1 files changed, 301 insertions, 0 deletions
diff --git a/drivers/mfd/ocelot-spi.c b/drivers/mfd/ocelot-spi.c
new file mode 100644
index 000000000..85021f94e
--- /dev/null
+++ b/drivers/mfd/ocelot-spi.c
@@ -0,0 +1,301 @@
+// 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_read = true,
+	.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 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ocelot_spi_ids);
+
+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);