Date:   Wed, 22 Dec 2021 18:43:36 +0000
From:   linuxkernel@...utosys.co.uk
To:     linux-kernel@...r.kernel.org
Cc:     broonie@...nel.org
Subject: [RFC PATCH v2 1/5] Add Parity bit Calculation to regmaps

From: Christopher Tyerman <c.tyerman@...ebladeautomationsystems.co.uk>

regmap.h

Added bitmasks "parity_read_mask" and "parity_write_mask" for read
and write operations to regmap_config bit mask defines location of
the parity bit.

Added optional callback "parity_calc" to regmap_config to
calculate parity bit value

Added regmap_parity_calc_even() and regmap_parity_calc_odd()
functions to regmap_config for standard parity calculations.

internal.h

Added bitmasks "parity_read_mask" and "parity_write_mask" for read
and write operations to regmap bit mask defines location of
the parity bit.

Added optional callback "parity_calc" to regmap to
calculate parity bit value

Added regmap_parity_calc_even() and regmap_parity_calc_odd()
functions to regmap to for standard parity calculations.

regmap.c

Added parity8(), parity16(), parity32() and parity64() bitwise parity
bit calculation functions for different unsigned integer sizes.

Added parity_even() parity calculation for unsigned int that
uses appropriate parityX fixed size function

Added regmap_parity_calc_even() that calculate bool value of even
parity bit from read/write mask, reg and val using appropriate
combinations of parityX functions

Added regmap_parity_calc_odd() that just boolean complement of
regmap_parity_calc_even()

Altered *__regmap_init to copy parity_read_mask, parity_write_mask
and parity_calc to from config to map and assign default
regmap_parity_calc_even() to map->parity_calc if map->parity_calc()
undefined.

Added regmap_set_work_buf_parity_mask() that sets the parity bit in
provided workbuf to calculated parity value using assigned
map->parity_calc() using rwmask, reg and val for calculation
and mask for bit location

Altered _regmap_raw_write_impl() to calculate parity by adding call
to regmap_set_work_buf_parity_mask()

Altered _regmap_raw_read() to calculate parity by adding call
to regmap_set_work_buf_parity_mask()

	modified:   drivers/base/regmap/internal.h
	modified:   drivers/base/regmap/regmap.c
	modified:   include/linux/regmap.h

Signed-off-by: Christopher Tyerman <c.tyerman@...ebladeautomationsystems.co.uk>
---
 drivers/base/regmap/internal.h |   6 ++
 drivers/base/regmap/regmap.c   | 168 ++++++++++++++++++++++++++++++++-
 include/linux/regmap.h         |  32 +++++++
 3 files changed, 204 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index b1905916f7af..78df50694cf4 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -168,6 +168,12 @@ struct regmap {
 
 	/* if set, the regmap core can sleep */
 	bool can_sleep;
+
+	unsigned long parity_write_mask;
+	unsigned long parity_read_mask;
+
+	bool (*parity_calc)(unsigned long rwmask, unsigned int reg,
+						const void *val, size_t val_len);
 };
 
 struct regcache_ops {
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 2d74f9f82aa9..05c104659381 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -57,6 +57,13 @@ static int _regmap_bus_reg_write(void *context, unsigned int reg,
 static int _regmap_bus_raw_write(void *context, unsigned int reg,
 				 unsigned int val);
 
+static bool parity_even(uint v);
+
+static bool parity8_even(u8 v);
+static bool parity16_even(u16 v);
+static bool parity32_even(u32 v);
+static bool parity64_even(u64 v);
+
 bool regmap_reg_in_ranges(unsigned int reg,
 			  const struct regmap_range *ranges,
 			  unsigned int nranges)
@@ -892,6 +899,14 @@ struct regmap *__regmap_init(struct device *dev,
 		map->reg_update_bits = bus->reg_update_bits;
 	}
 
+	map->parity_write_mask = config->parity_write_mask;
+	map->parity_read_mask = config->parity_read_mask;
+
+	if (config->parity_calc)
+		map->parity_calc = config->parity_calc;
+	else
+		map->parity_calc = regmap_parity_calc_even;
+
 	reg_endian = regmap_get_reg_endian(bus, config);
 	val_endian = regmap_get_val_endian(dev, bus, config);
 
@@ -1655,6 +1670,31 @@ static void regmap_set_work_buf_flag_mask(struct regmap *map, int max_bytes,
 		buf[i] |= (mask >> (8 * i)) & 0xff;
 }
 
+static void regmap_set_work_buf_parity_mask(struct regmap *map, int max_bytes,
+					  unsigned long mask, unsigned long rwmask,
+					  unsigned int reg, const void *val, size_t val_len)
+{
+
+	bool paritybit;
+	u8 *buf;
+	int i;
+
+	if (!mask || !map->work_buf)
+		return;
+
+	paritybit = map->parity_calc(rwmask, reg, val, val_len);
+
+
+	if (paritybit) {
+		buf = map->work_buf;
+
+		for (i = 0; i < max_bytes; i++)
+			buf[i] |= (mask >> (8 * i)) & 0xff;
+	}
+}
+
+
+
 static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 				  const void *val, size_t val_len, bool noinc)
 {
@@ -1736,7 +1776,12 @@ static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 
 	map->format.format_reg(map->work_buf, reg, map->reg_shift);
 	regmap_set_work_buf_flag_mask(map, map->format.reg_bytes,
-				      map->write_flag_mask);
+								  map->write_flag_mask);
+
+
+	regmap_set_work_buf_parity_mask(map, map->format.reg_bytes,
+				map->parity_write_mask, map->write_flag_mask, reg, val, val_len);
+
 
 	/*
 	 * Essentially all I/O mechanisms will be faster with a single
@@ -1748,6 +1793,9 @@ static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 		val = work_val;
 	}
 
+
+
+
 	if (map->async && map->bus->async_write) {
 		struct regmap_async *async;
 
@@ -2674,7 +2722,12 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 
 	map->format.format_reg(map->work_buf, reg, map->reg_shift);
 	regmap_set_work_buf_flag_mask(map, map->format.reg_bytes,
-				      map->read_flag_mask);
+						map->read_flag_mask);
+
+	regmap_set_work_buf_parity_mask(map, map->format.reg_bytes,
+						map->parity_read_mask, map->read_flag_mask, reg,
+						val, val_len);
+
 	trace_regmap_hw_read_start(map, reg, val_len / map->format.val_bytes);
 
 	ret = map->bus->read(map->bus_context, map->work_buf,
@@ -3340,3 +3393,114 @@ static int __init regmap_initcall(void)
 	return 0;
 }
 postcore_initcall(regmap_initcall);
+
+
+/**
+ * regmap_parity_calc_even() - calculates Value of parity bit for even parity
+ *
+ * @rwmask: value of the read/write mask
+ * @reg: value of register
+ * @val: pointer to value of data
+ * @val_len: size of val
+ *
+ * Calculate the value of the parity bit for even parity
+ */
+bool regmap_parity_calc_even(unsigned long rwmask, unsigned int reg,
+							 const void *val, size_t val_len)
+{
+	bool paritybuf = 0;
+	uint count = 0;
+
+	while (count < val_len) {
+		if (val_len - count >= 8) {
+			paritybuf ^= parity64_even(*(u64 *)val+count);
+			count += 8;
+		} else if (val_len - count >= 4) {
+			paritybuf ^= parity32_even(*(u32 *)val+count);
+			count += 4;
+		} else if (val_len - count >= 2) {
+			paritybuf ^= parity16_even(*(u16 *)val+count);
+			count += 2;
+		} else if (val_len - count >= 1) {
+			paritybuf ^= parity8_even(*(u8 *)val+count);
+			count += 1;
+		}
+	}
+
+	return (parity_even(rwmask) ^ parity_even(reg) ^ paritybuf);
+}
+EXPORT_SYMBOL_GPL(regmap_parity_calc_even);
+
+/**
+ * regmap_parity_calc_odd() - calculates Value of parity bit for odd parity
+ *
+ * @rwmask: value of the read/write mask
+ * @reg: value of register
+ * @val: pointer to value of data
+ * @val_len: size of val
+ *
+ * Calculate the value of the parity bit for odd parity
+ */
+
+bool regmap_parity_calc_odd(unsigned long rwmask, unsigned int reg,
+							const void *val, size_t val_len)
+{
+	return !(regmap_parity_calc_even(rwmask, reg, val, val_len));
+
+
+}
+EXPORT_SYMBOL_GPL(regmap_parity_calc_odd);
+
+static bool parity_even(uint v)
+{
+	switch (sizeof(v)) {
+	case 1:
+		return parity8_even((u8)v);
+	case 2:
+		return parity16_even((u16)v);
+	case 4:
+		return parity32_even((u32)v);
+	case 8:
+	default:
+		return parity64_even((u64)v);
+
+	}
+}
+static bool parity8_even(u8 v)
+{
+	v ^= v >> 4;
+	v ^= v >> 2;
+	v ^= v >> 1;
+	return v & 1;
+}
+
+
+static bool parity16_even(u16 v)
+{
+	v ^= v >> 8;
+	v ^= v >> 4;
+	v ^= v >> 2;
+	v ^= v >> 1;
+	return v & 1;
+}
+
+static bool parity32_even(u32 v)
+{
+	v ^= v >> 16;
+	v ^= v >> 8;
+	v ^= v >> 4;
+	v ^= v >> 2;
+	v ^= v >> 1;
+	return v & 1;
+}
+
+static bool parity64_even(u64 v)
+{
+	v ^= v >> 32;
+	v ^= v >> 16;
+	v ^= v >> 8;
+	v ^= v >> 4;
+	v ^= v >> 2;
+	v ^= v >> 1;
+	return v & 1;
+}
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 22652e5fbc38..511fc9228e1d 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -354,6 +354,10 @@ typedef void (*regmap_unlock)(void *);
  * @hwlock_mode: The hardware spinlock mode, should be HWLOCK_IRQSTATE,
  *		 HWLOCK_IRQ or 0.
  * @can_sleep: Optional, specifies whether regmap operations can sleep.
+ *
+ * @parity_read_mask: bit mask of location of parity bit for reads
+ * @parity_write_mask: bit mask of location of parity bit for writes
+ * @parity_calc: Optional callback to calculate parity, defaults to even parity
  */
 struct regmap_config {
 	const char *name;
@@ -416,6 +420,12 @@ struct regmap_config {
 	unsigned int hwlock_mode;
 
 	bool can_sleep;
+
+	unsigned long parity_read_mask;
+	unsigned long parity_write_mask;
+	bool (*parity_calc)(unsigned long rwmask, unsigned int reg,
+						const void *val, size_t val_len);
+
 };
 
 /**
@@ -1237,6 +1247,11 @@ static inline int regmap_clear_bits(struct regmap *map,
 
 int regmap_test_bits(struct regmap *map, unsigned int reg, unsigned int bits);
 
+bool regmap_parity_calc_even(unsigned long rwmask, unsigned int reg,
+								const void *val, size_t val_len);
+bool regmap_parity_calc_odd(unsigned long rwmask, unsigned int reg,
+								const void *val, size_t val_len);
+
 /**
  * struct reg_field - Description of an register field
  *
@@ -1866,6 +1881,23 @@ static inline struct device *regmap_get_device(struct regmap *map)
 	return NULL;
 }
 
+static inline bool regmap_parity_calc_even(unsigned long rwmask, unsigned int reg,
+						const void *val, size_t val_len)
+{
+	WARN_ONCE(1, "regmap API is disabled");
+	return NULL;
+}
+
+static inline bool regmap_parity_calc_odd(unsigned long rwmask, unsigned int reg,
+						const void *val, size_t val_len)
+{
+	WARN_ONCE(1, "regmap API is disabled");
+	return NULL;
+}
+
+
 #endif
 
+
+
 #endif
-- 
2.25.1

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