// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Stereo and SAP detection for cx88
 *
 *  Copyright (c) 2009 Marton Balint <cus@fazekas.hu>
 */

#include "cx88.h"
#include "cx88-reg.h"

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/jiffies.h>
#include <asm/div64.h>

#define INT_PI                  ((s32)(3.141592653589 * 32768.0))

#define compat_remainder(a, b) \
         ((float)(((s32)((a) * 100)) % ((s32)((b) * 100))) / 100.0)

#define baseband_freq(carrier, srate, tone) ((s32)( \
         (compat_remainder(carrier + tone, srate)) / srate * 2 * INT_PI))

/*
 * We calculate the baseband frequencies of the carrier and the pilot tones
 * based on the sampling rate of the audio rds fifo.
 */

#define FREQ_A2_CARRIER         baseband_freq(54687.5, 2689.36, 0.0)
#define FREQ_A2_DUAL            baseband_freq(54687.5, 2689.36, 274.1)
#define FREQ_A2_STEREO          baseband_freq(54687.5, 2689.36, 117.5)

/*
 * The frequencies below are from the reference driver. They probably need
 * further adjustments, because they are not tested at all. You may even need
 * to play a bit with the registers of the chip to select the proper signal
 * for the input of the audio rds fifo, and measure it's sampling rate to
 * calculate the proper baseband frequencies...
 */

#define FREQ_A2M_CARRIER        ((s32)(2.114516 * 32768.0))
#define FREQ_A2M_DUAL           ((s32)(2.754916 * 32768.0))
#define FREQ_A2M_STEREO         ((s32)(2.462326 * 32768.0))

#define FREQ_EIAJ_CARRIER       ((s32)(1.963495 * 32768.0)) /* 5pi/8  */
#define FREQ_EIAJ_DUAL          ((s32)(2.562118 * 32768.0))
#define FREQ_EIAJ_STEREO        ((s32)(2.601053 * 32768.0))

#define FREQ_BTSC_DUAL          ((s32)(1.963495 * 32768.0)) /* 5pi/8  */
#define FREQ_BTSC_DUAL_REF      ((s32)(1.374446 * 32768.0)) /* 7pi/16 */

#define FREQ_BTSC_SAP           ((s32)(2.471532 * 32768.0))
#define FREQ_BTSC_SAP_REF       ((s32)(1.730072 * 32768.0))

/* The spectrum of the signal should be empty between these frequencies. */
#define FREQ_NOISE_START        ((s32)(0.100000 * 32768.0))
#define FREQ_NOISE_END          ((s32)(1.200000 * 32768.0))

static unsigned int dsp_debug;
module_param(dsp_debug, int, 0644);
MODULE_PARM_DESC(dsp_debug, "enable audio dsp debug messages");

#define dprintk(level, fmt, arg...) do {                                \
        if (dsp_debug >= level)                                         \
                printk(KERN_DEBUG pr_fmt("%s: dsp:" fmt),               \
                        __func__, ##arg);                               \
} while (0)

static s32 int_cos(u32 x)
{
        u32 t2, t4, t6, t8;
        s32 ret;
        u16 period = x / INT_PI;

        if (period % 2)
                return -int_cos(x - INT_PI);
        x = x % INT_PI;
        if (x > INT_PI / 2)
                return -int_cos(INT_PI / 2 - (x % (INT_PI / 2)));
        /*
         * Now x is between 0 and INT_PI/2.
         * To calculate cos(x) we use it's Taylor polinom.
         */
        t2 = x * x / 32768 / 2;
        t4 = t2 * x / 32768 * x / 32768 / 3 / 4;
        t6 = t4 * x / 32768 * x / 32768 / 5 / 6;
        t8 = t6 * x / 32768 * x / 32768 / 7 / 8;
        ret = 32768 - t2 + t4 - t6 + t8;
        return ret;
}

static u32 int_goertzel(s16 x[], u32 N, u32 freq)
{
        /*
         * We use the Goertzel algorithm to determine the power of the
         * given frequency in the signal
         */
        s32 s_prev = 0;
        s32 s_prev2 = 0;
        s32 coeff = 2 * int_cos(freq);
        u32 i;

        u64 tmp;
        u32 divisor;

        for (i = 0; i < N; i++) {
                s32 s = x[i] + ((s64)coeff * s_prev / 32768) - s_prev2;

                s_prev2 = s_prev;
                s_prev = s;
        }

        tmp = (s64)s_prev2 * s_prev2 + (s64)s_prev * s_prev -
                      (s64)coeff * s_prev2 * s_prev / 32768;

        /*
         * XXX: N must be low enough so that N*N fits in s32.
         * Else we need two divisions.
         */
        divisor = N * N;
        do_div(tmp, divisor);

        return (u32)tmp;
}

static u32 freq_magnitude(s16 x[], u32 N, u32 freq)
{
        u32 sum = int_goertzel(x, N, freq);

        return (u32)int_sqrt(sum);
}

static u32 noise_magnitude(s16 x[], u32 N, u32 freq_start, u32 freq_end)
{
        int i;
        u32 sum = 0;
        u32 freq_step;
        int samples = 5;

        if (N > 192) {
                /* The last 192 samples are enough for noise detection */
                x += (N - 192);
                N = 192;
        }

        freq_step = (freq_end - freq_start) / (samples - 1);

        for (i = 0; i < samples; i++) {
                sum += int_goertzel(x, N, freq_start);
                freq_start += freq_step;
        }

        return (u32)int_sqrt(sum / samples);
}

static s32 detect_a2_a2m_eiaj(struct cx88_core *core, s16 x[], u32 N)
{
        s32 carrier, stereo, dual, noise;
        s32 carrier_freq, stereo_freq, dual_freq;
        s32 ret;

        switch (core->tvaudio) {
        case WW_BG:
        case WW_DK:
                carrier_freq = FREQ_A2_CARRIER;
                stereo_freq = FREQ_A2_STEREO;
                dual_freq = FREQ_A2_DUAL;
                break;
        case WW_M:
                carrier_freq = FREQ_A2M_CARRIER;
                stereo_freq = FREQ_A2M_STEREO;
                dual_freq = FREQ_A2M_DUAL;
                break;
        case WW_EIAJ:
                carrier_freq = FREQ_EIAJ_CARRIER;
                stereo_freq = FREQ_EIAJ_STEREO;
                dual_freq = FREQ_EIAJ_DUAL;
                break;
        default:
                pr_warn("unsupported audio mode %d for %s\n",
                        core->tvaudio, __func__);
                return UNSET;
        }

        carrier = freq_magnitude(x, N, carrier_freq);
        stereo  = freq_magnitude(x, N, stereo_freq);
        dual    = freq_magnitude(x, N, dual_freq);
        noise   = noise_magnitude(x, N, FREQ_NOISE_START, FREQ_NOISE_END);

        dprintk(1,
                "detect a2/a2m/eiaj: carrier=%d, stereo=%d, dual=%d, noise=%d\n",
                carrier, stereo, dual, noise);

        if (stereo > dual)
                ret = V4L2_TUNER_SUB_STEREO;
        else
                ret = V4L2_TUNER_SUB_LANG1 | V4L2_TUNER_SUB_LANG2;

        if (core->tvaudio == WW_EIAJ) {
                /* EIAJ checks may need adjustments */
                if ((carrier > max(stereo, dual) * 2) &&
                    (carrier < max(stereo, dual) * 6) &&
                    (carrier > 20 && carrier < 200) &&
                    (max(stereo, dual) > min(stereo, dual))) {
                        /*
                         * For EIAJ the carrier is always present,
                         * so we probably don't need noise detection
                         */
                        return ret;
                }
        } else {
                if ((carrier > max(stereo, dual) * 2) &&
                    (carrier < max(stereo, dual) * 8) &&
                    (carrier > 20 && carrier < 200) &&
                    (noise < 10) &&
                    (max(stereo, dual) > min(stereo, dual) * 2)) {
                        return ret;
                }
        }
        return V4L2_TUNER_SUB_MONO;
}

static s32 detect_btsc(struct cx88_core *core, s16 x[], u32 N)
{
        s32 sap_ref = freq_magnitude(x, N, FREQ_BTSC_SAP_REF);
        s32 sap = freq_magnitude(x, N, FREQ_BTSC_SAP);
        s32 dual_ref = freq_magnitude(x, N, FREQ_BTSC_DUAL_REF);
        s32 dual = freq_magnitude(x, N, FREQ_BTSC_DUAL);

        dprintk(1, "detect btsc: dual_ref=%d, dual=%d, sap_ref=%d, sap=%d\n",
                dual_ref, dual, sap_ref, sap);
        /* FIXME: Currently not supported */
        return UNSET;
}

static s16 *read_rds_samples(struct cx88_core *core, u32 *N)
{
        const struct sram_channel *srch = &cx88_sram_channels[SRAM_CH27];
        s16 *samples;

        unsigned int i;
        unsigned int bpl = srch->fifo_size / AUD_RDS_LINES;
        unsigned int spl = bpl / 4;
        unsigned int sample_count = spl * (AUD_RDS_LINES - 1);

        u32 current_address = cx_read(srch->ptr1_reg);
        u32 offset = (current_address - srch->fifo_start + bpl);

        dprintk(1,
                "read RDS samples: current_address=%08x (offset=%08x), sample_count=%d, aud_intstat=%08x\n",
                current_address,
                current_address - srch->fifo_start, sample_count,
                cx_read(MO_AUD_INTSTAT));
        samples = kmalloc_objs(*samples, sample_count);
        if (!samples)
                return NULL;

        *N = sample_count;

        for (i = 0; i < sample_count; i++)  {
                offset = offset % (AUD_RDS_LINES * bpl);
                samples[i] = cx_read(srch->fifo_start + offset);
                offset += 4;
        }

        dprintk(2, "RDS samples dump: %*ph\n", sample_count, samples);

        return samples;
}

s32 cx88_dsp_detect_stereo_sap(struct cx88_core *core)
{
        s16 *samples;
        u32 N = 0;
        s32 ret = UNSET;

        /* If audio RDS fifo is disabled, we can't read the samples */
        if (!(cx_read(MO_AUD_DMACNTRL) & 0x04))
                return ret;
        if (!(cx_read(AUD_CTL) & EN_FMRADIO_EN_RDS))
                return ret;

        /* Wait at least 500 ms after an audio standard change */
        if (time_before(jiffies, core->last_change + msecs_to_jiffies(500)))
                return ret;

        samples = read_rds_samples(core, &N);

        if (!samples)
                return ret;

        switch (core->tvaudio) {
        case WW_BG:
        case WW_DK:
        case WW_EIAJ:
        case WW_M:
                ret = detect_a2_a2m_eiaj(core, samples, N);
                break;
        case WW_BTSC:
                ret = detect_btsc(core, samples, N);
                break;
        case WW_NONE:
        case WW_I:
        case WW_L:
        case WW_I2SPT:
        case WW_FM:
        case WW_I2SADC:
                break;
        }

        kfree(samples);

        if (ret != UNSET)
                dprintk(1, "stereo/sap detection result:%s%s%s\n",
                        (ret & V4L2_TUNER_SUB_MONO) ? " mono" : "",
                        (ret & V4L2_TUNER_SUB_STEREO) ? " stereo" : "",
                        (ret & V4L2_TUNER_SUB_LANG2) ? " dual" : "");

        return ret;
}
EXPORT_SYMBOL(cx88_dsp_detect_stereo_sap);