[PATCH 1/2] ASoC: tegra210_adx: simplify byte map get/put logic

[Piyush Patle <piyushpatle228@gmail.com>]

The byte-map controls ("Byte Map N") already expose a value range of
[0, 256] to userspace via SOC_SINGLE_EXT(), where 256 is the
"disabled" sentinel. The driver stored this state as a byte-packed
u32 map[] array plus a separate byte_mask[] bitmap tracking which
slots were enabled, because 256 does not fit in a byte. As a result
get_byte_map() had to consult byte_mask[] to decide whether to
report the stored byte or 256, and put_byte_map() had to keep the
two arrays in sync on every write.

Store each slot as a u16 holding the control value directly
(0..255 enabled, 256 disabled). This is the native representation
for what userspace already sees, so get_byte_map() becomes a direct
return and put_byte_map() becomes a compare-and-store. The
hardware-facing packed RAM word and the IN_BYTE_EN mask are now
derived on the fly inside tegra210_adx_write_map_ram() from the
slot array, which is the only place that needs to know about the
hardware layout. This also lets us drop the byte_mask field from
struct tegra210_adx.

Slots are initialised to 256 in probe() so the default reported
value stays "disabled", matching previous behaviour. Values written
from userspace that fall outside [0, 255] are clamped to 256
("disabled") exactly as before -- no userspace-visible change.

As a side effect this also fixes a latent bug in the previous
put_byte_map(): because it compared the enable mask rather than the
stored byte, changing a slot from one enabled value to another
enabled value (e.g. 42 -> 99) would early-return without persisting
the new value.

Also fix a potential undefined behavior when constructing the packed
RAM word by ensuring the shift operates on a u32 value.

Addresses TODO left in tegra210_adx_get_byte_map().

Signed-off-by: Piyush Patle <piyushpatle228@gmail.com>
---
 sound/soc/tegra/tegra210_adx.c | 80 ++++++++++++++++------------------
 sound/soc/tegra/tegra210_adx.h |  5 ++-
 2 files changed, 40 insertions(+), 45 deletions(-)

diff --git a/sound/soc/tegra/tegra210_adx.c b/sound/soc/tegra/tegra210_adx.c
index 95875c75ddf8..67948459e884 100644
--- a/sound/soc/tegra/tegra210_adx.c
+++ b/sound/soc/tegra/tegra210_adx.c
@@ -47,6 +47,7 @@ static const struct reg_default tegra264_adx_reg_defaults[] = {
 
 static void tegra210_adx_write_map_ram(struct tegra210_adx *adx)
 {
+	unsigned int byte_mask[TEGRA264_ADX_BYTE_MASK_COUNT] = { 0 };
 	int i;
 
 	regmap_write(adx->regmap, TEGRA210_ADX_CFG_RAM_CTRL +
@@ -55,15 +56,28 @@ static void tegra210_adx_write_map_ram(struct tegra210_adx *adx)
 		     TEGRA210_ADX_CFG_RAM_CTRL_ADDR_INIT_EN |
 		     TEGRA210_ADX_CFG_RAM_CTRL_RW_WRITE);
 
-	for (i = 0; i < adx->soc_data->ram_depth; i++)
+	for (i = 0; i < adx->soc_data->ram_depth; i++) {
+		u32 word = 0;
+		int b;
+
+		for (b = 0; b < 4; b++) {
+			unsigned int slot = i * 4 + b;
+			u16 val = adx->map[slot];
+
+			if (val >= 256)
+				continue;
+
+			word |= (u32)val << (b * 8);
+			byte_mask[slot / 32] |= 1U << (slot % 32);
+		}
 		regmap_write(adx->regmap, TEGRA210_ADX_CFG_RAM_DATA +
-				adx->soc_data->cya_offset,
-			     adx->map[i]);
+				adx->soc_data->cya_offset, word);
+	}
 
 	for (i = 0; i < adx->soc_data->byte_mask_size; i++)
 		regmap_write(adx->regmap,
 			     TEGRA210_ADX_IN_BYTE_EN0 + (i * TEGRA210_ADX_AUDIOCIF_CH_STRIDE),
-			     adx->byte_mask[i]);
+			     byte_mask[i]);
 }
 
 static int tegra210_adx_startup(struct snd_pcm_substream *substream,
@@ -188,27 +202,10 @@ static int tegra210_adx_get_byte_map(struct snd_kcontrol *kcontrol,
 {
 	struct snd_soc_component *cmpnt = snd_kcontrol_chip(kcontrol);
 	struct tegra210_adx *adx = snd_soc_component_get_drvdata(cmpnt);
-	struct soc_mixer_control *mc;
-	unsigned char *bytes_map = (unsigned char *)adx->map;
-	int enabled;
+	struct soc_mixer_control *mc =
+		(struct soc_mixer_control *)kcontrol->private_value;
 
-	mc = (struct soc_mixer_control *)kcontrol->private_value;
-	enabled = adx->byte_mask[mc->reg / 32] & (1 << (mc->reg % 32));
-
-	/*
-	 * TODO: Simplify this logic to just return from bytes_map[]
-	 *
-	 * Presently below is required since bytes_map[] is
-	 * tightly packed and cannot store the control value of 256.
-	 * Byte mask state is used to know if 256 needs to be returned.
-	 * Note that for control value of 256, the put() call stores 0
-	 * in the bytes_map[] and disables the corresponding bit in
-	 * byte_mask[].
-	 */
-	if (enabled)
-		ucontrol->value.integer.value[0] = bytes_map[mc->reg];
-	else
-		ucontrol->value.integer.value[0] = 256;
+	ucontrol->value.integer.value[0] = adx->map[mc->reg];
 
 	return 0;
 }
@@ -218,23 +215,22 @@ static int tegra210_adx_put_byte_map(struct snd_kcontrol *kcontrol,
 {
 	struct snd_soc_component *cmpnt = snd_kcontrol_chip(kcontrol);
 	struct tegra210_adx *adx = snd_soc_component_get_drvdata(cmpnt);
-	unsigned char *bytes_map = (unsigned char *)adx->map;
-	int value = ucontrol->value.integer.value[0];
 	struct soc_mixer_control *mc =
 		(struct soc_mixer_control *)kcontrol->private_value;
-	unsigned int mask_val = adx->byte_mask[mc->reg / 32];
+	unsigned int value = ucontrol->value.integer.value[0];
 
-	if (value >= 0 && value <= 255)
-		mask_val |= (1 << (mc->reg % 32));
-	else
-		mask_val &= ~(1 << (mc->reg % 32));
+	/*
+	 * Match the previous behaviour: any value outside [0, 255] is
+	 * treated as the "disabled" sentinel (256). Negative values from
+	 * userspace fold in through the unsigned cast and are caught here.
+	 */
+	if (value > 255)
+		value = 256;
 
-	if (mask_val == adx->byte_mask[mc->reg / 32])
+	if (adx->map[mc->reg] == value)
 		return 0;
 
-	/* Update byte map and slot */
-	bytes_map[mc->reg] = value % 256;
-	adx->byte_mask[mc->reg / 32] = mask_val;
+	adx->map[mc->reg] = value;
 
 	return 1;
 }
@@ -675,7 +671,7 @@ static int tegra210_adx_platform_probe(struct platform_device *pdev)
 	const struct of_device_id *match;
 	struct tegra210_adx_soc_data *soc_data;
 	void __iomem *regs;
-	int err;
+	int err, i;
 
 	adx = devm_kzalloc(dev, sizeof(*adx), GFP_KERNEL);
 	if (!adx)
@@ -700,16 +696,14 @@ static int tegra210_adx_platform_probe(struct platform_device *pdev)
 
 	regcache_cache_only(adx->regmap, true);
 
-	adx->map = devm_kzalloc(dev, soc_data->ram_depth * sizeof(*adx->map),
-				GFP_KERNEL);
+	adx->map = devm_kcalloc(dev, soc_data->ram_depth * 4,
+				sizeof(*adx->map), GFP_KERNEL);
 	if (!adx->map)
 		return -ENOMEM;
 
-	adx->byte_mask = devm_kzalloc(dev,
-				      soc_data->byte_mask_size * sizeof(*adx->byte_mask),
-				      GFP_KERNEL);
-	if (!adx->byte_mask)
-		return -ENOMEM;
+	/* Initialize all byte map slots as disabled (value 256). */
+	for (i = 0; i < soc_data->ram_depth * 4; i++)
+		adx->map[i] = 256;
 
 	tegra210_adx_dais[TEGRA_ADX_IN_DAI_ID].playback.channels_max =
 			adx->soc_data->max_ch;
diff --git a/sound/soc/tegra/tegra210_adx.h b/sound/soc/tegra/tegra210_adx.h
index 176a4e40de0a..afe95e45458f 100644
--- a/sound/soc/tegra/tegra210_adx.h
+++ b/sound/soc/tegra/tegra210_adx.h
@@ -8,6 +8,8 @@
 #ifndef __TEGRA210_ADX_H__
 #define __TEGRA210_ADX_H__
 
+#include <linux/types.h>
+
 /* Register offsets from TEGRA210_ADX*_BASE */
 #define TEGRA210_ADX_RX_STATUS		0x0c
 #define TEGRA210_ADX_RX_INT_STATUS	0x10
@@ -88,8 +90,7 @@ struct tegra210_adx_soc_data {
 
 struct tegra210_adx {
 	struct regmap *regmap;
-	unsigned int *map;
-	unsigned int *byte_mask;
+	u16 *map;
 	const struct tegra210_adx_soc_data *soc_data;
 };
 
-- 
2.34.1