regmap: Support accelerated noinc operations

Several architectures have accelerated operations for MMIO
operations writing to a single register, such as writesb, writesw,
writesl, writesq, readsb, readsw, readsl and readsq but regmap
currently cannot use them because we have no hooks for providing
an accelerated noinc back-end for MMIO.

Solve this by providing reg_[read/write]_noinc callbacks for
the bus abstraction, so that the regmap-mmio bus can use this.

Currently I do not see a need to support this for custom regmaps
so it is only added to the bus.

Callbacks are passed a void * with the array of values and a
count which is the number of items of the byte chunk size for
the specific register width.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220816204832.265837-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 120 insertions, 3 deletions

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index e371acea7e0e..41ff9f18b6a3 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2129,6 +2129,99 @@ int regmap_raw_write(struct regmap *map, unsigned int reg,
 }
 EXPORT_SYMBOL_GPL(regmap_raw_write);
 
+static int regmap_noinc_readwrite(struct regmap *map, unsigned int reg,
+				  void *val, unsigned int val_len, bool write)
+{
+	size_t val_bytes = map->format.val_bytes;
+	size_t val_count = val_len / val_bytes;
+	unsigned int lastval;
+	u8 *u8p;
+	u16 *u16p;
+	u32 *u32p;
+#ifdef CONFIG_64BIT
+	u64 *u64p;
+#endif
+	int ret;
+	int i;
+
+	switch (val_bytes) {
+	case 1:
+		u8p = val;
+		if (write)
+			lastval = (unsigned int)u8p[val_count - 1];
+		break;
+	case 2:
+		u16p = val;
+		if (write)
+			lastval = (unsigned int)u16p[val_count - 1];
+		break;
+	case 4:
+		u32p = val;
+		if (write)
+			lastval = (unsigned int)u32p[val_count - 1];
+		break;
+#ifdef CONFIG_64BIT
+	case 8:
+		u64p = val;
+		if (write)
+			lastval = (unsigned int)u64p[val_count - 1];
+		break;
+#endif
+	default:
+		return -EINVAL;
+	}
+
+	/*
+	 * Update the cache with the last value we write, the rest is just
+	 * gone down in the hardware FIFO. We can't cache FIFOs. This makes
+	 * sure a single read from the cache will work.
+	 */
+	if (write) {
+		if (!map->cache_bypass && !map->defer_caching) {
+			ret = regcache_write(map, reg, lastval);
+			if (ret != 0)
+				return ret;
+			if (map->cache_only) {
+				map->cache_dirty = true;
+				return 0;
+			}
+		}
+		ret = map->bus->reg_noinc_write(map->bus_context, reg, val, val_count);
+	} else {
+		ret = map->bus->reg_noinc_read(map->bus_context, reg, val, val_count);
+	}
+
+	if (!ret && regmap_should_log(map)) {
+		dev_info(map->dev, "%x %s [", reg, write ? "<=" : "=>");
+		for (i = 0; i < val_len; i++) {
+			switch (val_bytes) {
+			case 1:
+				pr_cont("%x", u8p[i]);
+				break;
+			case 2:
+				pr_cont("%x", u16p[i]);
+				break;
+			case 4:
+				pr_cont("%x", u32p[i]);
+				break;
+#ifdef CONFIG_64BIT
+			case 8:
+				pr_cont("%llx", u64p[i]);
+				break;
+#endif
+			default:
+				break;
+			}
+			if (i == (val_len - 1))
+				pr_cont("]\n");
+			else
+				pr_cont(",");
+		}
+	}
+
+	return 0;
+}
+
 /**
  * regmap_noinc_write(): Write data from a register without incrementing the
  *			register number
@@ -2156,9 +2249,8 @@ int regmap_noinc_write(struct regmap *map, unsigned int reg,
 	size_t write_len;
 	int ret;
 
-	if (!map->write)
-		return -ENOTSUPP;
-
+	if (!map->write && !(map->bus && map->bus->reg_noinc_write))
+		return -EINVAL;
 	if (val_len % map->format.val_bytes)
 		return -EINVAL;
 	if (!IS_ALIGNED(reg, map->reg_stride))
@@ -2173,6 +2265,15 @@ int regmap_noinc_write(struct regmap *map, unsigned int reg,
 		goto out_unlock;
 	}
 
+	/*
+	 * Use the accelerated operation if we can. The val drops the const
+	 * typing in order to facilitate code reuse in regmap_noinc_readwrite().
+	 */
+	if (map->bus->reg_noinc_write) {
+		ret = regmap_noinc_readwrite(map, reg, (void *)val, val_len, true);
+		goto out_unlock;
+	}
+
 	while (val_len) {
 		if (map->max_raw_write && map->max_raw_write < val_len)
 			write_len = map->max_raw_write;
@@ -2943,6 +3044,22 @@ int regmap_noinc_read(struct regmap *map, unsigned int reg,
 		goto out_unlock;
 	}
 
+	/* Use the accelerated operation if we can */
+	if (map->bus->reg_noinc_read) {
+		/*
+		 * We have not defined the FIFO semantics for cache, as the
+		 * cache is just one value deep. Should we return the last
+		 * written value? Just avoid this by always reading the FIFO
+		 * even when using cache. Cache only will not work.
+		 */
+		if (map->cache_only) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+		ret = regmap_noinc_readwrite(map, reg, val, val_len, false);
+		goto out_unlock;
+	}
+
 	while (val_len) {
 		if (map->max_raw_read && map->max_raw_read < val_len)
 			read_len = map->max_raw_read;