From 3ec66893e377b088c1284d2d23adb2aeea6d7965 Mon Sep 17 00:00:00 2001
From: Aidan MacDonald <amachronic@protonmail.com>
Date: Sat, 27 Feb 2021 22:08:58 +0000
Subject: New port: FiiO M3K on bare metal

Change-Id: I7517e7d5459e129dcfc9465c6fbd708619888fbe
---
 firmware/target/mips/ingenic_x1000/aic-x1000.c | 119 +++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 firmware/target/mips/ingenic_x1000/aic-x1000.c

(limited to 'firmware/target/mips/ingenic_x1000/aic-x1000.c')

diff --git a/firmware/target/mips/ingenic_x1000/aic-x1000.c b/firmware/target/mips/ingenic_x1000/aic-x1000.c
new file mode 100644
index 0000000000..a0e509d3b6
--- /dev/null
+++ b/firmware/target/mips/ingenic_x1000/aic-x1000.c
@@ -0,0 +1,119 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2021 Aidan MacDonald
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "system.h"
+#include "aic-x1000.h"
+#include "gpio-x1000.h"
+#include "x1000/aic.h"
+#include "x1000/cpm.h"
+
+/* Given a rational number m/n < 1, find its representation as a continued
+ * fraction [0; a1, a2, a3, ..., a_k]. At most "cnt" terms are calculated
+ * and written out to "buf". Returns the number of terms written; the result
+ * is complete if this value is less than "cnt", and may be incomplete if it
+ * is equal to "cnt". (Note the leading zero term is not written to "buf".)
+ */
+static unsigned cf_derive(unsigned m, unsigned n, unsigned* buf, unsigned cnt)
+{
+    unsigned wrote = 0;
+    unsigned a = m / n;
+    while(cnt--) {
+        unsigned tmp = n;
+        n = m - n * a;
+        if(n == 0)
+            break;
+
+        m = tmp;
+        a = m / n;
+        *buf++ = a;
+        wrote++;
+    }
+
+    return wrote;
+}
+
+/* Given a finite continued fraction [0; buf[0], buf[1], ..., buf[count-1]],
+ * calculate the rational number m/n which it represents. Returns m and n.
+ * If count is zero, then m and n are undefined.
+ */
+static void cf_expand(const unsigned* buf, unsigned count,
+                      unsigned* m, unsigned* n)
+{
+    if(count == 0)
+        return;
+
+    unsigned i = count - 1;
+    unsigned mx = 1, nx = buf[i];
+    while(i--) {
+        unsigned tmp = nx;
+        nx = mx + buf[i] * nx;
+        mx = tmp;
+    }
+
+    *m = mx;
+    *n = nx;
+}
+
+int aic_i2s_set_mclk(x1000_clk_t clksrc, unsigned fs, unsigned mult)
+{
+    /* get the input clock rate */
+    uint32_t src_freq = clk_get(clksrc);
+
+    /* reject invalid parameters */
+    if(mult % 64 != 0)
+        return -1;
+
+    if(clksrc == X1000_EXCLK_FREQ) {
+        if(mult != 0)
+            return -1;
+
+        jz_writef(AIC_I2SCR, STPBK(1));
+        jz_writef(CPM_I2SCDR, CS(0), CE(0));
+        REG_AIC_I2SDIV = X1000_EXCLK_FREQ / 64 / fs;
+    } else {
+        if(mult == 0)
+            return -1;
+        if(fs*mult > src_freq)
+            return -1;
+
+        /* calculate best rational approximation that fits our constraints */
+        unsigned m = 0, n = 0;
+        unsigned buf[16];
+        unsigned cnt = cf_derive(fs*mult, src_freq, &buf[0], 16);
+        do {
+            cf_expand(&buf[0], cnt, &m, &n);
+            cnt -= 1;
+        } while(cnt > 0 && (m > 512 || n > 8192) && (n >= 2*m));
+
+        /* wrong values */
+        if(cnt == 0 || n == 0 || m == 0)
+            return -1;
+
+        jz_writef(AIC_I2SCR, STPBK(1));
+        jz_writef(CPM_I2SCDR, PCS(clksrc == X1000_CLK_MPLL ? 1 : 0),
+                  CS(1), CE(1), DIV_M(m), DIV_N(n));
+        jz_write(CPM_I2SCDR1, REG_CPM_I2SCDR1);
+        REG_AIC_I2SDIV = (mult / 64) - 1;
+    }
+
+    jz_writef(AIC_I2SCR, STPBK(0));
+    return 0;
+}
-- 
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