regmap: spi: Set regmap max raw r/w from max_transfer_size

Set regmap raw read/write from spi max_transfer_size
so regmap_raw_read/write can split the access into chunks

Signed-off-by: Lucas Tanure <tanureal@opensource.cirrus.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
[André: fix build warning]
Signed-off-by: André Almeida <andrealmeid@collabora.com>
Link: https://lore.kernel.org/r/20211021132721.13669-1-andrealmeid@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Lucas Tanure

drivers/base/regmap/regmap-spi.c

@@ -109,13 +109,37 @@ static const struct regmap_bus regmap_spi = {
 	.val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
+static const struct regmap_bus *regmap_get_spi_bus(struct spi_device *spi,
+						   const struct regmap_config *config)
+{
+	size_t max_size = spi_max_transfer_size(spi);
+	struct regmap_bus *bus;
+
+	if (max_size != SIZE_MAX) {
+		bus = kmemdup(&regmap_spi, sizeof(*bus), GFP_KERNEL);
+		if (!bus)
+			return ERR_PTR(-ENOMEM);
+
+		bus->free_on_exit = true;
+		bus->max_raw_read = max_size;
+		bus->max_raw_write = max_size;
+		return bus;
+	}
+
+	return &regmap_spi;
+}
+
 struct regmap *__regmap_init_spi(struct spi_device *spi,
 				 const struct regmap_config *config,
 				 struct lock_class_key *lock_key,
 				 const char *lock_name)
 {
-	return __regmap_init(&spi->dev, &regmap_spi, &spi->dev, config,
-			     lock_key, lock_name);
+	const struct regmap_bus *bus = regmap_get_spi_bus(spi, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __regmap_init(&spi->dev, bus, &spi->dev, config, lock_key, lock_name);
 }
 EXPORT_SYMBOL_GPL(__regmap_init_spi);
 
@@ -124,8 +148,12 @@ struct regmap *__devm_regmap_init_spi(struct spi_device *spi,
 				      struct lock_class_key *lock_key,
 				      const char *lock_name)
 {
-	return __devm_regmap_init(&spi->dev, &regmap_spi, &spi->dev, config,
-				  lock_key, lock_name);
+	const struct regmap_bus *bus = regmap_get_spi_bus(spi, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __devm_regmap_init(&spi->dev, bus, &spi->dev, config, lock_key, lock_name);
 }
 EXPORT_SYMBOL_GPL(__devm_regmap_init_spi);