regmap: ram: support noinc semantics

Support noinc semantics in RAM backed regmaps, for testing purposes. Add
a new callback that selects registers which should have noinc behavior.
Bulk writes to a noinc register will cause the last value in the buffer
to be assigned to the register, while bulk reads will copy the same
value repeatedly into the buffer.

This patch only adds support to regmap-raw-ram, since regmap-ram does
not support bulk operations.

Signed-off-by: Ben Wolsieffer <ben.wolsieffer@hefring.com>
Link: https://lore.kernel.org/r/20231102203039.3069305-1-ben.wolsieffer@hefring.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: lopsided98

drivers/base/regmap/internal.h

@@ -318,6 +318,7 @@ struct regmap_ram_data {
 	bool *read;
 	bool *written;
 	enum regmap_endian reg_endian;
+	bool (*noinc_reg)(struct regmap_ram_data *data, unsigned int reg);
 };
 
 /*

drivers/base/regmap/regmap-raw-ram.c

@@ -41,10 +41,15 @@ static int regmap_raw_ram_gather_write(void *context,
 		return -EINVAL;
 
 	r = decode_reg(data->reg_endian, reg);
-	memcpy(&our_buf[r], val, val_len);
-
-	for (i = 0; i < val_len / 2; i++)
-		data->written[r + i] = true;
+	if (data->noinc_reg && data->noinc_reg(data, r)) {
+		memcpy(&our_buf[r], val + val_len - 2, 2);
+		data->written[r] = true;
+	} else {
+		memcpy(&our_buf[r], val, val_len);
+
+		for (i = 0; i < val_len / 2; i++)
+			data->written[r + i] = true;
+	}
 
 	return 0;
 }
@@ -70,10 +75,16 @@ static int regmap_raw_ram_read(void *context,
 		return -EINVAL;
 
 	r = decode_reg(data->reg_endian, reg);
-	memcpy(val, &our_buf[r], val_len);
-
-	for (i = 0; i < val_len / 2; i++)
-		data->read[r + i] = true;
+	if (data->noinc_reg && data->noinc_reg(data, r)) {
+		for (i = 0; i < val_len; i += 2)
+			memcpy(val + i, &our_buf[r], 2);
+		data->read[r] = true;
+	} else {
+		memcpy(val, &our_buf[r], val_len);
+
+		for (i = 0; i < val_len / 2; i++)
+			data->read[r + i] = true;
+	}
 
 	return 0;
 }