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Message-Id: <20220725141036.2399822-1-linus.walleij@linaro.org>
Date: Mon, 25 Jul 2022 16:10:35 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Mark Brown <broonie@...nel.org>
Cc: linux-kernel@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 1/2 v2] 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@...aro.org>
---
ChangeLog v1->v2:
- Factor out and reuse the code to format and read or write a
buffer of data to a noinc register at the cost of dropping
const from the buffer pointer in the write call. This is a
deadly sin in Rust and therefore impossible, but hey, this is
C, and dropping a const is a lesser evil than not being
able to reuse code.
---
drivers/base/regmap/regmap.c | 120 ++++++++++++++++++++++++++++++++++-
include/linux/regmap.h | 8 +++
2 files changed, 127 insertions(+), 1 deletion(-)
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 2221d9863831..16461b768f77 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2128,6 +2128,99 @@ 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
@@ -2157,7 +2250,7 @@ int regmap_noinc_write(struct regmap *map, unsigned int reg,
if (!map->bus)
return -EINVAL;
- if (!map->bus->write)
+ if (!map->bus->write && !map->bus->reg_noinc_write)
return -ENOTSUPP;
if (val_len % map->format.val_bytes)
return -EINVAL;
@@ -2173,6 +2266,15 @@ 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;
@@ -2918,6 +3020,22 @@ 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;
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 8952fa3d0d59..c60bd3a4b098 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -489,8 +489,12 @@ typedef int (*regmap_hw_read)(void *context,
void *val_buf, size_t val_size);
typedef int (*regmap_hw_reg_read)(void *context, unsigned int reg,
unsigned int *val);
+typedef int (*regmap_hw_reg_noinc_read)(void *context, unsigned int reg,
+ void *val, size_t val_count);
typedef int (*regmap_hw_reg_write)(void *context, unsigned int reg,
unsigned int val);
+typedef int (*regmap_hw_reg_noinc_write)(void *context, unsigned int reg,
+ const void *val, size_t val_count);
typedef int (*regmap_hw_reg_update_bits)(void *context, unsigned int reg,
unsigned int mask, unsigned int val);
typedef struct regmap_async *(*regmap_hw_async_alloc)(void);
@@ -511,6 +515,8 @@ typedef void (*regmap_hw_free_context)(void *context);
* must serialise with respect to non-async I/O.
* @reg_write: Write a single register value to the given register address. This
* write operation has to complete when returning from the function.
+ * @reg_write_noinc: Write multiple register value to the same register. This
+ * write operation has to complete when returning from the function.
* @reg_update_bits: Update bits operation to be used against volatile
* registers, intended for devices supporting some mechanism
* for setting clearing bits without having to
@@ -538,9 +544,11 @@ struct regmap_bus {
regmap_hw_gather_write gather_write;
regmap_hw_async_write async_write;
regmap_hw_reg_write reg_write;
+ regmap_hw_reg_noinc_write reg_noinc_write;
regmap_hw_reg_update_bits reg_update_bits;
regmap_hw_read read;
regmap_hw_reg_read reg_read;
+ regmap_hw_reg_noinc_read reg_noinc_read;
regmap_hw_free_context free_context;
regmap_hw_async_alloc async_alloc;
u8 read_flag_mask;
--
2.36.1
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