mfd: ocelot: Add support for the vsc7512 chip via spi

The VSC7512 is a networking chip that contains several peripherals. Many of
these peripherals are currently supported by the VSC7513 and VSC7514 chips,
but those run on an internal CPU. The VSC7512 lacks this CPU, and must be
controlled externally.

Utilize the existing drivers by referencing the chip as an MFD. Add support
for the two MDIO buses, the internal phys, pinctrl, and serial GPIO.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220905162132.2943088-9-colin.foster@in-advantage.com

1 files changed, 299 insertions, 0 deletions

diff --git a/drivers/mfd/ocelot-spi.c b/drivers/mfd/ocelot-spi.c
new file mode 100644
index 000000000000..0f097f4829d1
--- /dev/null
+++ b/drivers/mfd/ocelot-spi.c
@@ -0,0 +1,299 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * SPI core driver for the Ocelot chip family.
+ *
+ * This driver will handle everything necessary to allow for communication over
+ * SPI to the VSC7511, VSC7512, VSC7513 and VSC7514 chips. The main functions
+ * are to prepare the chip's SPI interface for a specific bus speed, and a host
+ * processor's endianness. This will create and distribute regmaps for any
+ * children.
+ *
+ * Copyright 2021-2022 Innovative Advantage Inc.
+ *
+ * Author: Colin Foster <colin.foster@in-advantage.com>
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/ioport.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include "ocelot.h"
+
+#define REG_DEV_CPUORG_IF_CTRL		0x0000
+#define REG_DEV_CPUORG_IF_CFGSTAT	0x0004
+
+#define CFGSTAT_IF_NUM_VCORE		(0 << 24)
+#define CFGSTAT_IF_NUM_VRAP		(1 << 24)
+#define CFGSTAT_IF_NUM_SI		(2 << 24)
+#define CFGSTAT_IF_NUM_MIIM		(3 << 24)
+
+#define VSC7512_DEVCPU_ORG_RES_START	0x71000000
+#define VSC7512_DEVCPU_ORG_RES_SIZE	0x38
+
+#define VSC7512_CHIP_REGS_RES_START	0x71070000
+#define VSC7512_CHIP_REGS_RES_SIZE	0x14
+
+static const struct resource vsc7512_dev_cpuorg_resource =
+	DEFINE_RES_REG_NAMED(VSC7512_DEVCPU_ORG_RES_START,
+			     VSC7512_DEVCPU_ORG_RES_SIZE,
+			     "devcpu_org");
+
+static const struct resource vsc7512_gcb_resource =
+	DEFINE_RES_REG_NAMED(VSC7512_CHIP_REGS_RES_START,
+			     VSC7512_CHIP_REGS_RES_SIZE,
+			     "devcpu_gcb_chip_regs");
+
+static int ocelot_spi_initialize(struct device *dev)
+{
+	struct ocelot_ddata *ddata = dev_get_drvdata(dev);
+	u32 val, check;
+	int err;
+
+	val = OCELOT_SPI_BYTE_ORDER;
+
+	/*
+	 * The SPI address must be big-endian, but we want the payload to match
+	 * our CPU. These are two bits (0 and 1) but they're repeated such that
+	 * the write from any configuration will be valid. The four
+	 * configurations are:
+	 *
+	 * 0b00: little-endian, MSB first
+	 * |            111111   | 22221111 | 33222222 |
+	 * | 76543210 | 54321098 | 32109876 | 10987654 |
+	 *
+	 * 0b01: big-endian, MSB first
+	 * | 33222222 | 22221111 | 111111   |          |
+	 * | 10987654 | 32109876 | 54321098 | 76543210 |
+	 *
+	 * 0b10: little-endian, LSB first
+	 * |              111111 | 11112222 | 22222233 |
+	 * | 01234567 | 89012345 | 67890123 | 45678901 |
+	 *
+	 * 0b11: big-endian, LSB first
+	 * | 22222233 | 11112222 |   111111 |          |
+	 * | 45678901 | 67890123 | 89012345 | 01234567 |
+	 */
+	err = regmap_write(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CTRL, val);
+	if (err)
+		return err;
+
+	/*
+	 * Apply the number of padding bytes between a read request and the data
+	 * payload. Some registers have access times of up to 1us, so if the
+	 * first payload bit is shifted out too quickly, the read will fail.
+	 */
+	val = ddata->spi_padding_bytes;
+	err = regmap_write(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CFGSTAT, val);
+	if (err)
+		return err;
+
+	/*
+	 * After we write the interface configuration, read it back here. This
+	 * will verify several different things. The first is that the number of
+	 * padding bytes actually got written correctly. These are found in bits
+	 * 0:3.
+	 *
+	 * The second is that bit 16 is cleared. Bit 16 is IF_CFGSTAT:IF_STAT,
+	 * and will be set if the register access is too fast. This would be in
+	 * the condition that the number of padding bytes is insufficient for
+	 * the SPI bus frequency.
+	 *
+	 * The last check is for bits 31:24, which define the interface by which
+	 * the registers are being accessed. Since we're accessing them via the
+	 * serial interface, it must return IF_NUM_SI.
+	 */
+	check = val | CFGSTAT_IF_NUM_SI;
+
+	err = regmap_read(ddata->cpuorg_regmap, REG_DEV_CPUORG_IF_CFGSTAT, &val);
+	if (err)
+		return err;
+
+	if (check != val)
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct regmap_config ocelot_spi_regmap_config = {
+	.reg_bits = 24,
+	.reg_stride = 4,
+	.reg_downshift = 2,
+	.val_bits = 32,
+
+	.write_flag_mask = 0x80,
+
+	.use_single_write = true,
+	.can_multi_write = false,
+
+	.reg_format_endian = REGMAP_ENDIAN_BIG,
+	.val_format_endian = REGMAP_ENDIAN_NATIVE,
+};
+
+static int ocelot_spi_regmap_bus_read(void *context, const void *reg, size_t reg_size,
+				      void *val, size_t val_size)
+{
+	struct spi_transfer xfers[3] = {0};
+	struct device *dev = context;
+	struct ocelot_ddata *ddata;
+	struct spi_device *spi;
+	struct spi_message msg;
+	unsigned int index = 0;
+
+	ddata = dev_get_drvdata(dev);
+	spi = to_spi_device(dev);
+
+	xfers[index].tx_buf = reg;
+	xfers[index].len = reg_size;
+	index++;
+
+	if (ddata->spi_padding_bytes) {
+		xfers[index].len = ddata->spi_padding_bytes;
+		xfers[index].tx_buf = ddata->dummy_buf;
+		xfers[index].dummy_data = 1;
+		index++;
+	}
+
+	xfers[index].rx_buf = val;
+	xfers[index].len = val_size;
+	index++;
+
+	spi_message_init_with_transfers(&msg, xfers, index);
+
+	return spi_sync(spi, &msg);
+}
+
+static int ocelot_spi_regmap_bus_write(void *context, const void *data, size_t count)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	return spi_write(spi, data, count);
+}
+
+static const struct regmap_bus ocelot_spi_regmap_bus = {
+	.write = ocelot_spi_regmap_bus_write,
+	.read = ocelot_spi_regmap_bus_read,
+};
+
+struct regmap *ocelot_spi_init_regmap(struct device *dev, const struct resource *res)
+{
+	struct regmap_config regmap_config;
+
+	memcpy(&regmap_config, &ocelot_spi_regmap_config, sizeof(regmap_config));
+
+	regmap_config.name = res->name;
+	regmap_config.max_register = resource_size(res) - 1;
+	regmap_config.reg_base = res->start;
+
+	return devm_regmap_init(dev, &ocelot_spi_regmap_bus, dev, &regmap_config);
+}
+EXPORT_SYMBOL_NS(ocelot_spi_init_regmap, MFD_OCELOT_SPI);
+
+static int ocelot_spi_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct ocelot_ddata *ddata;
+	struct regmap *r;
+	int err;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	spi_set_drvdata(spi, ddata);
+
+	if (spi->max_speed_hz <= 500000) {
+		ddata->spi_padding_bytes = 0;
+	} else {
+		/*
+		 * Calculation taken from the manual for IF_CFGSTAT:IF_CFG.
+		 * Register access time is 1us, so we need to configure and send
+		 * out enough padding bytes between the read request and data
+		 * transmission that lasts at least 1 microsecond.
+		 */
+		ddata->spi_padding_bytes = 1 + (spi->max_speed_hz / HZ_PER_MHZ + 2) / 8;
+
+		ddata->dummy_buf = devm_kzalloc(dev, ddata->spi_padding_bytes, GFP_KERNEL);
+		if (!ddata->dummy_buf)
+			return -ENOMEM;
+	}
+
+	spi->bits_per_word = 8;
+
+	err = spi_setup(spi);
+	if (err)
+		return dev_err_probe(&spi->dev, err, "Error performing SPI setup\n");
+
+	r = ocelot_spi_init_regmap(dev, &vsc7512_dev_cpuorg_resource);
+	if (IS_ERR(r))
+		return PTR_ERR(r);
+
+	ddata->cpuorg_regmap = r;
+
+	r = ocelot_spi_init_regmap(dev, &vsc7512_gcb_resource);
+	if (IS_ERR(r))
+		return PTR_ERR(r);
+
+	ddata->gcb_regmap = r;
+
+	/*
+	 * The chip must be set up for SPI before it gets initialized and reset.
+	 * This must be done before calling init, and after a chip reset is
+	 * performed.
+	 */
+	err = ocelot_spi_initialize(dev);
+	if (err)
+		return dev_err_probe(dev, err, "Error initializing SPI bus\n");
+
+	err = ocelot_chip_reset(dev);
+	if (err)
+		return dev_err_probe(dev, err, "Error resetting device\n");
+
+	/*
+	 * A chip reset will clear the SPI configuration, so it needs to be done
+	 * again before we can access any registers.
+	 */
+	err = ocelot_spi_initialize(dev);
+	if (err)
+		return dev_err_probe(dev, err, "Error initializing SPI bus after reset\n");
+
+	err = ocelot_core_init(dev);
+	if (err)
+		return dev_err_probe(dev, err, "Error initializing Ocelot core\n");
+
+	return 0;
+}
+
+static const struct spi_device_id ocelot_spi_ids[] = {
+	{ "vsc7512", 0 },
+	{ }
+};
+
+static const struct of_device_id ocelot_spi_of_match[] = {
+	{ .compatible = "mscc,vsc7512" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ocelot_spi_of_match);
+
+static struct spi_driver ocelot_spi_driver = {
+	.driver = {
+		.name = "ocelot-soc",
+		.of_match_table = ocelot_spi_of_match,
+	},
+	.id_table = ocelot_spi_ids,
+	.probe = ocelot_spi_probe,
+};
+module_spi_driver(ocelot_spi_driver);
+
+MODULE_DESCRIPTION("SPI Controlled Ocelot Chip Driver");
+MODULE_AUTHOR("Colin Foster <colin.foster@in-advantage.com>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_IMPORT_NS(MFD_OCELOT);