ASoC: core: Add signed register volume control logic

Some codecs use signed volume control representation with non standard
register sizes, e.g. 6 or 7 bit signed integers.

This patch adds generic signed register volume control logic to
soc-core. Instead of a fixed width signed register control, this
implementation uses a 'min' value and the signed bit location to translate
it to an absolute volume. Using the 'sign_bit' we can calculate a
correct mask for the register values and translate it back into signed
integers of standard size.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
(cherry picked from commit f227b88f0fce5f9b82aa934f8829a741c2e06d82)

1 files changed, 61 insertions, 7 deletions

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index d56bbea6e75e..2192e69469b1 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2603,6 +2603,48 @@ int snd_soc_info_volsw_ext(struct snd_kcontrol *kcontrol,
 EXPORT_SYMBOL_GPL(snd_soc_info_volsw_ext);
 
 /**
+ * snd_soc_read_signed - Read a codec register and interprete as signed value
+ * @codec: codec
+ * @reg: Register to read
+ * @mask: Mask to use after shifting the register value
+ * @shift: Right shift of register value
+ * @sign_bit: Bit that describes if a number is negative or not.
+ *
+ * This functions reads a codec register. The register value is shifted right
+ * by 'shift' bits and masked with the given 'mask'. Afterwards it translates
+ * the given registervalue into a signed integer if sign_bit is non-zero.
+ *
+ * Returns the register value as signed int.
+ */
+static int snd_soc_read_signed(struct snd_soc_codec *codec, unsigned int reg,
+                unsigned int mask, unsigned int shift, unsigned int sign_bit)
+{
+        int ret;
+        unsigned int val;
+
+        val = (snd_soc_read(codec, reg) >> shift) & mask;
+
+        if (!sign_bit)
+                return val;
+
+        /* non-negative number */
+        if (!(val & BIT(sign_bit)))
+                return val;
+
+        ret = val;
+
+        /*
+         * The register most probably does not contain a full-sized int.
+         * Instead we have an arbitrary number of bits in a signed
+         * representation which has to be translated into a full-sized int.
+         * This is done by filling up all bits above the sign-bit.
+         */
+        ret |= ~((int)(BIT(sign_bit) - 1));
+
+        return ret;
+}
+
+/**
  * snd_soc_info_volsw - single mixer info callback
  * @kcontrol: mixer control
  * @uinfo: control element information
@@ -2630,7 +2672,7 @@ int snd_soc_info_volsw(struct snd_kcontrol *kcontrol,
 
         uinfo->count = snd_soc_volsw_is_stereo(mc) ? 2 : 1;
         uinfo->value.integer.min = 0;
-        uinfo->value.integer.max = platform_max;
+        uinfo->value.integer.max = platform_max - mc->min;
         return 0;
 }
 EXPORT_SYMBOL_GPL(snd_soc_info_volsw);
@@ -2656,11 +2698,16 @@ int snd_soc_get_volsw(struct snd_kcontrol *kcontrol,
         unsigned int shift = mc->shift;
         unsigned int rshift = mc->rshift;
         int max = mc->max;
+        int min = mc->min;
+        int sign_bit = mc->sign_bit;
         unsigned int mask = (1 << fls(max)) - 1;
         unsigned int invert = mc->invert;
 
-        ucontrol->value.integer.value[0] =
-                (snd_soc_read(codec, reg) >> shift) & mask;
+        if (sign_bit)
+                mask = BIT(sign_bit + 1) - 1;
+
+        ucontrol->value.integer.value[0] = snd_soc_read_signed(codec, reg, mask,
+                        shift, sign_bit) - min;
         if (invert)
                 ucontrol->value.integer.value[0] =
                         max - ucontrol->value.integer.value[0];
@@ -2668,10 +2715,12 @@ int snd_soc_get_volsw(struct snd_kcontrol *kcontrol,
         if (snd_soc_volsw_is_stereo(mc)) {
                 if (reg == reg2)
                         ucontrol->value.integer.value[1] =
-                                (snd_soc_read(codec, reg) >> rshift) & mask;
+                                snd_soc_read_signed(codec, reg, mask, rshift,
+                                                sign_bit) - min;
                 else
                         ucontrol->value.integer.value[1] =
-                                (snd_soc_read(codec, reg2) >> shift) & mask;
+                                snd_soc_read_signed(codec, reg2, mask, shift,
+                                                sign_bit) - min;
                 if (invert)
                         ucontrol->value.integer.value[1] =
                                 max - ucontrol->value.integer.value[1];
@@ -2702,6 +2751,8 @@ int snd_soc_put_volsw(struct snd_kcontrol *kcontrol,
         unsigned int shift = mc->shift;
         unsigned int rshift = mc->rshift;
         int max = mc->max;
+        int min = mc->min;
+        unsigned int sign_bit = mc->sign_bit;
         unsigned int mask = (1 << fls(max)) - 1;
         unsigned int invert = mc->invert;
         int err;
@@ -2709,13 +2760,16 @@ int snd_soc_put_volsw(struct snd_kcontrol *kcontrol,
         unsigned int val2 = 0;
         unsigned int val, val_mask;
 
-        val = (ucontrol->value.integer.value[0] & mask);
+        if (sign_bit)
+                mask = BIT(sign_bit + 1) - 1;
+
+        val = ((ucontrol->value.integer.value[0] + min) & mask);
         if (invert)
                 val = max - val;
         val_mask = mask << shift;
         val = val << shift;
         if (snd_soc_volsw_is_stereo(mc)) {
-                val2 = (ucontrol->value.integer.value[1] & mask);
+                val2 = ((ucontrol->value.integer.value[1] + min) & mask);
                 if (invert)
                         val2 = max - val2;
                 if (reg == reg2) {