Expand SoundWire MBQ register map support

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

The current SDCA MBQ (Multi-Byte Quantities) register map only
supports 16-bit types, add support for more sizes and then update
the rt722 driver to use the new support. We also add support for
the deferring feature of MBQs to allow hardware to indicate it is
not currently ready to service a read/write.

Afraid I don't have hardware to test the rt722 change so it is
only build tested, but I thought it good to include a change to
demonstrate the new features in use.

1 files changed, 197 insertions, 22 deletions

diff --git a/drivers/base/regmap/regmap-sdw-mbq.c b/drivers/base/regmap/regmap-sdw-mbq.c
index c99eada83780..86644bbd0710 100644
--- a/drivers/base/regmap/regmap-sdw-mbq.c
+++ b/drivers/base/regmap/regmap-sdw-mbq.c
@@ -1,45 +1,187 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright(c) 2020 Intel Corporation.
 
+#include <linux/bits.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/errno.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
 #include <linux/soundwire/sdw.h>
 #include <linux/soundwire/sdw_registers.h>
+#include <sound/sdca_function.h>
 #include "internal.h"
 
+struct regmap_mbq_context {
+	struct device *dev;
+
+	struct regmap_sdw_mbq_cfg cfg;
+
+	int val_size;
+	bool (*readable_reg)(struct device *dev, unsigned int reg);
+};
+
+static int regmap_sdw_mbq_size(struct regmap_mbq_context *ctx, unsigned int reg)
+{
+	int size = ctx->val_size;
+
+	if (ctx->cfg.mbq_size) {
+		size = ctx->cfg.mbq_size(ctx->dev, reg);
+		if (!size || size > ctx->val_size)
+			return -EINVAL;
+	}
+
+	return size;
+}
+
+static bool regmap_sdw_mbq_deferrable(struct regmap_mbq_context *ctx, unsigned int reg)
+{
+	if (ctx->cfg.deferrable)
+		return ctx->cfg.deferrable(ctx->dev, reg);
+
+	return false;
+}
+
+static int regmap_sdw_mbq_poll_busy(struct sdw_slave *slave, unsigned int reg,
+				    struct regmap_mbq_context *ctx)
+{
+	struct device *dev = &slave->dev;
+	int val, ret = 0;
+
+	dev_dbg(dev, "Deferring transaction for 0x%x\n", reg);
+
+	reg = SDW_SDCA_CTL(SDW_SDCA_CTL_FUNC(reg), 0,
+			   SDCA_CTL_ENTITY_0_FUNCTION_STATUS, 0);
+
+	if (ctx->readable_reg(dev, reg)) {
+		ret = read_poll_timeout(sdw_read_no_pm, val,
+					val < 0 || !(val & SDCA_CTL_ENTITY_0_FUNCTION_BUSY),
+					ctx->cfg.timeout_us, ctx->cfg.retry_us,
+					false, slave, reg);
+		if (val < 0)
+			return val;
+		if (ret)
+			dev_err(dev, "Function busy timed out 0x%x: %d\n", reg, val);
+	} else {
+		fsleep(ctx->cfg.timeout_us);
+	}
+
+	return ret;
+}
+
+static int regmap_sdw_mbq_write_impl(struct sdw_slave *slave,
+				     unsigned int reg, unsigned int val,
+				     int mbq_size, bool deferrable)
+{
+	int shift = mbq_size * BITS_PER_BYTE;
+	int ret;
+
+	while (--mbq_size > 0) {
+		shift -= BITS_PER_BYTE;
+
+		ret = sdw_write_no_pm(slave, SDW_SDCA_MBQ_CTL(reg),
+				      (val >> shift) & 0xff);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = sdw_write_no_pm(slave, reg, val & 0xff);
+	if (deferrable && ret == -ENODATA)
+		return -EAGAIN;
+
+	return ret;
+}
+
 static int regmap_sdw_mbq_write(void *context, unsigned int reg, unsigned int val)
 {
-	struct device *dev = context;
+	struct regmap_mbq_context *ctx = context;
+	struct device *dev = ctx->dev;
 	struct sdw_slave *slave = dev_to_sdw_dev(dev);
+	bool deferrable = regmap_sdw_mbq_deferrable(ctx, reg);
+	int mbq_size = regmap_sdw_mbq_size(ctx, reg);
 	int ret;
 
-	ret = sdw_write_no_pm(slave, SDW_SDCA_MBQ_CTL(reg), (val >> 8) & 0xff);
-	if (ret < 0)
-		return ret;
+	if (mbq_size < 0)
+		return mbq_size;
+
+	/*
+	 * Technically the spec does allow a device to set itself to busy for
+	 * internal reasons, but since it doesn't provide any information on
+	 * how to handle timeouts in that case, for now the code will only
+	 * process a single wait/timeout on function busy and a single retry
+	 * of the transaction.
+	 */
+	ret = regmap_sdw_mbq_write_impl(slave, reg, val, mbq_size, deferrable);
+	if (ret == -EAGAIN) {
+		ret = regmap_sdw_mbq_poll_busy(slave, reg, ctx);
+		if (ret)
+			return ret;
+
+		ret = regmap_sdw_mbq_write_impl(slave, reg, val, mbq_size, false);
+	}
+
+	return ret;
+}
+
+static int regmap_sdw_mbq_read_impl(struct sdw_slave *slave,
+				    unsigned int reg, unsigned int *val,
+				    int mbq_size, bool deferrable)
+{
+	int shift = BITS_PER_BYTE;
+	int read;
+
+	read = sdw_read_no_pm(slave, reg);
+	if (read < 0) {
+		if (deferrable && read == -ENODATA)
+			return -EAGAIN;
+
+		return read;
+	}
+
+	*val = read;
+
+	while (--mbq_size > 0) {
+		read = sdw_read_no_pm(slave, SDW_SDCA_MBQ_CTL(reg));
+		if (read < 0)
+			return read;
+
+		*val |= read << shift;
+		shift += BITS_PER_BYTE;
+	}
 
-	return sdw_write_no_pm(slave, reg, val & 0xff);
+	return 0;
 }
 
 static int regmap_sdw_mbq_read(void *context, unsigned int reg, unsigned int *val)
 {
-	struct device *dev = context;
+	struct regmap_mbq_context *ctx = context;
+	struct device *dev = ctx->dev;
 	struct sdw_slave *slave = dev_to_sdw_dev(dev);
-	int read0;
-	int read1;
+	bool deferrable = regmap_sdw_mbq_deferrable(ctx, reg);
+	int mbq_size = regmap_sdw_mbq_size(ctx, reg);
+	int ret;
 
-	read0 = sdw_read_no_pm(slave, reg);
-	if (read0 < 0)
-		return read0;
+	if (mbq_size < 0)
+		return mbq_size;
 
-	read1 = sdw_read_no_pm(slave, SDW_SDCA_MBQ_CTL(reg));
-	if (read1 < 0)
-		return read1;
+	/*
+	 * Technically the spec does allow a device to set itself to busy for
+	 * internal reasons, but since it doesn't provide any information on
+	 * how to handle timeouts in that case, for now the code will only
+	 * process a single wait/timeout on function busy and a single retry
+	 * of the transaction.
+	 */
+	ret = regmap_sdw_mbq_read_impl(slave, reg, val, mbq_size, deferrable);
+	if (ret == -EAGAIN) {
+		ret = regmap_sdw_mbq_poll_busy(slave, reg, ctx);
+		if (ret)
+			return ret;
 
-	*val = (read1 << 8) | read0;
+		ret = regmap_sdw_mbq_read_impl(slave, reg, val, mbq_size, false);
+	}
 
-	return 0;
+	return ret;
 }
 
 static const struct regmap_bus regmap_sdw_mbq = {
@@ -51,8 +193,7 @@ static const struct regmap_bus regmap_sdw_mbq = {
 
 static int regmap_sdw_mbq_config_check(const struct regmap_config *config)
 {
-	/* MBQ-based controls are only 16-bits for now */
-	if (config->val_bits != 16)
+	if (config->val_bits > (sizeof(unsigned int) * BITS_PER_BYTE))
 		return -ENOTSUPP;
 
 	/* Registers are 32 bits wide */
@@ -65,35 +206,69 @@ static int regmap_sdw_mbq_config_check(const struct regmap_config *config)
 	return 0;
 }
 
+static struct regmap_mbq_context *
+regmap_sdw_mbq_gen_context(struct device *dev,
+			   const struct regmap_config *config,
+			   const struct regmap_sdw_mbq_cfg *mbq_config)
+{
+	struct regmap_mbq_context *ctx;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	ctx->dev = dev;
+
+	if (mbq_config)
+		ctx->cfg = *mbq_config;
+
+	ctx->val_size = config->val_bits / BITS_PER_BYTE;
+	ctx->readable_reg = config->readable_reg;
+
+	return ctx;
+}
+
 struct regmap *__regmap_init_sdw_mbq(struct sdw_slave *sdw,
 				     const struct regmap_config *config,
+				     const struct regmap_sdw_mbq_cfg *mbq_config,
 				     struct lock_class_key *lock_key,
 				     const char *lock_name)
 {
+	struct regmap_mbq_context *ctx;
 	int ret;
 
 	ret = regmap_sdw_mbq_config_check(config);
 	if (ret)
 		return ERR_PTR(ret);
 
-	return __regmap_init(&sdw->dev, &regmap_sdw_mbq,
-			&sdw->dev, config, lock_key, lock_name);
+	ctx = regmap_sdw_mbq_gen_context(&sdw->dev, config, mbq_config);
+	if (IS_ERR(ctx))
+		return ERR_CAST(ctx);
+
+	return __regmap_init(&sdw->dev, &regmap_sdw_mbq, ctx,
+			     config, lock_key, lock_name);
 }
 EXPORT_SYMBOL_GPL(__regmap_init_sdw_mbq);
 
 struct regmap *__devm_regmap_init_sdw_mbq(struct sdw_slave *sdw,
 					  const struct regmap_config *config,
+					  const struct regmap_sdw_mbq_cfg *mbq_config,
 					  struct lock_class_key *lock_key,
 					  const char *lock_name)
 {
+	struct regmap_mbq_context *ctx;
 	int ret;
 
 	ret = regmap_sdw_mbq_config_check(config);
 	if (ret)
 		return ERR_PTR(ret);
 
-	return __devm_regmap_init(&sdw->dev, &regmap_sdw_mbq,
-			&sdw->dev, config, lock_key, lock_name);
+	ctx = regmap_sdw_mbq_gen_context(&sdw->dev, config, mbq_config);
+	if (IS_ERR(ctx))
+		return ERR_CAST(ctx);
+
+	return __devm_regmap_init(&sdw->dev, &regmap_sdw_mbq, ctx,
+				  config, lock_key, lock_name);
 }
 EXPORT_SYMBOL_GPL(__devm_regmap_init_sdw_mbq);