[PATCH v2 2/4] regmap: Allow providing read/write callbacks through struct regmap_config

[Yadav, Pratyush]

Hi Simon,

On 07/05/20 07:36PM, Simon Glass wrote:
> >
> > If there a way to use DM w/o DT changes, we can definitely explore that...
> 
> You can certainly do that. Just device_bind() a driver that implements
> your access mechanism. So long as the driver uses the same access
> mechanism no matter what hardware it is running on, that makes sense.
> But from what you say above, that might not be true, so you would end
> up setting the platform data of the regmap driver from its parent.
> That's not terrible, but not ideal.
> 
> Given the simple access you need above, I think you could just add
> that as another option in the regmap, perhaps turning endianness into
> some flags?

I tried doing it without custom regmap accessors. The rough patch below 
is what I came up with. Does it look any better than custom accessors?

PS: I can probably play around with regmap ranges instead of using
'base_offset', but it gets the job done minimally so I think it is good 
enough for a proof-of-concept.
 
 -- 8< --
Subject: [RFC PATCH] regmap: allow specifying base offset and register shift and
 access size

To accommodate more complex access patterns that are needed in the
Cadence Sierra PHY driver (which will be added as a follow-up),
introduce 'base_offset' and 'reg_offset_shift', two values that can be
used to adjust the final regmap read/write address.

'base_offset' is an extra offset on the regmap base discovered from the
device tree. This is useful when some regmaps of a device need to access
memory at one offset, and some at another.

'reg_offset_shift' will shift the register offset left before access.

'size' can be used to specify the width of reads (1/2/4/8 bytes). If 0,
defaults to 4 bytes to maintain backward compatibility.

Signed-off-by: Pratyush Yadav <p.yadav at ti.com>
---
 drivers/core/regmap.c | 16 ++++++++++++----
 include/regmap.h      | 27 ++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/drivers/core/regmap.c b/drivers/core/regmap.c
index 41293e5af0..9bce719b45 100644
--- a/drivers/core/regmap.c
+++ b/drivers/core/regmap.c
@@ -38,6 +38,7 @@ static struct regmap *regmap_alloc(int count)
 	map = malloc(sizeof(*map) + sizeof(map->ranges[0]) * count);
 	if (!map)
 		return NULL;
+	memset(map, 0, sizeof(*map));
 	map->range_count = count;

 	return map;
@@ -258,6 +259,10 @@ struct regmap *devm_regmap_init(struct udevice *dev,
 	if (rc)
 		return ERR_PTR(rc);

+	(*mapp)->base_offset = config->base_offset;
+	(*mapp)->reg_offset_shift = config->reg_offset_shift;
+	(*mapp)->size = config->size;
+
 	devres_add(dev, mapp);
 	return *mapp;
 }
@@ -343,7 +348,9 @@ int regmap_raw_read_range(struct regmap *map, uint range_num, uint offset,
 	}
 	range = &map->ranges[range_num];

-	ptr = map_physmem(range->start + offset, val_len, MAP_NOCACHE);
+	offset <<= map->reg_offset_shift;
+
+	ptr = map_physmem(range->start + map->base_offset + offset, val_len, MAP_NOCACHE);

 	if (offset + val_len > range->size) {
 		debug("%s: offset/size combination invalid\n", __func__);
@@ -380,7 +387,7 @@ int regmap_raw_read(struct regmap *map, uint offset, void *valp, size_t val_len)

 int regmap_read(struct regmap *map, uint offset, uint *valp)
 {
-	return regmap_raw_read(map, offset, valp, REGMAP_SIZE_32);
+	return regmap_raw_read(map, offset, valp, map->size ? map->size : REGMAP_SIZE_32);
 }

 static inline void __write_8(u8 *addr, const u8 *val,
@@ -452,7 +459,8 @@ int regmap_raw_write_range(struct regmap *map, uint range_num, uint offset,
 	}
 	range = &map->ranges[range_num];

-	ptr = map_physmem(range->start + offset, val_len, MAP_NOCACHE);
+	offset <<= map->reg_offset_shift;
+	ptr = map_physmem(range->start + map->base_offset + offset, val_len, MAP_NOCACHE);

 	if (offset + val_len > range->size) {
 		debug("%s: offset/size combination invalid\n", __func__);
@@ -490,7 +498,7 @@ int regmap_raw_write(struct regmap *map, uint offset, const void *val,

 int regmap_write(struct regmap *map, uint offset, uint val)
 {
-	return regmap_raw_write(map, offset, &val, REGMAP_SIZE_32);
+	return regmap_raw_write(map, offset, &val, map->size ? map->size : REGMAP_SIZE_32);
 }

 int regmap_update_bits(struct regmap *map, uint offset, uint mask, uint val)
diff --git a/include/regmap.h b/include/regmap.h
index 2edbf9359a..4adb04f7e3 100644
--- a/include/regmap.h
+++ b/include/regmap.h
@@ -74,16 +74,41 @@ struct regmap_range {
 };

 struct regmap_bus;
-struct regmap_config;
+/**
+ * struct regmap_config - a way of accessing hardware/bus registers
+ *
+ * @base_offset: Offset from the base of the regmap for reads and writes.
+ *		 (OPTIONAL)
+ * @reg_offset_shift: Left shift register offset by this value before
+ *		      performing reads or writes. (OPTIONAL)
+ * @size: Size/width of the read or write operation. Defaults to
+ *	  REGMAP_SIZE_32 if set to zero.
+ */
+struct regmap_config {
+	u32 base_offset;
+	u32 reg_offset_shift;
+	enum regmap_size_t size;
+};

 /**
  * struct regmap - a way of accessing hardware/bus registers
  *
+ * @base_offset: Offset from the base of the regmap for reads and writes.
+ *		 (OPTIONAL)
+ * @reg_offset_shift: Left shift register offset by this value before
+ *		      performing reads or writes. (OPTIONAL)
+ * @size: Size/width of the read or write operation. Defaults to
+ *	  REGMAP_SIZE_32 if set to zero.
  * @range_count:	Number of ranges available within the map
  * @ranges:		Array of ranges
  */
 struct regmap {
 	enum regmap_endianness_t endianness;
+
+	u32 base_offset;
+	u32 reg_offset_shift;
+	enum regmap_size_t size;
+
 	int range_count;
 	struct regmap_range ranges[0];
 };

-- 
Regards,
Pratyush Yadav
Texas Instruments India