[PATCH v2] spi: Add FSI-attached SPI controller driver

[PATCH v2] spi: Add FSI-attached SPI controller driver

[Eddie James]

There exists a set of SPI controllers on some POWER processors that may
be accessed through the FSI bus. Add a driver to traverse the FSI CFAM
engine that can access and drive the SPI controllers. This driver would
typically be used by a baseboard management controller (BMC).

The SPI controllers operate by means of programming a sequencing engine
which automatically manages the usual SPI protocol buses. The driver
programs each transfer into the sequencer as various operations
specifying the slave chip and shifting data in and out on the lines.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
Changes since v1:
 - Add comments
 - Switch to upper/lower_32_bits rather than manually shifting
 - Use min rather than manual conditional
 - Switch to dev_dbg for reset log
 - Add a timeout and abort for multiple resets for the transfer init procedure
 - Add MODULE_DEVICE_TABLE
 - Misc minor clean up items

 MAINTAINERS           |   6 +
 drivers/spi/Kconfig   |   7 +
 drivers/spi/Makefile  |   1 +
 drivers/spi/spi-fsi.c | 542 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 556 insertions(+)
 create mode 100644 drivers/spi/spi-fsi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d6d838c..fa7a371 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6862,6 +6862,12 @@ S:	Maintained
 F:	drivers/i2c/busses/i2c-fsi.c
 F:	Documentation/devicetree/bindings/i2c/i2c-fsi.txt
 
+FSI-ATTACHED SPI DRIVER
+M:	Eddie James <eajames@linux.ibm.com>
+L:	linux-spi@vger.kernel.org
+S:	Maintained
+F:	drivers/spi/spi-fsi.c
+
 FSNOTIFY: FILESYSTEM NOTIFICATION INFRASTRUCTURE
 M:	Jan Kara <jack@suse.cz>
 R:	Amir Goldstein <amir73il@gmail.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index d6ed0c3..c6fc9f1 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -264,6 +264,13 @@ config SPI_FALCON
 	  has only been tested with m25p80 type chips. The hardware has no
 	  support for other types of SPI peripherals.
 
+config SPI_FSI
+	tristate "FSI SPI driver"
+	depends on FSI
+	help
+	  This enables support for the driver for FSI bus attached SPI
+	  controllers.
+
 config SPI_FSL_LPSPI
 	tristate "Freescale i.MX LPSPI controller"
 	depends on ARCH_MXC || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 9b65ec5..d4ea24e 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -40,6 +40,7 @@ spi-dw-midpci-objs			:= spi-dw-pci.o spi-dw-mid.o
 obj-$(CONFIG_SPI_EFM32)			+= spi-efm32.o
 obj-$(CONFIG_SPI_EP93XX)		+= spi-ep93xx.o
 obj-$(CONFIG_SPI_FALCON)		+= spi-falcon.o
+obj-$(CONFIG_SPI_FSI)			+= spi-fsi.o
 obj-$(CONFIG_SPI_FSL_CPM)		+= spi-fsl-cpm.o
 obj-$(CONFIG_SPI_FSL_DSPI)		+= spi-fsl-dspi.o
 obj-$(CONFIG_SPI_FSL_LIB)		+= spi-fsl-lib.o
diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
new file mode 100644
index 0000000..6bd87e2
--- /dev/null
+++ b/drivers/spi/spi-fsi.c
@@ -0,0 +1,542 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright (C) IBM Corporation 2020
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/fsi.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+
+#define FSI_ENGID_SPI			0x23
+#define FSI_MBOX_ROOT_CTRL_8		0x2860
+
+#define FSI2SPI_DATA0			0x00
+#define FSI2SPI_DATA1			0x04
+#define FSI2SPI_CMD			0x08
+#define  FSI2SPI_CMD_WRITE		 BIT(31)
+#define FSI2SPI_RESET			0x18
+#define FSI2SPI_STATUS			0x1c
+#define  FSI2SPI_STATUS_ANY_ERROR	 BIT(31)
+#define FSI2SPI_IRQ			0x20
+
+#define SPI_FSI_BASE			0x70000
+#define SPI_FSI_INIT_TIMEOUT_MS		1000
+#define SPI_FSI_MAX_TRANSFER_SIZE	2048
+
+#define SPI_FSI_ERROR			0x0
+#define SPI_FSI_COUNTER_CFG		0x1
+#define  SPI_FSI_COUNTER_CFG_LOOPS(x)	 (((u64)(x) & 0xffULL) << 32)
+#define SPI_FSI_CFG1			0x2
+#define SPI_FSI_CLOCK_CFG		0x3
+#define  SPI_FSI_CLOCK_CFG_MM_ENABLE	 BIT_ULL(32)
+#define  SPI_FSI_CLOCK_CFG_ECC_DISABLE	 (BIT_ULL(35) | BIT_ULL(33))
+#define  SPI_FSI_CLOCK_CFG_RESET1	 (BIT_ULL(36) | BIT_ULL(38))
+#define  SPI_FSI_CLOCK_CFG_RESET2	 (BIT_ULL(37) | BIT_ULL(39))
+#define  SPI_FSI_CLOCK_CFG_MODE		 (BIT_ULL(41) | BIT_ULL(42))
+#define  SPI_FSI_CLOCK_CFG_SCK_RECV_DEL	 GENMASK_ULL(51, 44)
+#define   SPI_FSI_CLOCK_CFG_SCK_NO_DEL	  BIT_ULL(51)
+#define  SPI_FSI_CLOCK_CFG_SCK_DIV	 GENMASK_ULL(63, 52)
+#define SPI_FSI_MMAP			0x4
+#define SPI_FSI_DATA_TX			0x5
+#define SPI_FSI_DATA_RX			0x6
+#define SPI_FSI_SEQUENCE		0x7
+#define  SPI_FSI_SEQUENCE_STOP		 0x00
+#define  SPI_FSI_SEQUENCE_SEL_SLAVE(x)	 (0x10 | ((x) & 0xf))
+#define  SPI_FSI_SEQUENCE_SHIFT_OUT(x)	 (0x30 | ((x) & 0xf))
+#define  SPI_FSI_SEQUENCE_SHIFT_IN(x)	 (0x40 | ((x) & 0xf))
+#define  SPI_FSI_SEQUENCE_COPY_DATA_TX	 0xc0
+#define  SPI_FSI_SEQUENCE_BRANCH(x)	 (0xe0 | ((x) & 0xf))
+#define SPI_FSI_STATUS			0x8
+#define  SPI_FSI_STATUS_ERROR		 \
+	(GENMASK_ULL(31, 21) | GENMASK_ULL(15, 12))
+#define  SPI_FSI_STATUS_SEQ_STATE	 GENMASK_ULL(55, 48)
+#define   SPI_FSI_STATUS_SEQ_STATE_IDLE	  BIT_ULL(48)
+#define  SPI_FSI_STATUS_TDR_UNDERRUN	 BIT_ULL(57)
+#define  SPI_FSI_STATUS_TDR_OVERRUN	 BIT_ULL(58)
+#define  SPI_FSI_STATUS_TDR_FULL	 BIT_ULL(59)
+#define  SPI_FSI_STATUS_RDR_UNDERRUN	 BIT_ULL(61)
+#define  SPI_FSI_STATUS_RDR_OVERRUN	 BIT_ULL(62)
+#define  SPI_FSI_STATUS_RDR_FULL	 BIT_ULL(63)
+#define  SPI_FSI_STATUS_ANY_ERROR	 \
+	(SPI_FSI_STATUS_ERROR | SPI_FSI_STATUS_TDR_UNDERRUN | \
+	 SPI_FSI_STATUS_TDR_OVERRUN | SPI_FSI_STATUS_RDR_UNDERRUN | \
+	 SPI_FSI_STATUS_RDR_OVERRUN)
+#define SPI_FSI_PORT_CTRL		0x9
+
+struct fsi_spi {
+	struct device *dev;	/* SPI controller device */
+	struct fsi_device *fsi;	/* FSI2SPI CFAM engine device */
+	u32 base;
+};
+
+struct fsi_spi_sequence {
+	int bit;
+	u64 data;
+};
+
+static int fsi_spi_check_status(struct fsi_spi *ctx)
+{
+	int rc;
+	u32 sts;
+	__be32 sts_be;
+
+	rc = fsi_device_read(ctx->fsi, FSI2SPI_STATUS, &sts_be,
+			     sizeof(sts_be));
+	if (rc)
+		return rc;
+
+	sts = be32_to_cpu(sts_be);
+	if (sts & FSI2SPI_STATUS_ANY_ERROR) {
+		dev_err(ctx->dev, "Error with FSI2SPI interface: %08x.\n", sts);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int fsi_spi_read_reg(struct fsi_spi *ctx, u32 offset, u64 *value)
+{
+	int rc;
+	__be32 cmd_be;
+	__be32 data_be;
+
+	*value = 0ULL;
+
+	cmd_be = cpu_to_be32(offset + ctx->base);
+	rc = fsi_device_write(ctx->fsi, FSI2SPI_CMD, &cmd_be, sizeof(cmd_be));
+	if (rc)
+		return rc;
+
+	rc = fsi_spi_check_status(ctx);
+	if (rc)
+		return rc;
+
+	rc = fsi_device_read(ctx->fsi, FSI2SPI_DATA0, &data_be,
+			     sizeof(data_be));
+	if (rc)
+		return rc;
+
+	*value |= (u64)be32_to_cpu(data_be) << 32;
+
+	rc = fsi_device_read(ctx->fsi, FSI2SPI_DATA1, &data_be,
+			     sizeof(data_be));
+	if (rc)
+		return rc;
+
+	*value |= (u64)be32_to_cpu(data_be);
+	dev_dbg(ctx->dev, "Read %02x[%016llx].\n", offset, *value);
+
+	return 0;
+}
+
+static int fsi_spi_write_reg(struct fsi_spi *ctx, u32 offset, u64 value)
+{
+	int rc;
+	__be32 cmd_be;
+	__be32 data_be;
+
+	dev_dbg(ctx->dev, "Write %02x[%016llx].\n", offset, value);
+
+	data_be = cpu_to_be32(upper_32_bits(value));
+	rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA0, &data_be,
+			      sizeof(data_be));
+	if (rc)
+		return rc;
+
+	data_be = cpu_to_be32(lower_32_bits(value));
+	rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA1, &data_be,
+			      sizeof(data_be));
+	if (rc)
+		return rc;
+
+	cmd_be = cpu_to_be32((offset + ctx->base) | FSI2SPI_CMD_WRITE);
+	rc = fsi_device_write(ctx->fsi, FSI2SPI_CMD, &cmd_be, sizeof(cmd_be));
+	if (rc)
+		return rc;
+
+	return fsi_spi_check_status(ctx);
+}
+
+static int fsi_spi_data_in(u64 in, u8 *rx, int len)
+{
+	int i;
+	int num_bytes = min(len, 8);
+
+	for (i = 0; i < num_bytes; ++i)
+		rx[i] = (u8)(in >> (8 * ((num_bytes - 1) - i)));
+
+	return num_bytes;
+}
+
+static int fsi_spi_data_out(u64 *out, const u8 *tx, int len)
+{
+	int i;
+	int num_bytes = min(len, 8);
+
+	*out = 0ULL;
+
+	for (i = 0; i < num_bytes; ++i)
+		*out |= (u64)tx[i] << (8 * (8 - (i + 1)));
+
+	return num_bytes;
+}
+
+static int fsi_spi_reset(struct fsi_spi *ctx)
+{
+	int rc;
+
+	dev_dbg(ctx->dev, "Resetting SPI controller.\n");
+
+	rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
+			       SPI_FSI_CLOCK_CFG_RESET1);
+	if (rc)
+		return rc;
+
+	return fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
+				 SPI_FSI_CLOCK_CFG_RESET2);
+}
+
+static int fsi_spi_sequence_add(struct fsi_spi_sequence *seq, u8 val)
+{
+	seq->data |= (u64)val << seq->bit;
+	seq->bit -= 8;
+
+	return ((64 - seq->bit) / 8) - 2;
+}
+
+static void fsi_spi_sequence_init(struct fsi_spi_sequence *seq)
+{
+	seq->bit = 56;
+	seq->data = 0ULL;
+}
+
+static int fsi_spi_sequence_transfer(struct fsi_spi *ctx,
+				     struct fsi_spi_sequence *seq,
+				     struct spi_transfer *transfer)
+{
+	int loops;
+	int idx;
+	int rc;
+	u8 len = min(transfer->len, 8U);
+	u8 rem = transfer->len % len;
+
+	loops = transfer->len / len;
+
+	if (transfer->tx_buf) {
+		idx = fsi_spi_sequence_add(seq,
+					   SPI_FSI_SEQUENCE_SHIFT_OUT(len));
+		if (rem)
+			rem = SPI_FSI_SEQUENCE_SHIFT_OUT(rem);
+	} else if (transfer->rx_buf) {
+		idx = fsi_spi_sequence_add(seq,
+					   SPI_FSI_SEQUENCE_SHIFT_IN(len));
+		if (rem)
+			rem = SPI_FSI_SEQUENCE_SHIFT_IN(rem);
+	} else {
+		return -EINVAL;
+	}
+
+	if (loops > 1) {
+		fsi_spi_sequence_add(seq, SPI_FSI_SEQUENCE_BRANCH(idx));
+
+		if (rem)
+			fsi_spi_sequence_add(seq, rem);
+
+		rc = fsi_spi_write_reg(ctx, SPI_FSI_COUNTER_CFG,
+				       SPI_FSI_COUNTER_CFG_LOOPS(loops - 1));
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int fsi_spi_transfer_data(struct fsi_spi *ctx,
+				 struct spi_transfer *transfer)
+{
+	int rc = 0;
+	u64 status = 0ULL;
+
+	if (transfer->tx_buf) {
+		int nb;
+		int sent = 0;
+		u64 out = 0ULL;
+		const u8 *tx = transfer->tx_buf;
+
+		while (transfer->len > sent) {
+			nb = fsi_spi_data_out(&out, &tx[sent],
+					      (int)transfer->len - sent);
+
+			rc = fsi_spi_write_reg(ctx, SPI_FSI_DATA_TX, out);
+			if (rc)
+				return rc;
+
+			do {
+				rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS,
+						      &status);
+				if (rc)
+					return rc;
+
+				if (status & SPI_FSI_STATUS_ANY_ERROR) {
+					rc = fsi_spi_reset(ctx);
+					if (rc)
+						return rc;
+
+					return -EREMOTEIO;
+				}
+			} while (status & SPI_FSI_STATUS_TDR_FULL);
+
+			sent += nb;
+		}
+	} else if (transfer->rx_buf) {
+		int recv = 0;
+		u64 in = 0ULL;
+		u8 *rx = transfer->rx_buf;
+
+		while (transfer->len > recv) {
+			do {
+				rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS,
+						      &status);
+				if (rc)
+					return rc;
+
+				if (status & SPI_FSI_STATUS_ANY_ERROR) {
+					rc = fsi_spi_reset(ctx);
+					if (rc)
+						return rc;
+
+					return -EREMOTEIO;
+				}
+			} while (!(status & SPI_FSI_STATUS_RDR_FULL));
+
+			rc = fsi_spi_read_reg(ctx, SPI_FSI_DATA_RX, &in);
+			if (rc)
+				return rc;
+
+			recv += fsi_spi_data_in(in, &rx[recv],
+						(int)transfer->len - recv);
+		}
+	}
+
+	return 0;
+}
+
+static int fsi_spi_transfer_init(struct fsi_spi *ctx)
+{
+	int rc;
+	bool reset = false;
+	unsigned long end;
+	u64 seq_state;
+	u64 clock_cfg = 0ULL;
+	u64 status = 0ULL;
+	u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
+		SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
+		FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
+
+	end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
+	do {
+		if (time_after(jiffies, end))
+			return -ETIMEDOUT;
+
+		rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS, &status);
+		if (rc)
+			return rc;
+
+		if (status & (SPI_FSI_STATUS_ANY_ERROR |
+			      SPI_FSI_STATUS_TDR_FULL |
+			      SPI_FSI_STATUS_RDR_FULL)) {
+			if (reset)
+				return -EIO;
+
+			rc = fsi_spi_reset(ctx);
+			if (rc)
+				return rc;
+
+			reset = true;
+			continue;
+		}
+
+		seq_state = status & SPI_FSI_STATUS_SEQ_STATE;
+	} while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
+
+	rc = fsi_spi_read_reg(ctx, SPI_FSI_CLOCK_CFG, &clock_cfg);
+	if (rc)
+		return rc;
+
+	if ((clock_cfg & (SPI_FSI_CLOCK_CFG_MM_ENABLE |
+			  SPI_FSI_CLOCK_CFG_ECC_DISABLE |
+			  SPI_FSI_CLOCK_CFG_MODE |
+			  SPI_FSI_CLOCK_CFG_SCK_RECV_DEL |
+			  SPI_FSI_CLOCK_CFG_SCK_DIV)) != wanted_clock_cfg)
+		rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
+				       wanted_clock_cfg);
+
+	return rc;
+}
+
+static int fsi_spi_transfer_one_message(struct spi_controller *ctlr,
+					struct spi_message *mesg)
+{
+	int rc = 0;
+	u8 seq_slave = SPI_FSI_SEQUENCE_SEL_SLAVE(mesg->spi->chip_select + 1);
+	struct spi_transfer *transfer;
+	struct fsi_spi *ctx = spi_controller_get_devdata(ctlr);
+
+	list_for_each_entry(transfer, &mesg->transfers, transfer_list) {
+		struct fsi_spi_sequence seq;
+		struct spi_transfer *next = NULL;
+
+		/* Sequencer must do shift out (tx) first. */
+		if (!transfer->tx_buf ||
+		    transfer->len > SPI_FSI_MAX_TRANSFER_SIZE) {
+			rc = -EINVAL;
+			goto error;
+		}
+
+		dev_dbg(ctx->dev, "Start tx of %d bytes.\n", transfer->len);
+
+		rc = fsi_spi_transfer_init(ctx);
+		if (rc < 0)
+			goto error;
+
+		fsi_spi_sequence_init(&seq);
+		fsi_spi_sequence_add(&seq, seq_slave);
+
+		rc = fsi_spi_sequence_transfer(ctx, &seq, transfer);
+		if (rc)
+			goto error;
+
+		if (!list_is_last(&transfer->transfer_list,
+				  &mesg->transfers)) {
+			next = list_next_entry(transfer, transfer_list);
+
+			/* Sequencer can only do shift in (rx) after tx. */
+			if (next->rx_buf) {
+				if (next->len > SPI_FSI_MAX_TRANSFER_SIZE) {
+					rc = -EINVAL;
+					goto error;
+				}
+
+				dev_dbg(ctx->dev, "Sequence rx of %d bytes.\n",
+					next->len);
+
+				rc = fsi_spi_sequence_transfer(ctx, &seq,
+							       next);
+				if (rc)
+					goto error;
+			} else {
+				next = NULL;
+			}
+		}
+
+		fsi_spi_sequence_add(&seq, SPI_FSI_SEQUENCE_SEL_SLAVE(0));
+
+		rc = fsi_spi_write_reg(ctx, SPI_FSI_SEQUENCE, seq.data);
+		if (rc)
+			goto error;
+
+		rc = fsi_spi_transfer_data(ctx, transfer);
+		if (rc)
+			goto error;
+
+		if (next) {
+			rc = fsi_spi_transfer_data(ctx, next);
+			if (rc)
+				goto error;
+
+			transfer = next;
+		}
+	}
+
+error:
+	mesg->status = rc;
+	spi_finalize_current_message(ctlr);
+
+	return rc;
+}
+
+static size_t fsi_spi_max_transfer_size(struct spi_device *spi)
+{
+	return SPI_FSI_MAX_TRANSFER_SIZE;
+}
+
+static int fsi_spi_probe(struct device *dev)
+{
+	int rc;
+	u32 root_ctrl_8;
+	struct device_node *np;
+	int num_controllers_registered = 0;
+	struct fsi_device *fsi = to_fsi_dev(dev);
+
+	/*
+	 * Check the SPI mux before attempting to probe. If the mux isn't set
+	 * then the SPI controllers can't access their slave devices.
+	 */
+	rc = fsi_slave_read(fsi->slave, FSI_MBOX_ROOT_CTRL_8, &root_ctrl_8,
+			    sizeof(root_ctrl_8));
+	if (rc)
+		return rc;
+
+	if (!root_ctrl_8) {
+		dev_dbg(dev, "SPI mux not set, aborting probe.\n");
+		return -ENODEV;
+	}
+
+	for_each_available_child_of_node(dev->of_node, np) {
+		u32 base;
+		struct fsi_spi *ctx;
+		struct spi_controller *ctlr;
+
+		if (of_property_read_u32(np, "reg", &base))
+			continue;
+
+		ctlr = spi_alloc_master(dev, sizeof(*ctx));
+		if (!ctlr)
+			break;
+
+		ctlr->dev.of_node = np;
+		ctlr->num_chipselect = of_get_available_child_count(np) ?: 1;
+		ctlr->flags = SPI_CONTROLLER_HALF_DUPLEX;
+		ctlr->max_transfer_size = fsi_spi_max_transfer_size;
+		ctlr->transfer_one_message = fsi_spi_transfer_one_message;
+
+		ctx = spi_controller_get_devdata(ctlr);
+		ctx->dev = &ctlr->dev;
+		ctx->fsi = fsi;
+		ctx->base = base + SPI_FSI_BASE;
+
+		rc = devm_spi_register_controller(dev, ctlr);
+		if (rc)
+			spi_controller_put(ctlr);
+		else
+			num_controllers_registered++;
+	}
+
+	if (!num_controllers_registered)
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct fsi_device_id fsi_spi_ids[] = {
+	{ FSI_ENGID_SPI, FSI_VERSION_ANY },
+	{ }
+};
+MODULE_DEVICE_TABLE(fsi, fsi_spi_ids);
+
+static struct fsi_driver fsi_spi_driver = {
+	.id_table = fsi_spi_ids,
+	.drv = {
+		.name = "spi-fsi",
+		.bus = &fsi_bus_type,
+		.probe = fsi_spi_probe,
+	},
+};
+module_fsi_driver(fsi_spi_driver);
+
+MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
+MODULE_DESCRIPTION("FSI attached SPI controller");
+MODULE_LICENSE("GPL");
-- 
1.8.3.1

Re: [PATCH v2] spi: Add FSI-attached SPI controller driver

[Andy Shevchenko]

On Tue, Feb 4, 2020 at 12:30 AM Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> wrote:
>
> There exists a set of SPI controllers on some POWER processors that may
> be accessed through the FSI bus. Add a driver to traverse the FSI CFAM
> engine that can access and drive the SPI controllers. This driver would
> typically be used by a baseboard management controller (BMC).
>
> The SPI controllers operate by means of programming a sequencing engine
> which automatically manages the usual SPI protocol buses. The driver
> programs each transfer into the sequencer as various operations
> specifying the slave chip and shifting data in and out on the lines.

Some comments left unsettled in v1, thus applicable here.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] spi: Add FSI-attached SPI controller driver

[Eddie James]

On 2/4/20 5:05 AM, Andy Shevchenko wrote:
> On Tue, Feb 4, 2020 at 12:30 AM Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> wrote:
>> There exists a set of SPI controllers on some POWER processors that may
>> be accessed through the FSI bus. Add a driver to traverse the FSI CFAM
>> engine that can access and drive the SPI controllers. This driver would
>> typically be used by a baseboard management controller (BMC).
>>
>> The SPI controllers operate by means of programming a sequencing engine
>> which automatically manages the usual SPI protocol buses. The driver
>> programs each transfer into the sequencer as various operations
>> specifying the slave chip and shifting data in and out on the lines.
> Some comments left unsettled in v1, thus applicable here.


I think I addressed all of Andy's comments on v1 now, if Andy agreed 
about leaving the byte shifting as-is in fsi_spi_data_in/out.


Thanks,

Eddie


>

Re: [PATCH v2] spi: Add FSI-attached SPI controller driver

[Joel Stanley]

Hi Eddie,

Some comments below. For the most part it looks good.

On Mon, 3 Feb 2020 at 22:30, Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> wrote:

> +FSI-ATTACHED SPI DRIVER
> +M:     Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org>
> +L:     linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

Add linux-fsi-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org too

> +S:     Maintained
> +F:     drivers/spi/spi-fsi.c

> +static int fsi_spi_write_reg(struct fsi_spi *ctx, u32 offset, u64 value)
> +{
> +       int rc;
> +       __be32 cmd_be;
> +       __be32 data_be;
> +
> +       dev_dbg(ctx->dev, "Write %02x[%016llx].\n", offset, value);
> +
> +       data_be = cpu_to_be32(upper_32_bits(value));
> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA0, &data_be,
> +                             sizeof(data_be));
> +       if (rc)
> +               return rc;
> +
> +       data_be = cpu_to_be32(lower_32_bits(value));

The lower_32_bits cast is redundant (but harmless).

> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA1, &data_be,
> +                             sizeof(data_be));
> +       if (rc)
> +               return rc;
> +
> +       cmd_be = cpu_to_be32((offset + ctx->base) | FSI2SPI_CMD_WRITE);

offset + ctx->base must be less than 2 ^ 31 otherwise the top bit of
the address collides with the write command. Should we introduce a
check for that?

> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_CMD, &cmd_be, sizeof(cmd_be));
> +       if (rc)
> +               return rc;
> +
> +       return fsi_spi_check_status(ctx);
> +}
> +
> +static int fsi_spi_data_in(u64 in, u8 *rx, int len)
> +{
> +       int i;
> +       int num_bytes = min(len, 8);
> +
> +       for (i = 0; i < num_bytes; ++i)
> +               rx[i] = (u8)(in >> (8 * ((num_bytes - 1) - i)));
> +
> +       return num_bytes;
> +}
> +
> +static int fsi_spi_data_out(u64 *out, const u8 *tx, int len)
> +{
> +       int i;
> +       int num_bytes = min(len, 8);
> +
> +       *out = 0ULL;
> +
> +       for (i = 0; i < num_bytes; ++i)
> +               *out |= (u64)tx[i] << (8 * (8 - (i + 1)));

Did this work with non-8 byte transfers? I think the second 8 should
be num_bytes.

The loop requires careful reading to check. I wonder if we could do
this instead, which eliminates a lot duplicated loads and stores and
is easier to read:

       uint8_t *outp = (uint8_t *)out;

       for (i = 0; i < num_bytes; ++i) {
               outp[num_bytes - (i + 1)] = tx[i];
       }

> +
> +       return num_bytes;
> +}
> +
> +static int fsi_spi_reset(struct fsi_spi *ctx)
> +{
> +       int rc;
> +
> +       dev_dbg(ctx->dev, "Resetting SPI controller.\n");
> +
> +       rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> +                              SPI_FSI_CLOCK_CFG_RESET1);
> +       if (rc)
> +               return rc;
> +
> +       return fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> +                                SPI_FSI_CLOCK_CFG_RESET2);
> +}
> +
> +static int fsi_spi_sequence_add(struct fsi_spi_sequence *seq, u8 val)
> +{
> +       seq->data |= (u64)val << seq->bit;
> +       seq->bit -= 8;
> +
> +       return ((64 - seq->bit) / 8) - 2;

I have no idea what this is doing. Add a comment?

> +}

> +
> +static int fsi_spi_transfer_init(struct fsi_spi *ctx)
> +{
> +       int rc;
> +       bool reset = false;
> +       unsigned long end;
> +       u64 seq_state;
> +       u64 clock_cfg = 0ULL;
> +       u64 status = 0ULL;
> +       u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
> +               SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
> +               FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
> +
> +       end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
> +       do {
> +               if (time_after(jiffies, end))
> +                       return -ETIMEDOUT;

How tightly does this loop spin?

Should there be a delay inside of it?

> +
> +               rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS, &status);
> +               if (rc)
> +                       return rc;
> +
> +               if (status & (SPI_FSI_STATUS_ANY_ERROR |
> +                             SPI_FSI_STATUS_TDR_FULL |
> +                             SPI_FSI_STATUS_RDR_FULL)) {
> +                       if (reset)
> +                               return -EIO;
> +
> +                       rc = fsi_spi_reset(ctx);
> +                       if (rc)
> +                               return rc;
> +
> +                       reset = true;
> +                       continue;
> +               }
> +
> +               seq_state = status & SPI_FSI_STATUS_SEQ_STATE;
> +       } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));

../drivers/spi/spi-fsi.c: In function ‘fsi_spi_transfer_one_message’:
../drivers/spi/spi-fsi.c:363:11: warning: ‘seq_state’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
  363 |  } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
      |           ^~~~~~~~~


> +
> +       rc = fsi_spi_read_reg(ctx, SPI_FSI_CLOCK_CFG, &clock_cfg);
> +       if (rc)
> +               return rc;
> +
> +       if ((clock_cfg & (SPI_FSI_CLOCK_CFG_MM_ENABLE |
> +                         SPI_FSI_CLOCK_CFG_ECC_DISABLE |
> +                         SPI_FSI_CLOCK_CFG_MODE |
> +                         SPI_FSI_CLOCK_CFG_SCK_RECV_DEL |
> +                         SPI_FSI_CLOCK_CFG_SCK_DIV)) != wanted_clock_cfg)
> +               rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> +                                      wanted_clock_cfg);
> +
> +       return rc;
> +}

> +static int fsi_spi_probe(struct device *dev)
> +{
> +       int rc;
> +       u32 root_ctrl_8;
> +       struct device_node *np;
> +       int num_controllers_registered = 0;
> +       struct fsi_device *fsi = to_fsi_dev(dev);
> +
> +       /*
> +        * Check the SPI mux before attempting to probe. If the mux isn't set
> +        * then the SPI controllers can't access their slave devices.
> +        */
> +       rc = fsi_slave_read(fsi->slave, FSI_MBOX_ROOT_CTRL_8, &root_ctrl_8,
> +                           sizeof(root_ctrl_8));

Is it correct to stop probing if the mux is not set?

I assume it changes at runtime depending on the state of the host.
This could mean the driver probes correctly, but fails to work (if the
mux was set at BMC boot, but then changes).

Should it instead block reads/writes when the mux is in the incorrect state?

> +       if (rc)
> +               return rc;
> +
> +       if (!root_ctrl_8) {
> +               dev_dbg(dev, "SPI mux not set, aborting probe.\n");
> +               return -ENODEV;
> +       }
> +
> +       for_each_available_child_of_node(dev->of_node, np) {
> +               u32 base;
> +               struct fsi_spi *ctx;
> +               struct spi_controller *ctlr;
> +
> +               if (of_property_read_u32(np, "reg", &base))

It looks like this has a device tree binding. Can you add a document
describing it too?

> +                       continue;
> +
> +               ctlr = spi_alloc_master(dev, sizeof(*ctx));
> +               if (!ctlr)
> +                       break;
> +
> +               ctlr->dev.of_node = np;
> +               ctlr->num_chipselect = of_get_available_child_count(np) ?: 1;
> +               ctlr->flags = SPI_CONTROLLER_HALF_DUPLEX;
> +               ctlr->max_transfer_size = fsi_spi_max_transfer_size;
> +               ctlr->transfer_one_message = fsi_spi_transfer_one_message;
> +
> +               ctx = spi_controller_get_devdata(ctlr);
> +               ctx->dev = &ctlr->dev;
> +               ctx->fsi = fsi;
> +               ctx->base = base + SPI_FSI_BASE;
> +
> +               rc = devm_spi_register_controller(dev, ctlr);
> +               if (rc)
> +                       spi_controller_put(ctlr);
> +               else
> +                       num_controllers_registered++;
> +       }
> +
> +       if (!num_controllers_registered)
> +               return -ENODEV;
> +
> +       return 0;
> +}

Re: [PATCH v2] spi: Add FSI-attached SPI controller driver

[Andy Shevchenko]

On Tue, Feb 25, 2020 at 7:08 AM Joel Stanley <joel@jms.id.au> wrote:
> On Mon, 3 Feb 2020 at 22:30, Eddie James <eajames@linux.ibm.com> wrote:

...

> > +static int fsi_spi_data_in(u64 in, u8 *rx, int len)
> > +{
> > +       int i;
> > +       int num_bytes = min(len, 8);
> > +
> > +       for (i = 0; i < num_bytes; ++i)
> > +               rx[i] = (u8)(in >> (8 * ((num_bytes - 1) - i)));
> > +
> > +       return num_bytes;
> > +}
> > +
> > +static int fsi_spi_data_out(u64 *out, const u8 *tx, int len)
> > +{
> > +       int i;
> > +       int num_bytes = min(len, 8);
> > +
> > +       *out = 0ULL;
> > +
> > +       for (i = 0; i < num_bytes; ++i)
> > +               *out |= (u64)tx[i] << (8 * (8 - (i + 1)));
>
> Did this work with non-8 byte transfers? I think the second 8 should
> be num_bytes.
>
> The loop requires careful reading to check. I wonder if we could do
> this instead, which eliminates a lot duplicated loads and stores and
> is easier to read:
>
>        uint8_t *outp = (uint8_t *)out;
>
>        for (i = 0; i < num_bytes; ++i) {
>                outp[num_bytes - (i + 1)] = tx[i];
>        }

Have you had a chance to read my review of this? What do you think
about put_unaligned*()/get_unaligned*() instead of above?

> > +       return num_bytes;
> > +}

...

> > +static int fsi_spi_transfer_init(struct fsi_spi *ctx)
> > +{
> > +       int rc;
> > +       bool reset = false;
> > +       unsigned long end;
> > +       u64 seq_state;
> > +       u64 clock_cfg = 0ULL;
> > +       u64 status = 0ULL;
> > +       u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
> > +               SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
> > +               FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
> > +
> > +       end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
> > +       do {
> > +               if (time_after(jiffies, end))
> > +                       return -ETIMEDOUT;
>
> How tightly does this loop spin?
>
> Should there be a delay inside of it?
>
> > +
> > +               rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS, &status);
> > +               if (rc)
> > +                       return rc;
> > +
> > +               if (status & (SPI_FSI_STATUS_ANY_ERROR |
> > +                             SPI_FSI_STATUS_TDR_FULL |
> > +                             SPI_FSI_STATUS_RDR_FULL)) {
> > +                       if (reset)
> > +                               return -EIO;
> > +
> > +                       rc = fsi_spi_reset(ctx);
> > +                       if (rc)
> > +                               return rc;
> > +
> > +                       reset = true;
> > +                       continue;
> > +               }
> > +
> > +               seq_state = status & SPI_FSI_STATUS_SEQ_STATE;
> > +       } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
>
> ../drivers/spi/spi-fsi.c: In function ‘fsi_spi_transfer_one_message’:
> ../drivers/spi/spi-fsi.c:363:11: warning: ‘seq_state’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>   363 |  } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
>       |           ^~~~~~~~~

It's bogus warning, though, I think, easy to fix by reshuffling loop body.

> > +       rc = fsi_spi_read_reg(ctx, SPI_FSI_CLOCK_CFG, &clock_cfg);
> > +       if (rc)
> > +               return rc;
> > +
> > +       if ((clock_cfg & (SPI_FSI_CLOCK_CFG_MM_ENABLE |
> > +                         SPI_FSI_CLOCK_CFG_ECC_DISABLE |
> > +                         SPI_FSI_CLOCK_CFG_MODE |
> > +                         SPI_FSI_CLOCK_CFG_SCK_RECV_DEL |
> > +                         SPI_FSI_CLOCK_CFG_SCK_DIV)) != wanted_clock_cfg)
> > +               rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> > +                                      wanted_clock_cfg);
> > +
> > +       return rc;
> > +}

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] spi: Add FSI-attached SPI controller driver

[Eddie James]

On 2/24/20 11:08 PM, Joel Stanley wrote:
> Hi Eddie,
>
> Some comments below. For the most part it looks good.
>
> On Mon, 3 Feb 2020 at 22:30, Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> wrote:
>
>> +FSI-ATTACHED SPI DRIVER
>> +M:     Eddie James <eajames-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org>
>> +L:     linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Add linux-fsi-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org too
>
>> +S:     Maintained
>> +F:     drivers/spi/spi-fsi.c
>> +static int fsi_spi_write_reg(struct fsi_spi *ctx, u32 offset, u64 value)
>> +{
>> +       int rc;
>> +       __be32 cmd_be;
>> +       __be32 data_be;
>> +
>> +       dev_dbg(ctx->dev, "Write %02x[%016llx].\n", offset, value);
>> +
>> +       data_be = cpu_to_be32(upper_32_bits(value));
>> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA0, &data_be,
>> +                             sizeof(data_be));
>> +       if (rc)
>> +               return rc;
>> +
>> +       data_be = cpu_to_be32(lower_32_bits(value));
> The lower_32_bits cast is redundant (but harmless).
>
>> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_DATA1, &data_be,
>> +                             sizeof(data_be));
>> +       if (rc)
>> +               return rc;
>> +
>> +       cmd_be = cpu_to_be32((offset + ctx->base) | FSI2SPI_CMD_WRITE);
> offset + ctx->base must be less than 2 ^ 31 otherwise the top bit of
> the address collides with the write command. Should we introduce a
> check for that?


Sure, good idea.


>
>> +       rc = fsi_device_write(ctx->fsi, FSI2SPI_CMD, &cmd_be, sizeof(cmd_be));
>> +       if (rc)
>> +               return rc;
>> +
>> +       return fsi_spi_check_status(ctx);
>> +}
>> +
>> +static int fsi_spi_data_in(u64 in, u8 *rx, int len)
>> +{
>> +       int i;
>> +       int num_bytes = min(len, 8);
>> +
>> +       for (i = 0; i < num_bytes; ++i)
>> +               rx[i] = (u8)(in >> (8 * ((num_bytes - 1) - i)));
>> +
>> +       return num_bytes;
>> +}
>> +
>> +static int fsi_spi_data_out(u64 *out, const u8 *tx, int len)
>> +{
>> +       int i;
>> +       int num_bytes = min(len, 8);
>> +
>> +       *out = 0ULL;
>> +
>> +       for (i = 0; i < num_bytes; ++i)
>> +               *out |= (u64)tx[i] << (8 * (8 - (i + 1)));
> Did this work with non-8 byte transfers? I think the second 8 should
> be num_bytes.


No it should be 8. From the spec, "The value written to this register 
has to be left aligned." So to send 0x5a (1 byte) should write 
0x5a00000000000000. I've tested this with 1-7 byte writes and obtained 
the correct result.


>
> The loop requires careful reading to check. I wonder if we could do
> this instead, which eliminates a lot duplicated loads and stores and
> is easier to read:
>
>         uint8_t *outp = (uint8_t *)out;
>
>         for (i = 0; i < num_bytes; ++i) {
>                 outp[num_bytes - (i + 1)] = tx[i];
>         }


Yes that should also work (using 8 instead of num_bytes in the assignment).


>
>> +
>> +       return num_bytes;
>> +}
>> +
>> +static int fsi_spi_reset(struct fsi_spi *ctx)
>> +{
>> +       int rc;
>> +
>> +       dev_dbg(ctx->dev, "Resetting SPI controller.\n");
>> +
>> +       rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
>> +                              SPI_FSI_CLOCK_CFG_RESET1);
>> +       if (rc)
>> +               return rc;
>> +
>> +       return fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
>> +                                SPI_FSI_CLOCK_CFG_RESET2);
>> +}
>> +
>> +static int fsi_spi_sequence_add(struct fsi_spi_sequence *seq, u8 val)
>> +{
>> +       seq->data |= (u64)val << seq->bit;
>> +       seq->bit -= 8;
>> +
>> +       return ((64 - seq->bit) / 8) - 2;
> I have no idea what this is doing. Add a comment?


Sure. It's adding the next command to the sequence register and 
incrementing it's counter.


>
>> +}
>> +
>> +static int fsi_spi_transfer_init(struct fsi_spi *ctx)
>> +{
>> +       int rc;
>> +       bool reset = false;
>> +       unsigned long end;
>> +       u64 seq_state;
>> +       u64 clock_cfg = 0ULL;
>> +       u64 status = 0ULL;
>> +       u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
>> +               SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
>> +               FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
>> +
>> +       end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
>> +       do {
>> +               if (time_after(jiffies, end))
>> +                       return -ETIMEDOUT;
> How tightly does this loop spin?
>
> Should there be a delay inside of it?


Well, very tightly but I haven't seen it ever do more than a couple of 
iterations. And the timeout is 1 second. Not sure if we need a delay?


>
>> +
>> +               rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS, &status);
>> +               if (rc)
>> +                       return rc;
>> +
>> +               if (status & (SPI_FSI_STATUS_ANY_ERROR |
>> +                             SPI_FSI_STATUS_TDR_FULL |
>> +                             SPI_FSI_STATUS_RDR_FULL)) {
>> +                       if (reset)
>> +                               return -EIO;
>> +
>> +                       rc = fsi_spi_reset(ctx);
>> +                       if (rc)
>> +                               return rc;
>> +
>> +                       reset = true;
>> +                       continue;
>> +               }
>> +
>> +               seq_state = status & SPI_FSI_STATUS_SEQ_STATE;
>> +       } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
> ../drivers/spi/spi-fsi.c: In function ‘fsi_spi_transfer_one_message’:
> ../drivers/spi/spi-fsi.c:363:11: warning: ‘seq_state’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>    363 |  } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
>        |           ^~~~~~~~~
>

Strange that I don't see this when I compile. I'll move the seq_state 
assignment up.


>> +
>> +       rc = fsi_spi_read_reg(ctx, SPI_FSI_CLOCK_CFG, &clock_cfg);
>> +       if (rc)
>> +               return rc;
>> +
>> +       if ((clock_cfg & (SPI_FSI_CLOCK_CFG_MM_ENABLE |
>> +                         SPI_FSI_CLOCK_CFG_ECC_DISABLE |
>> +                         SPI_FSI_CLOCK_CFG_MODE |
>> +                         SPI_FSI_CLOCK_CFG_SCK_RECV_DEL |
>> +                         SPI_FSI_CLOCK_CFG_SCK_DIV)) != wanted_clock_cfg)
>> +               rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
>> +                                      wanted_clock_cfg);
>> +
>> +       return rc;
>> +}
>> +static int fsi_spi_probe(struct device *dev)
>> +{
>> +       int rc;
>> +       u32 root_ctrl_8;
>> +       struct device_node *np;
>> +       int num_controllers_registered = 0;
>> +       struct fsi_device *fsi = to_fsi_dev(dev);
>> +
>> +       /*
>> +        * Check the SPI mux before attempting to probe. If the mux isn't set
>> +        * then the SPI controllers can't access their slave devices.
>> +        */
>> +       rc = fsi_slave_read(fsi->slave, FSI_MBOX_ROOT_CTRL_8, &root_ctrl_8,
>> +                           sizeof(root_ctrl_8));
> Is it correct to stop probing if the mux is not set?
>
> I assume it changes at runtime depending on the state of the host.
> This could mean the driver probes correctly, but fails to work (if the
> mux was set at BMC boot, but then changes).


Right, it could change as the host switches the mux. I'm not sure what 
the correct option here is.


>
> Should it instead block reads/writes when the mux is in the incorrect state?


I see a couple of problems with this.

1) you'd have to check the state of the mux each time you try an operation?

2) how do slave devices (eeproms, etc) get probed up? They'd fail at 
first since operations are blocked, but then your master is probed with 
no easy way to probe the slave?


>
>> +       if (rc)
>> +               return rc;
>> +
>> +       if (!root_ctrl_8) {
>> +               dev_dbg(dev, "SPI mux not set, aborting probe.\n");
>> +               return -ENODEV;
>> +       }
>> +
>> +       for_each_available_child_of_node(dev->of_node, np) {
>> +               u32 base;
>> +               struct fsi_spi *ctx;
>> +               struct spi_controller *ctlr;
>> +
>> +               if (of_property_read_u32(np, "reg", &base))
> It looks like this has a device tree binding. Can you add a document
> describing it too?


Sure.


>
>> +                       continue;
>> +
>> +               ctlr = spi_alloc_master(dev, sizeof(*ctx));
>> +               if (!ctlr)
>> +                       break;
>> +
>> +               ctlr->dev.of_node = np;
>> +               ctlr->num_chipselect = of_get_available_child_count(np) ?: 1;
>> +               ctlr->flags = SPI_CONTROLLER_HALF_DUPLEX;
>> +               ctlr->max_transfer_size = fsi_spi_max_transfer_size;
>> +               ctlr->transfer_one_message = fsi_spi_transfer_one_message;
>> +
>> +               ctx = spi_controller_get_devdata(ctlr);
>> +               ctx->dev = &ctlr->dev;
>> +               ctx->fsi = fsi;
>> +               ctx->base = base + SPI_FSI_BASE;
>> +
>> +               rc = devm_spi_register_controller(dev, ctlr);
>> +               if (rc)
>> +                       spi_controller_put(ctlr);
>> +               else
>> +                       num_controllers_registered++;
>> +       }
>> +
>> +       if (!num_controllers_registered)
>> +               return -ENODEV;
>> +
>> +       return 0;
>> +}