[PATCH 1/2] regmap: allow busses to request formatting with specific endianness

[PATCH 1/2] regmap: allow busses to request formatting with specific endianness

[Stephen Warren]

From: Stephen Warren <swarren@nvidia.com>

Add a field to struct regmap_bus that allows bus drivers to request that
register addresses and values be formatted with a specific endianness.

The default endianness is unchanged from current operation: Big.

Implement native endian formatting/parsing for 16- and 32-bit values.
This will be enough to support regmap-mmio.c.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
I'm not 100% sure if this is the approach you had in mind. However, anything
more all-encompassing would require separating the concepts of endianness and
serialization that are coupled together in functions like
regmap_format_4_12_write, and I'm not sure how that would work conceptually.

 drivers/base/regmap/regmap.c |   90 +++++++++++++++++++++++++++++++++++++-----
 include/linux/regmap.h       |    9 ++++
 2 files changed, 89 insertions(+), 10 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 2aa076e..33da8bd 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -119,13 +119,19 @@ static void regmap_format_8(void *buf, unsigned int val, unsigned int shift)
 	b[0] = val << shift;
 }
 
-static void regmap_format_16(void *buf, unsigned int val, unsigned int shift)
+static void regmap_format_16_be(void *buf, unsigned int val, unsigned int shift)
 {
 	__be16 *b = buf;
 
 	b[0] = cpu_to_be16(val << shift);
 }
 
+static void regmap_format_16_native(void *buf, unsigned int val,
+				    unsigned int shift)
+{
+	*(u16 *)buf = val << shift;
+}
+
 static void regmap_format_24(void *buf, unsigned int val, unsigned int shift)
 {
 	u8 *b = buf;
@@ -137,13 +143,19 @@ static void regmap_format_24(void *buf, unsigned int val, unsigned int shift)
 	b[2] = val;
 }
 
-static void regmap_format_32(void *buf, unsigned int val, unsigned int shift)
+static void regmap_format_32_be(void *buf, unsigned int val, unsigned int shift)
 {
 	__be32 *b = buf;
 
 	b[0] = cpu_to_be32(val << shift);
 }
 
+static void regmap_format_32_native(void *buf, unsigned int val,
+				    unsigned int shift)
+{
+	*(u32 *)buf = val << shift;
+}
+
 static unsigned int regmap_parse_8(void *buf)
 {
 	u8 *b = buf;
@@ -151,7 +163,7 @@ static unsigned int regmap_parse_8(void *buf)
 	return b[0];
 }
 
-static unsigned int regmap_parse_16(void *buf)
+static unsigned int regmap_parse_16_be(void *buf)
 {
 	__be16 *b = buf;
 
@@ -160,6 +172,11 @@ static unsigned int regmap_parse_16(void *buf)
 	return b[0];
 }
 
+static unsigned int regmap_parse_16_native(void *buf)
+{
+	return *(u16 *)buf;
+}
+
 static unsigned int regmap_parse_24(void *buf)
 {
 	u8 *b = buf;
@@ -170,7 +187,7 @@ static unsigned int regmap_parse_24(void *buf)
 	return ret;
 }
 
-static unsigned int regmap_parse_32(void *buf)
+static unsigned int regmap_parse_32_be(void *buf)
 {
 	__be32 *b = buf;
 
@@ -179,6 +196,11 @@ static unsigned int regmap_parse_32(void *buf)
 	return b[0];
 }
 
+static unsigned int regmap_parse_32_native(void *buf)
+{
+	return *(u32 *)buf;
+}
+
 static void regmap_lock_mutex(struct regmap *map)
 {
 	mutex_lock(&map->mutex);
@@ -279,6 +301,8 @@ struct regmap *regmap_init(struct device *dev,
 	case 2:
 		switch (config->val_bits) {
 		case 6:
+			if (bus->format_endian != REGMAP_ENDIAN_BIG)
+				goto err_map;
 			map->format.format_write = regmap_format_2_6_write;
 			break;
 		default:
@@ -289,6 +313,8 @@ struct regmap *regmap_init(struct device *dev,
 	case 4:
 		switch (config->val_bits) {
 		case 12:
+			if (bus->format_endian != REGMAP_ENDIAN_BIG)
+				goto err_map;
 			map->format.format_write = regmap_format_4_12_write;
 			break;
 		default:
@@ -299,6 +325,8 @@ struct regmap *regmap_init(struct device *dev,
 	case 7:
 		switch (config->val_bits) {
 		case 9:
+			if (bus->format_endian != REGMAP_ENDIAN_BIG)
+				goto err_map;
 			map->format.format_write = regmap_format_7_9_write;
 			break;
 		default:
@@ -309,6 +337,8 @@ struct regmap *regmap_init(struct device *dev,
 	case 10:
 		switch (config->val_bits) {
 		case 14:
+			if (bus->format_endian != REGMAP_ENDIAN_BIG)
+				goto err_map;
 			map->format.format_write = regmap_format_10_14_write;
 			break;
 		default:
@@ -321,11 +351,29 @@ struct regmap *regmap_init(struct device *dev,
 		break;
 
 	case 16:
-		map->format.format_reg = regmap_format_16;
+		switch (bus->format_endian) {
+		case REGMAP_ENDIAN_BIG:
+			map->format.format_reg = regmap_format_16_be;
+			break;
+		case REGMAP_ENDIAN_NATIVE:
+			map->format.format_reg = regmap_format_16_native;
+			break;
+		default:
+			goto err_map;
+		}
 		break;
 
 	case 32:
-		map->format.format_reg = regmap_format_32;
+		switch (bus->format_endian) {
+		case REGMAP_ENDIAN_BIG:
+			map->format.format_reg = regmap_format_32_be;
+			break;
+		case REGMAP_ENDIAN_NATIVE:
+			map->format.format_reg = regmap_format_32_native;
+			break;
+		default:
+			goto err_map;
+		}
 		break;
 
 	default:
@@ -338,16 +386,38 @@ struct regmap *regmap_init(struct device *dev,
 		map->format.parse_val = regmap_parse_8;
 		break;
 	case 16:
-		map->format.format_val = regmap_format_16;
-		map->format.parse_val = regmap_parse_16;
+		switch (bus->format_endian) {
+		case REGMAP_ENDIAN_BIG:
+			map->format.format_val = regmap_format_16_be;
+			map->format.parse_val = regmap_parse_16_be;
+			break;
+		case REGMAP_ENDIAN_NATIVE:
+			map->format.format_val = regmap_format_16_native;
+			map->format.parse_val = regmap_parse_16_native;
+			break;
+		default:
+			goto err_map;
+		}
 		break;
 	case 24:
+		if (bus->format_endian != REGMAP_ENDIAN_BIG)
+			goto err_map;
 		map->format.format_val = regmap_format_24;
 		map->format.parse_val = regmap_parse_24;
 		break;
 	case 32:
-		map->format.format_val = regmap_format_32;
-		map->format.parse_val = regmap_parse_32;
+		switch (bus->format_endian) {
+		case REGMAP_ENDIAN_BIG:
+			map->format.format_val = regmap_format_32_be;
+			map->format.parse_val = regmap_parse_32_be;
+			break;
+		case REGMAP_ENDIAN_NATIVE:
+			map->format.format_val = regmap_format_32_native;
+			map->format.parse_val = regmap_parse_32_native;
+			break;
+		default:
+			goto err_map;
+		}
 		break;
 	}
 
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 56af22e..6452afd 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -121,6 +121,12 @@ typedef int (*regmap_hw_read)(void *context,
 			      void *val_buf, size_t val_size);
 typedef void (*regmap_hw_free_context)(void *context);
 
+enum regmap_endian {
+	REGMAP_ENDIAN_BIG = 0, /* Compatible default if unspecified */
+	REGMAP_ENDIAN_LITTLE,
+	REGMAP_ENDIAN_NATIVE,
+};
+
 /**
  * Description of a hardware bus for the register map infrastructure.
  *
@@ -133,6 +139,8 @@ typedef void (*regmap_hw_free_context)(void *context);
  *         data.
  * @read_flag_mask: Mask to be set in the top byte of the register when doing
  *                  a read.
+ * @format_endian: Endianness for formatted register addresses, values, or
+ *                 serialized combinations thereof.
  */
 struct regmap_bus {
 	bool fast_io;
@@ -141,6 +149,7 @@ struct regmap_bus {
 	regmap_hw_read read;
 	regmap_hw_free_context free_context;
 	u8 read_flag_mask;
+	enum regmap_endian format_endian;
 };
 
 struct regmap *regmap_init(struct device *dev,
-- 
1.7.0.4

[PATCH 2/2] regmap: mmio: request native endian formatting

[Stephen Warren]

From: Stephen Warren <swarren@nvidia.com>

This will avoid the regmap core converting all addresses and values into
big endian, only for the mmio bus driver to have to convert them back to
native endian.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
 drivers/base/regmap/regmap-mmio.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index febd6de..49cdf59 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -37,7 +37,7 @@ static int regmap_mmio_gather_write(void *context,
 
 	BUG_ON(reg_size != 4);
 
-	offset = be32_to_cpup(reg);
+	offset = *(u32 *)reg;
 
 	while (val_size) {
 		switch (ctx->val_bytes) {
@@ -45,14 +45,14 @@ static int regmap_mmio_gather_write(void *context,
 			writeb(*(u8 *)val, ctx->regs + offset);
 			break;
 		case 2:
-			writew(be16_to_cpup(val), ctx->regs + offset);
+			writew(*(u16 *)val, ctx->regs + offset);
 			break;
 		case 4:
-			writel(be32_to_cpup(val), ctx->regs + offset);
+			writel(*(u32 *)val, ctx->regs + offset);
 			break;
 #ifdef CONFIG_64BIT
 		case 8:
-			writeq(be64_to_cpup(val), ctx->regs + offset);
+			writeq(*(u64 *)val, ctx->regs + offset);
 			break;
 #endif
 		default:
@@ -83,7 +83,7 @@ static int regmap_mmio_read(void *context,
 
 	BUG_ON(reg_size != 4);
 
-	offset = be32_to_cpup(reg);
+	offset = *(u32 *)reg;
 
 	while (val_size) {
 		switch (ctx->val_bytes) {
@@ -91,14 +91,14 @@ static int regmap_mmio_read(void *context,
 			*(u8 *)val = readb(ctx->regs + offset);
 			break;
 		case 2:
-			*(u16 *)val = cpu_to_be16(readw(ctx->regs + offset));
+			*(u16 *)val = readw(ctx->regs + offset);
 			break;
 		case 4:
-			*(u32 *)val = cpu_to_be32(readl(ctx->regs + offset));
+			*(u32 *)val = readl(ctx->regs + offset);
 			break;
 #ifdef CONFIG_64BIT
 		case 8:
-			*(u64 *)val = cpu_to_be32(readq(ctx->regs + offset));
+			*(u64 *)val = readq(ctx->regs + offset);
 			break;
 #endif
 		default:
@@ -124,6 +124,7 @@ static struct regmap_bus regmap_mmio = {
 	.gather_write = regmap_mmio_gather_write,
 	.read = regmap_mmio_read,
 	.free_context = regmap_mmio_free_context,
+	.format_endian = REGMAP_ENDIAN_NATIVE,
 };
 
 struct regmap_mmio_context *regmap_mmio_gen_context(void __iomem *regs,
-- 
1.7.0.4

Re: [PATCH 1/2] regmap: allow busses to request formatting with specific endianness

[Mark Brown]

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On Wed, May 23, 2012 at 04:33:53PM -0600, Stephen Warren wrote:

> I'm not 100% sure if this is the approach you had in mind. However, anything
> more all-encompassing would require separating the concepts of endianness and

I wouldn't do this on the bus in the first instance, I'd do it on the
device - it's pretty much orthogonal to the bus what the device wants
and it's perfectly plausible that a device on another bus might've made
unusual endiannness choices.  Otherwise it's pretty much what I was
thinking of.

For MMIO I'd expect that a large proportion of devices on platform buses
would pick native endianness.

> serialization that are coupled together in functions like
> regmap_format_4_12_write, and I'm not sure how that would work conceptually.

Anything using format_write() can be ignored, it's already lost large
chunks of functionality just from that.  Non-integer byte sizes cause
issues.

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Re: [PATCH 1/2] regmap: allow busses to request formatting with specific endianness

[Stephen Warren]

On 05/23/2012 05:16 PM, Mark Brown wrote:
> On Wed, May 23, 2012 at 04:33:53PM -0600, Stephen Warren wrote:
> 
>> I'm not 100% sure if this is the approach you had in mind.
>> However, anything more all-encompassing would require separating
>> the concepts of endianness and
> 
> I wouldn't do this on the bus in the first instance, I'd do it on
> the device - it's pretty much orthogonal to the bus what the device
> wants and it's perfectly plausible that a device on another bus
> might've made unusual endiannness choices.  Otherwise it's pretty
> much what I was thinking of.
> 
> For MMIO I'd expect that a large proportion of devices on platform
> buses would pick native endianness.

I did briefly consider making this a property of regmap_config rather
than regmap_bus, but as you say, it'd mean every MMIO user would have
to specify the endianness value.

Also, it doesn't seem right for a device to be able to specify
register formatting endianness for MMIO; presumably we'd always want
that native.

Perhaps the solution is to have two fields; one for address formatting
(the endianness of which regmap-mmio.c will error-check is "native",
like it error-checks other fields) and a second for value
formatting/parsing, which I can see a device might want to influence
(e.g. to fix a byte swap in HW).

I suppose we could avoid every device having to specify the endianness
by introducing a fourth "DEFAULT" value == 0, and having the bus
define what default means - that way, I wouldn't have to edit any
drivers due to adding the regmap_bus field.

>> serialization that are coupled together in functions like 
>> regmap_format_4_12_write, and I'm not sure how that would work
>> conceptually.
> 
> Anything using format_write() can be ignored, it's already lost
> large chunks of functionality just from that.  Non-integer byte
> sizes cause issues.

Re: [PATCH 1/2] regmap: allow busses to request formatting with specific endianness

[Mark Brown]

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On Wed, May 23, 2012 at 05:28:39PM -0600, Stephen Warren wrote:

> I did briefly consider making this a property of regmap_config rather
> than regmap_bus, but as you say, it'd mean every MMIO user would have
> to specify the endianness value.

I didn't say that, that'd be appauling!

> Also, it doesn't seem right for a device to be able to specify
> register formatting endianness for MMIO; presumably we'd always want
> that native.

Depends on what's going on with bought in IP and register map standards
(and things like PCI) - you do get non-native IPs turning up often enough.

> I suppose we could avoid every device having to specify the endianness
> by introducing a fourth "DEFAULT" value == 0, and having the bus
> define what default means - that way, I wouldn't have to edit any
> drivers due to adding the regmap_bus field.

That's absolutely essential, there's already an explicit idea of this in
the current code's assumption that everything is big endian.

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