media: Add MIPI CCI register access helper functions

The CSI2 specification specifies a standard method to access camera sensor
registers called "Camera Control Interface (CCI)".

This uses either 8 or 16 bit (big-endian wire order) register addresses
and supports 8, 16, 24 or 32 bit (big-endian wire order) register widths.

Currently a lot of Linux camera sensor drivers all have their own custom
helpers for this, often copy and pasted from other drivers.

Add a set of generic helpers for this so that all sensor drivers can
switch to a single common implementation.

These helpers take an extra optional "int *err" function parameter,
this can be used to chain a bunch of register accesses together with
only a single error check at the end, rather than needing to error
check each individual register access. The first failing call will
set the contents of err to a non 0 value and all other calls will
then become no-ops.

Link: https://lore.kernel.org/linux-media/59aefa7f-7bf9-6736-6040-39551329cd0a@redhat.com/

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: Tommaso Merciai <tomm.merciai@gmail.com>
Reviewed-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

1 files changed, 166 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/v4l2-cci.c b/drivers/media/v4l2-core/v4l2-cci.c
new file mode 100644
index 000000000000..bc2dbec019b0
--- /dev/null
+++ b/drivers/media/v4l2-core/v4l2-cci.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MIPI Camera Control Interface (CCI) register access helpers.
+ *
+ * Copyright (C) 2023 Hans de Goede <hansg@kernel.org>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/dev_printk.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
+
+#include <media/v4l2-cci.h>
+
+int cci_read(struct regmap *map, u32 reg, u64 *val, int *err)
+{
+	unsigned int len;
+	u8 buf[8];
+	int ret;
+
+	if (err && *err)
+		return *err;
+
+	len = FIELD_GET(CCI_REG_WIDTH_MASK, reg);
+	reg = FIELD_GET(CCI_REG_ADDR_MASK, reg);
+
+	ret = regmap_bulk_read(map, reg, buf, len);
+	if (ret) {
+		dev_err(regmap_get_device(map), "Error reading reg 0x%4x: %d\n",
+			reg, ret);
+		goto out;
+	}
+
+	switch (len) {
+	case 1:
+		*val = buf[0];
+		break;
+	case 2:
+		*val = get_unaligned_be16(buf);
+		break;
+	case 3:
+		*val = get_unaligned_be24(buf);
+		break;
+	case 4:
+		*val = get_unaligned_be32(buf);
+		break;
+	case 8:
+		*val = get_unaligned_be64(buf);
+		break;
+	default:
+		dev_err(regmap_get_device(map), "Error invalid reg-width %u for reg 0x%04x\n",
+			len, reg);
+		ret = -EINVAL;
+		break;
+	}
+
+out:
+	if (ret && err)
+		*err = ret;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cci_read);
+
+int cci_write(struct regmap *map, u32 reg, u64 val, int *err)
+{
+	unsigned int len;
+	u8 buf[8];
+	int ret;
+
+	if (err && *err)
+		return *err;
+
+	len = FIELD_GET(CCI_REG_WIDTH_MASK, reg);
+	reg = FIELD_GET(CCI_REG_ADDR_MASK, reg);
+
+	switch (len) {
+	case 1:
+		buf[0] = val;
+		break;
+	case 2:
+		put_unaligned_be16(val, buf);
+		break;
+	case 3:
+		put_unaligned_be24(val, buf);
+		break;
+	case 4:
+		put_unaligned_be32(val, buf);
+		break;
+	case 8:
+		put_unaligned_be64(val, buf);
+		break;
+	default:
+		dev_err(regmap_get_device(map), "Error invalid reg-width %u for reg 0x%04x\n",
+			len, reg);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = regmap_bulk_write(map, reg, buf, len);
+	if (ret)
+		dev_err(regmap_get_device(map), "Error writing reg 0x%4x: %d\n",
+			reg, ret);
+
+out:
+	if (ret && err)
+		*err = ret;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cci_write);
+
+int cci_update_bits(struct regmap *map, u32 reg, u64 mask, u64 val, int *err)
+{
+	u64 readval;
+	int ret;
+
+	ret = cci_read(map, reg, &readval, err);
+	if (ret)
+		return ret;
+
+	val = (readval & ~mask) | (val & mask);
+
+	return cci_write(map, reg, val, err);
+}
+EXPORT_SYMBOL_GPL(cci_update_bits);
+
+int cci_multi_reg_write(struct regmap *map, const struct cci_reg_sequence *regs,
+			unsigned int num_regs, int *err)
+{
+	unsigned int i;
+	int ret;
+
+	for (i = 0; i < num_regs; i++) {
+		ret = cci_write(map, regs[i].reg, regs[i].val, err);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cci_multi_reg_write);
+
+#if IS_ENABLED(CONFIG_V4L2_CCI_I2C)
+struct regmap *devm_cci_regmap_init_i2c(struct i2c_client *client,
+					int reg_addr_bits)
+{
+	struct regmap_config config = {
+		.reg_bits = reg_addr_bits,
+		.val_bits = 8,
+		.reg_format_endian = REGMAP_ENDIAN_BIG,
+		.disable_locking = true,
+	};
+
+	return devm_regmap_init_i2c(client, &config);
+}
+EXPORT_SYMBOL_GPL(devm_cci_regmap_init_i2c);
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
+MODULE_DESCRIPTION("MIPI Camera Control Interface (CCI) support");