {
                .pixelformat    = V4L2_SDR_FMT_CU8,
                .buffersize     = SDR_CAP_SAMPLES_PER_BUF * 2,
@@ -502,16 +502,10 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
        s32 fixp_i;
        s32 fixp_q;
 
-       /*
-        * TODO: Generated beep tone goes very crackly when sample rate is
-        * increased to ~1Msps or more. That is because of huge rounding error
-        * of phase angle caused by used cosine implementation.
-        */
-
        /* calculate phase step */
        #define BEEP_FREQ 1000 /* 1kHz beep */
        src_phase_step = DIV_ROUND_CLOSEST(FIXP_2PI * BEEP_FREQ,
-                       dev->sdr_adc_freq);
+                                          dev->sdr_adc_freq);
 
        for (i = 0; i < plane_size; i += 2) {
                mod_phase_step = fixp_cos32_rad(dev->sdr_fixp_src_phase,
@@ -522,17 +516,15 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
                dev->sdr_fixp_mod_phase += div_s64(s64tmp, M_100000PI);
 
                /*
-                * Transfer phases to [0 / 2xPI] in order to avoid variable
+                * Transfer phase angle 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 < FIXP_2PI)
-                       dev->sdr_fixp_mod_phase += FIXP_2PI;
-               while (dev->sdr_fixp_mod_phase > FIXP_2PI)
-                       dev->sdr_fixp_mod_phase -= FIXP_2PI;
+               dev->sdr_fixp_src_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;
+               if (dev->sdr_fixp_mod_phase < 0)
+                       dev->sdr_fixp_mod_phase += FIXP_2PI;
 
                fixp_i = fixp_cos32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
                fixp_q = fixp_sin32_rad(dev->sdr_fixp_mod_phase, FIXP_2PI);
@@ -544,7 +536,7 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
 
                switch (dev->sdr_pixelformat) {
                case V4L2_SDR_FMT_CU8:
-                       /* convert 'fixp float' to u8 */
+                       /* convert 'fixp float' to u8 [0, +255] */
                        /* u8 = X * 127.5 + 127.5; X is float [-1.0, +1.0] */
                        fixp_i = fixp_i * 1275 + FIXP_FRAC * 1275;
                        fixp_q = fixp_q * 1275 + FIXP_FRAC * 1275;
@@ -552,9 +544,10 @@ void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
                        *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
                        break;
                case V4L2_SDR_FMT_CS8:
-                       /* convert 'fixp float' to s8 */
-                       fixp_i = fixp_i * 1275;
-                       fixp_q = fixp_q * 1275;
+                       /* convert 'fixp float' to s8 [-128, +127] */
+                       /* s8 = X * 127.5 - 0.5; X is float [-1.0, +1.0] */
+                       fixp_i = fixp_i * 1275 - FIXP_FRAC * 5;
+                       fixp_q = fixp_q * 1275 - FIXP_FRAC * 5;
                        *vbuf++ = DIV_ROUND_CLOSEST(fixp_i, FIXP_FRAC * 10);
                        *vbuf++ = DIV_ROUND_CLOSEST(fixp_q, FIXP_FRAC * 10);
                        break;