[PATCH] regmap: support regmap_field_write() on non-readable fields

[Krzysztof Kozlowski]

Current implementation of regmap_field_write() performs an update of
register (read+write), therefore it ignores regmap read-restrictions and
is not suitable for write-only registers (e.g. interrupt clearing).

Extend regmap_field_write() and regmap_field_force_write() to check if
register is readable and only then perform an update.  In the other
case, it is expected that mask of field covers entire register thus a
full write is allowed.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>

---

Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
Cc: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
 drivers/base/regmap/regmap.c | 50 ++++++++++++++++++++++++++++++++++++
 include/linux/regmap.h       | 15 ++---------
 2 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 0caa5690c560..4d18a34f7b2c 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2192,6 +2192,56 @@ int regmap_noinc_write(struct regmap *map, unsigned int reg,
 }
 EXPORT_SYMBOL_GPL(regmap_noinc_write);
 
+static int _regmap_field_write_or_update(struct regmap_field *field,
+					 unsigned int val, bool *change,
+					 bool async, bool force)
+{
+	unsigned int mask = (~0 << field->shift) & field->mask;
+	unsigned int map_val_mask, map_val_mask_h;
+	int ret;
+
+	if (regmap_readable(field->regmap, field->reg))
+		return regmap_update_bits_base(field->regmap, field->reg,
+					       mask, val << field->shift,
+					       change, async, force);
+
+	map_val_mask_h = field->regmap->format.val_bytes * 8 - 1;
+	map_val_mask = GENMASK(map_val_mask_h, 0);
+
+	/* Writes of parts of register are not allowed for sanity */
+	if (field->shift)
+		return -EINVAL;
+
+	/* Mask of field must cover entire register */
+	if (field->mask != map_val_mask)
+		return -EINVAL;
+
+	if (change)
+		*change = false;
+
+	if (async)
+		ret = regmap_write(field->regmap, field->reg, val);
+	else
+		ret = regmap_write_async(field->regmap, field->reg, val);
+
+	if (ret == 0 && change)
+		*change = true;
+
+	return ret;
+}
+
+int regmap_field_write(struct regmap_field *field, unsigned int val)
+{
+	return _regmap_field_write_or_update(field, val, NULL, false, false);
+}
+EXPORT_SYMBOL_GPL(regmap_field_write);
+
+int regmap_field_force_write(struct regmap_field *field,  unsigned int val)
+{
+	return _regmap_field_write_or_update(field, val, NULL, false, true);
+}
+EXPORT_SYMBOL_GPL(regmap_field_force_write);
+
 /**
  * regmap_field_update_bits_base() - Perform a read/modify/write cycle a
  *                                   register field.
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 7cf2157134ac..08507e764dfa 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -1307,6 +1307,8 @@ void devm_regmap_field_bulk_free(struct device *dev,
 				 struct regmap_field *field);
 
 int regmap_field_read(struct regmap_field *field, unsigned int *val);
+int regmap_field_write(struct regmap_field *field, unsigned int val);
+int regmap_field_force_write(struct regmap_field *field,  unsigned int val);
 int regmap_field_update_bits_base(struct regmap_field *field,
 				  unsigned int mask, unsigned int val,
 				  bool *change, bool async, bool force);
@@ -1316,19 +1318,6 @@ int regmap_fields_update_bits_base(struct regmap_field *field,  unsigned int id,
 				   unsigned int mask, unsigned int val,
 				   bool *change, bool async, bool force);
 
-static inline int regmap_field_write(struct regmap_field *field,
-				     unsigned int val)
-{
-	return regmap_field_update_bits_base(field, ~0, val,
-					     NULL, false, false);
-}
-
-static inline int regmap_field_force_write(struct regmap_field *field,
-					   unsigned int val)
-{
-	return regmap_field_update_bits_base(field, ~0, val, NULL, false, true);
-}
-
 static inline int regmap_field_update_bits(struct regmap_field *field,
 					   unsigned int mask, unsigned int val)
 {
-- 
2.34.1