Audio: MFCC: Fix FFT buffer fill for 32-bit mode

When MFCC_FFT_BITS is 32, the HiFi3/4 mfcc_fill_fft_buffer() used
AE_S16_0_XP to write 16-bit samples into 32-bit icomplex32 containers.
This left the upper 16 bits of .real with stale data and .imag unzeroed,
causing corrupted FFT input after the first frame when scratch buffers
are reused for power_spectra and mel_log_32.

Replace all platform-specific implementations with a single generic C
version in mfcc_common.c. The function performs only data copying with
no arithmetic, so HiFi intrinsics provide very little benefit. The new
implementation uses int32_t pointer type with matching element stride,
and relies on the caller's bzero of fft_buf to keep imaginary parts
zero.

Fix mel_log_32 scratch space check to use fft_buffer_size instead of
assuming sizeof(icomplex32) per element, which overestimated available
space by 2x.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

Author: singalsu

src/audio/mfcc/mfcc_common.c

@@ -178,6 +178,53 @@ static int mfcc_stft_process(const struct comp_dev *dev, struct mfcc_comp_data *
 	return cc_count;
 }
 
+void mfcc_fill_fft_buffer(struct mfcc_state *state)
+{
+	struct mfcc_buffer *buf = &state->buf;
+	struct mfcc_fft *fft = &state->fft;
+	int32_t *d = &fft->fft_buf[fft->fft_fill_start_idx].real;
+	const int fft_elem_inc = sizeof(fft->fft_buf[0]) / sizeof(int32_t);
+	int16_t *prev = state->prev_data;
+	int16_t *prev_end = prev + state->prev_data_size;
+	int16_t *r = buf->r_ptr;
+	int copied;
+	int nmax;
+	int n;
+	int j;
+
+	/* Copy overlapped samples from state buffer. The fft_buf has been
+	 * cleared by caller so imaginary part remains zero.
+	 */
+	while (prev < prev_end) {
+		*d = *prev++;
+		d += fft_elem_inc;
+	}
+
+	/* Copy hop size of new data from circular buffer */
+	for (copied = 0; copied < fft->fft_hop_size; copied += n) {
+		nmax = fft->fft_hop_size - copied;
+		n = mfcc_buffer_samples_without_wrap(buf, r);
+		n = MIN(n, nmax);
+		for (j = 0; j < n; j++) {
+			*d = *r++;
+			d += fft_elem_inc;
+		}
+		r = mfcc_buffer_wrap(buf, r);
+	}
+
+	buf->s_avail -= copied;
+	buf->s_free += copied;
+	buf->r_ptr = r;
+
+	/* Copy for next time data back to overlap buffer */
+	d = (int32_t *)&fft->fft_buf[fft->fft_fill_start_idx + fft->fft_hop_size].real;
+	prev = state->prev_data;
+	while (prev < prev_end) {
+		*prev++ = *d;
+		d += fft_elem_inc;
+	}
+}
+
 #if CONFIG_FORMAT_S16LE
 static int16_t *mfcc_sink_copy_zero_s16(const struct audio_stream *sink, int16_t *w_ptr,
 					int samples)

src/audio/mfcc/mfcc_generic.c

@@ -51,47 +51,6 @@ void mfcc_fill_prev_samples(struct mfcc_buffer *buf, int16_t *prev_data,
 	buf->r_ptr = r;
 }
 
-void mfcc_fill_fft_buffer(struct mfcc_state *state)
-{
-	struct mfcc_buffer *buf = &state->buf;
-	struct mfcc_fft *fft = &state->fft;
-	int16_t *r = buf->r_ptr;
-	int copied;
-	int nmax;
-	int idx = fft->fft_fill_start_idx;
-	int j;
-	int n;
-
-	/* Copy overlapped samples from state buffer. Imaginary part of input
-	 * remains zero.
-	 */
-	for (j = 0; j < state->prev_data_size; j++)
-		fft->fft_buf[idx + j].real = state->prev_data[j];
-
-	/* Copy hop size of new data from circular buffer */
-	idx += state->prev_data_size;
-	for (copied = 0; copied < fft->fft_hop_size; copied += n) {
-		nmax = fft->fft_hop_size - copied;
-		n = mfcc_buffer_samples_without_wrap(buf, r);
-		n = MIN(n, nmax);
-		for (j = 0; j < n; j++) {
-			fft->fft_buf[idx].real = *r;
-			r++;
-			idx++;
-		}
-		r = mfcc_buffer_wrap(buf, r);
-	}
-
-	buf->s_avail -= copied;
-	buf->s_free += copied;
-	buf->r_ptr = r;
-
-	/* Copy for next time data back to overlap buffer */
-	idx = fft->fft_fill_start_idx + fft->fft_hop_size;
-	for (j = 0; j < state->prev_data_size; j++)
-		state->prev_data[j] = fft->fft_buf[idx + j].real;
-}
-
 void mfcc_apply_window(struct mfcc_state *state, int input_shift)
 {
 	struct mfcc_fft *fft = &state->fft;

src/audio/mfcc/mfcc_hifi3.c

@@ -128,50 +128,6 @@ void mfcc_fill_prev_samples(struct mfcc_buffer *buf, int16_t *prev_data,
 	buf->r_ptr = (void *)in; /* int16_t pointer but direct cast is not possible */
 }
 
-void mfcc_fill_fft_buffer(struct mfcc_state *state)
-{
-	struct mfcc_buffer *buf = &state->buf;
-	struct mfcc_fft *fft = &state->fft;
-	int idx = fft->fft_fill_start_idx;
-	ae_int16 *out = (ae_int16 *)&fft->fft_buf[idx].real;
-	ae_int16 *in = (ae_int16 *)state->prev_data;
-	ae_int16x4 sample;
-	const int buf_inc = sizeof(ae_int16);
-	const int fft_inc = sizeof(fft->fft_buf[0]);
-	int j;
-
-	/* Copy overlapped samples from state buffer. Imaginary part of input
-	 * remains zero.
-	 */
-	for (j = 0; j < state->prev_data_size; j++) {
-		AE_L16_XP(sample, in, buf_inc);
-		AE_S16_0_XP(sample, out, fft_inc);
-	}
-
-	/* Copy hop size of new data from circular buffer */
-	idx += state->prev_data_size;
-	in = (ae_int16 *)buf->r_ptr;
-	out = (ae_int16 *)&fft->fft_buf[idx].real;
-	set_circular_buf0(buf->addr, buf->end_addr);
-	for (j = 0; j < fft->fft_hop_size; j++) {
-		AE_L16_XC(sample, in, buf_inc);
-		AE_S16_0_XP(sample, out, fft_inc);
-	}
-
-	buf->s_avail -= fft->fft_hop_size;
-	buf->s_free += fft->fft_hop_size;
-	buf->r_ptr = (int16_t *)in;
-
-	/* Copy for next time data back to overlap buffer */
-	idx = fft->fft_fill_start_idx + fft->fft_hop_size;
-	in = (ae_int16 *)&fft->fft_buf[idx].real;
-	out = (ae_int16 *)state->prev_data;
-	for (j = 0; j < state->prev_data_size; j++) {
-		AE_L16_XP(sample, in, fft_inc);
-		AE_S16_0_XP(sample, out, buf_inc);
-	}
-}
-
 void mfcc_apply_window(struct mfcc_state *state, int input_shift)
 {
 	struct mfcc_fft *fft = &state->fft;

src/audio/mfcc/mfcc_hifi4.c

@@ -124,50 +124,6 @@ void mfcc_fill_prev_samples(struct mfcc_buffer *buf, int16_t *prev_data,
 	buf->r_ptr = (int16_t *)in;
 }
 
-void mfcc_fill_fft_buffer(struct mfcc_state *state)
-{
-	struct mfcc_buffer *buf = &state->buf;
-	struct mfcc_fft *fft = &state->fft;
-	int idx = fft->fft_fill_start_idx;
-	ae_int16 *out = (ae_int16 *)&fft->fft_buf[idx].real;
-	ae_int16 *in = (ae_int16 *)state->prev_data;
-	ae_int16x4 sample;
-	const int buf_inc = sizeof(ae_int16);
-	const int fft_inc = sizeof(fft->fft_buf[0]);
-	int j;
-
-	/* Copy overlapped samples from state buffer. Imaginary part of input
-	 * remains zero.
-	 */
-	for (j = 0; j < state->prev_data_size; j++) {
-		AE_L16_XP(sample, in, buf_inc);
-		AE_S16_0_XP(sample, out, fft_inc);
-	}
-
-	/* Copy hop size of new data from circular buffer */
-	idx += state->prev_data_size;
-	in = (ae_int16 *)buf->r_ptr;
-	out = (ae_int16 *)&fft->fft_buf[idx].real;
-	set_circular_buf0(buf->addr, buf->end_addr);
-	for (j = 0; j < fft->fft_hop_size; j++) {
-		AE_L16_XC(sample, in, buf_inc);
-		AE_S16_0_XP(sample, out, fft_inc);
-	}
-
-	buf->s_avail -= fft->fft_hop_size;
-	buf->s_free += fft->fft_hop_size;
-	buf->r_ptr = (int16_t *)in;
-
-	/* Copy for next time data back to overlap buffer */
-	idx = fft->fft_fill_start_idx + fft->fft_hop_size;
-	in = (ae_int16 *)&fft->fft_buf[idx].real;
-	out = (ae_int16 *)state->prev_data;
-	for (j = 0; j < state->prev_data_size; j++) {
-		AE_L16_XP(sample, in, fft_inc);
-		AE_S16_0_XP(sample, out, buf_inc);
-	}
-}
-
 void mfcc_apply_window(struct mfcc_state *state, int input_shift)
 {
 	struct mfcc_fft *fft = &state->fft;

src/audio/mfcc/mfcc_setup.c

@@ -304,7 +304,7 @@ int mfcc_setup(struct processing_module *mod, int max_frames, int sample_rate, i
 	state->mel_log_32 = &state->power_spectra[fft->half_fft_size];
 
 	/* Check that mel_log_32 fits in the remaining fft_buf scratch space */
-	int mel_log_32_space = fft->fft_padded_size * 2 - fft->half_fft_size;
+	int mel_log_32_space = (int)(fft->fft_buffer_size / sizeof(int32_t)) - fft->half_fft_size;
 
 	if (config->num_mel_bins > mel_log_32_space) {
 		comp_err(dev, "num_mel_bins %d exceeds mel_log_32 scratch space %d",