RE: [PATCH v3 4/4] fpga: dfl: add support for N3000 nios private feature

[Wu, Hao]

> Subject: [PATCH v3 4/4] fpga: dfl: add support for N3000 nios private feature
> 
> This patch adds support for the nios handshake private feature on Intel
> N3000 FPGA Card. This private feature provides a handshake interface to
> FPGA NIOS firmware, which receives retimer configuration command from
> host
> and executes via an internal SPI master. When nios finished the
> configuration, host takes over the ownership of the SPI master to control
> an Intel MAX10 BMC Chip on the SPI bus.

Maybe you can add some more description on what NIOS is here for people
to understand this better.

> 
> For NIOS firmware handshake part, this driver requests the retimer
> configuration for NIOS with parameters from module param, and adds some
> sysfs nodes for user to query NIOS state.
> 
> For SPI part, this driver adds a spi-altera platform device as well as
> the MAX10 BMC spi slave info. A spi-altera driver will be matched to
> handle following the SPI work.
> 
> Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
> Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> Signed-off-by: Russ Weight <russell.h.weight@xxxxxxxxx>
> Reviewed-by: Tom Rix <trix@xxxxxxxxxx>
> ---
> v3: Add the doc for this driver.
>     Minor fixes for comments from Tom.
> ---
>  .../ABI/testing/sysfs-bus-dfl-devices-n3000-nios   |  18 +
>  Documentation/fpga/dfl-n3000-nios.rst              |  39 ++
>  Documentation/fpga/index.rst                       |   1 +
>  drivers/fpga/Kconfig                               |  12 +
>  drivers/fpga/Makefile                              |   2 +
>  drivers/fpga/dfl-n3000-nios.c                      | 518 +++++++++++++++++++++
>  6 files changed, 590 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-dfl-devices-
> n3000-nios
>  create mode 100644 Documentation/fpga/dfl-n3000-nios.rst
>  create mode 100644 drivers/fpga/dfl-n3000-nios.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-dfl-devices-n3000-nios
> b/Documentation/ABI/testing/sysfs-bus-dfl-devices-n3000-nios
> new file mode 100644
> index 0000000..fcfcdbd
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-dfl-devices-n3000-nios
> @@ -0,0 +1,18 @@
> +What:		/sys/bus/dfl/devices/dfl-fme.X.X/fec_mode
> +Date:		July 2020
> +KernelVersion:	5.9

I don't think we can catch up the 5.9-rc1 at this moment, so 5.10 please.

> +Contact:	Xu Yilun <yilun.xu@xxxxxxxxx>
> +Description:	Read-only. It returns the FEC mode of the ethernet retimer
> +		configured by NIOS firmware. "rs" for RS FEC mode, "kr" for
> +		KR FEC mode, "no" FOR NO FEC mode. The FEC mode could
> be set
> +		by module parameters, but it could only be set once after the
> +		board powers up.
> +		Format: string
> +
> +What:		/sys/bus/dfl/devices/dfl-fme.X.X/nios_fw_version

I think you have already modified the device name to dfl-dev.X, right?

> +Date:		July 2020
> +KernelVersion:	5.9

Ditto.

> +Contact:	Xu Yilun <yilun.xu@xxxxxxxxx>
> +Description:	Read-only. It returns the NIOS firmware version in FPGA. Its
> +		format is "major.minor.patch".
> +		Format: %x.%x.%x
> diff --git a/Documentation/fpga/dfl-n3000-nios.rst
> b/Documentation/fpga/dfl-n3000-nios.rst
> new file mode 100644
> index 0000000..391528e
> --- /dev/null
> +++ b/Documentation/fpga/dfl-n3000-nios.rst
> @@ -0,0 +1,39 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=====================================
> +DFL N3000 Nios Private Feature Driver
> +=====================================
> +
> +The dfl n3000 nios driver supports for the nios handshake private feature
> on
> +Intel N3000 FPGA Card.
> +
> +This private feature provides a handshake interface to FPGA NIOS firmware,
> +which receives the ethernet retimer configuration command from host and
> +do the configuration via an internal SPI master. When nios finished the
> +configuration, host takes over the ownership of the SPI master to control an
> +Intel MAX10 BMC Chip on the SPI bus.

Maybe it's better to unify the naming - Nios

> +
> +So the driver does 2 major tasks on probe, requires NIOS firmware to
> configure
> +the ethernet retimer by operating the handshake interfaces, and then
> creates a
> +spi master platform device with the MAX10 device info in spi_board_info.
> +
> +Module Parameters
> +=================
> +
> +The dfl n3000 nios driver supports the following module parameters:
> +
> +* fec_mode: string
> +  Require the NIOS firmware to set the FEC mode of the ethernet retimer on
> +  the PAC N3000 FPGA card. The possible values could be:
> +
> +  - "rs": RS FEC mode (default)
> +  - "kr": KR FEC mode
> +  - "no": NO FEC mode
> +
> +  The configuration could only be set once after the board powers up, the
> +  firmware will not accept a second configuration afterward. So the fec
> mode
> +  will not be changed if the module is reloaded with a different param value.
> +
> +  The configured value of the fec mode could be queried from sysfs node:
> +
> +  /sys/bus/dfl/devices/dfl-fme.X.X/fec_mode
> diff --git a/Documentation/fpga/index.rst b/Documentation/fpga/index.rst
> index f80f956..5fd3c37 100644
> --- a/Documentation/fpga/index.rst
> +++ b/Documentation/fpga/index.rst
> @@ -8,6 +8,7 @@ fpga
>      :maxdepth: 1
> 
>      dfl
> +    dfl-n3000-nios
> 
>  .. only::  subproject and html
> 
> diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> index 7cd5a29..f820142 100644
> --- a/drivers/fpga/Kconfig
> +++ b/drivers/fpga/Kconfig
> @@ -191,6 +191,18 @@ config FPGA_DFL_AFU
>  	  to the FPGA infrastructure via a Port. There may be more than one
>  	  Port/AFU per DFL based FPGA device.
> 
> +config FPGA_DFL_N3000_NIOS
> +        tristate "FPGA DFL N3000 NIOS Driver"
> +        depends on FPGA_DFL
> +        select REGMAP
> +        help
> +	  This is the driver for the nios handshake private feature on Intel
> +	  N3000 FPGA Card. This private feature provides a handshake
> interface
> +	  to FPGA NIOS firmware, which receives retimer configuration
> command
> +	  from host and executes via an internal SPI master. When nios
> finished
> +	  the configuration, host takes over the ownership of the SPI master
> to
> +	  control an Intel MAX10 BMC Chip on the SPI bus.
> +
>  config FPGA_DFL_PCI
>  	tristate "FPGA DFL PCIe Device Driver"
>  	depends on PCI && FPGA_DFL
> diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> index d8e21df..27f20f2 100644
> --- a/drivers/fpga/Makefile
> +++ b/drivers/fpga/Makefile
> @@ -44,5 +44,7 @@ dfl-fme-objs += dfl-fme-perf.o
>  dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
>  dfl-afu-objs += dfl-afu-error.o
> 
> +obj-$(CONFIG_FPGA_DFL_N3000_NIOS)      += dfl-n3000-nios.o
> +
>  # Drivers for FPGAs which implement DFL
>  obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
> diff --git a/drivers/fpga/dfl-n3000-nios.c b/drivers/fpga/dfl-n3000-nios.c
> new file mode 100644
> index 0000000..041d759
> --- /dev/null
> +++ b/drivers/fpga/dfl-n3000-nios.c
> @@ -0,0 +1,518 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for DFL N3000 NIOS private feature

Maybe "DFL device driver for Nios private feature on Intel PAC N3000".
It must be described clearly to avoid confusing.

> + *
> + * Copyright (C) 2019-2020 Intel Corporation, Inc.
> + *
> + * Authors:
> + *   Wu Hao <hao.wu@xxxxxxxxx>
> + *   Xu Yilun <yilun.xu@xxxxxxxxx>
> + */
> +#include <linux/bitfield.h>
> +#include <linux/errno.h>
> +#include <linux/io.h>
> +#include <linux/io-64-nonatomic-lo-hi.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/stddef.h>
> +#include <linux/spi/altera.h>
> +#include <linux/spi/spi.h>
> +#include <linux/types.h>
> +
> +#include "dfl.h"
> +
> +/**
> + * DOC: fec_mode (string)
> + *
> + * Require the NIOS firmware to set the FEC mode of the ethernet retimer
> on
> + * PAC N3000 FPGA card.
> + *
> + * "rs": RS FEC mode (default)
> + *
> + * "kr": KR FEC mode
> + *
> + * "no": NO FEC mode
> + *
> + * The configuration could only be set once after the board powers up, the
> + * firmware will not accept a second configuration afterward. So the fec
> mode
> + * will not be changed if the module is reloaded with a different param
> value.
> + *
> + * The configured value of the fec_mode could be queried from sysfs node:
> + *
> + * /sys/bus/dfl/devices/dfl-fme.X.X/fec_mode

s/dfl-fme.X.X/dfl-dev.X/

> + */
> +static char *fec_mode = "rs";
> +module_param(fec_mode, charp, 0444);
> +MODULE_PARM_DESC(child, "FEC mode");

Why it's child here? This description string doesn't help at all I think. : (
You can put the description from code comments into this description.

> +
> +/* N3000 NIOS private feature registers */
> +#define NIOS_SPI_PARAM			0x8
> +#define PARAM_SHIFT_MODE_MSK		BIT_ULL(1)
> +#define PARAM_SHIFT_MODE_MSB		0
> +#define PARAM_SHIFT_MODE_LSB		1
> +#define PARAM_DATA_WIDTH		GENMASK_ULL(7, 2)
> +#define PARAM_NUM_CS			GENMASK_ULL(13, 8)
> +#define PARAM_CLK_POL			BIT_ULL(14)
> +#define PARAM_CLK_PHASE			BIT_ULL(15)
> +#define PARAM_PERIPHERAL_ID		GENMASK_ULL(47, 32)
> +
> +#define NIOS_SPI_CTRL			0x10
> +#define CTRL_WR_DATA			GENMASK_ULL(31, 0)
> +#define CTRL_ADDR			GENMASK_ULL(44, 32)
> +#define CTRL_CMD_MSK			GENMASK_ULL(63, 62)
> +#define CTRL_CMD_NOP			0
> +#define CTRL_CMD_RD			1
> +#define CTRL_CMD_WR			2
> +
> +#define NIOS_SPI_STAT			0x18
> +#define STAT_RD_DATA			GENMASK_ULL(31, 0)
> +#define STAT_RW_VAL			BIT_ULL(32)
> +
> +/* nios handshake registers, indirect access */

Ditto

> +#define NIOS_INIT			0x1000
> +#define NIOS_INIT_DONE			BIT(0)
> +#define NIOS_INIT_START			BIT(1)
> +/* Mode for PKVL A, link 0, the same below */
> +#define REQ_FEC_MODE_A0_MSK		GENMASK(9, 8)
> +#define REQ_FEC_MODE_A1_MSK		GENMASK(11, 10)
> +#define REQ_FEC_MODE_A2_MSK		GENMASK(13, 12)
> +#define REQ_FEC_MODE_A3_MSK		GENMASK(15, 14)
> +#define REQ_FEC_MODE_B0_MSK		GENMASK(17, 16)
> +#define REQ_FEC_MODE_B1_MSK		GENMASK(19, 18)
> +#define REQ_FEC_MODE_B2_MSK		GENMASK(21, 20)
> +#define REQ_FEC_MODE_B3_MSK		GENMASK(23, 22)
> +#define REQ_FEC_MODE_NO			0x0
> +#define REQ_FEC_MODE_KR			0x1
> +#define REQ_FEC_MODE_RS			0x2

What does REQ mean?

> +
> +#define NIOS_FW_VERSION			0x1004
> +#define NIOS_FW_VERSION_PATCH		GENMASK(23, 20)
> +#define NIOS_FW_VERSION_MINOR		GENMASK(27, 24)
> +#define NIOS_FW_VERSION_MAJOR		GENMASK(31, 28)
> +
> +#define PKVL_A_MODE_STS			0x1020
> +#define PKVL_B_MODE_STS			0x1024
> +#define PKVL_MODE_STS_GROUP_MSK		GENMASK(15, 8)
> +#define PKVL_MODE_STS_GROUP_OK		0x0
> +#define PKVL_MODE_STS_ID_MSK		GENMASK(7, 0)
> +
> +#define NS_REGBUS_WAIT_TIMEOUT	10000		/* loop count */
> +#define NIOS_INIT_TIMEOUT		10000000	/* usec */
> +#define NIOS_INIT_TIME_INTV		100000		/* usec */
> +
> +struct dfl_n3000_nios {
> +	void __iomem *base;
> +	struct regmap *regmap;
> +	struct device *dev;
> +	struct platform_device *altera_spi;
> +};
> +
> +static int n3000_nios_writel(struct dfl_n3000_nios *ns, unsigned int reg,
> +			     unsigned int val)
> +{
> +	int ret;
> +
> +	ret = regmap_write(ns->regmap, reg, val);
> +	if (ret)
> +		dev_err(ns->dev, "fail to write reg 0x%x val 0x%x: %d\n",
> +			reg, val, ret);

Maybe this log printing should be added in regmap implementation side?
Then every user can save some code.

> +
> +	return ret;
> +}
> +
> +static int n3000_nios_readl(struct dfl_n3000_nios *ns, unsigned int reg,
> +			    unsigned int *val)
> +{
> +	int ret;
> +
> +	ret = regmap_read(ns->regmap, reg, val);
> +	if (ret)
> +		dev_err(ns->dev, "fail to read reg 0x%x: %d\n", reg, ret);
> +
> +	return ret;
> +}
> +
> +static ssize_t nios_fw_version_show(struct device *dev,
> +				    struct device_attribute *attr, char *buf)
> +{
> +	struct dfl_n3000_nios *ns = dev_get_drvdata(dev);
> +	unsigned int val;
> +	int ret;
> +
> +	ret = n3000_nios_readl(ns, NIOS_FW_VERSION, &val);
> +	if (ret)
> +		return ret;
> +
> +	return sprintf(buf, "%x.%x.%x\n",
> +		       (u8)FIELD_GET(NIOS_FW_VERSION_MAJOR, val),
> +		       (u8)FIELD_GET(NIOS_FW_VERSION_MINOR, val),
> +		       (u8)FIELD_GET(NIOS_FW_VERSION_PATCH, val));
> +}
> +static DEVICE_ATTR_RO(nios_fw_version);
> +
> +static ssize_t fec_mode_show(struct device *dev,
> +			     struct device_attribute *attr, char *buf)
> +{
> +	struct dfl_n3000_nios *ns = dev_get_drvdata(dev);
> +	unsigned int val, mode;
> +	int ret;
> +
> +	ret = n3000_nios_readl(ns, NIOS_INIT, &val);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * FEC mode should always be the same for all links, as we set them
> +	 * in this way.
> +	 */
> +	mode = FIELD_GET(REQ_FEC_MODE_A0_MSK, val);
> +	if (mode != FIELD_GET(REQ_FEC_MODE_A1_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_A2_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_A3_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_B0_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_B1_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_B2_MSK, val) ||
> +	    mode != FIELD_GET(REQ_FEC_MODE_B3_MSK, val))
> +		return -EFAULT;
> +
> +	switch (mode) {
> +	case REQ_FEC_MODE_NO:
> +		return sprintf(buf, "no\n");
> +	case REQ_FEC_MODE_KR:
> +		return sprintf(buf, "kr\n");
> +	case REQ_FEC_MODE_RS:
> +		return sprintf(buf, "rs\n");
> +	}
> +
> +	return -EFAULT;
> +}
> +static DEVICE_ATTR_RO(fec_mode);
> +
> +static struct attribute *n3000_nios_attrs[] = {
> +	&dev_attr_nios_fw_version.attr,
> +	&dev_attr_fec_mode.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(n3000_nios);
> +
> +static bool init_error_detected(struct dfl_n3000_nios *ns)
> +{
> +	unsigned int val;
> +
> +	if (n3000_nios_readl(ns, PKVL_A_MODE_STS, &val))
> +		return true;
> +
> +	if (FIELD_GET(PKVL_MODE_STS_GROUP_MSK, val) ==
> PKVL_MODE_STS_GROUP_OK)
> +		return true;
> +
> +	if (n3000_nios_readl(ns, PKVL_B_MODE_STS, &val))
> +		return true;
> +
> +	if (FIELD_GET(PKVL_MODE_STS_GROUP_MSK, val) ==
> PKVL_MODE_STS_GROUP_OK)
> +		return true;
> +
> +	return false;
> +}
> +
> +static void dump_error_stat(struct dfl_n3000_nios *ns)
> +{
> +	unsigned int val;
> +
> +	if (n3000_nios_readl(ns, PKVL_A_MODE_STS, &val)) {
> +		dev_err(ns->dev, "Could not read register
> PKVL_A_MODE_STS\n");

Why similar error log here again?

> +		return;
> +	}
> +
> +	dev_info(ns->dev, "PKVL_A_MODE_STS %x\n", val);
> +
> +	if (n3000_nios_readl(ns, PKVL_B_MODE_STS, &val)) {
> +		dev_err(ns->dev, "Could not read register
> PKVL_B_MODE_STS\n");
> +		return;
> +	}
> +
> +	dev_info(ns->dev, "PKVL_B_MODE_STS %x\n", val);
> +}
> +
> +static int n3000_nios_init_done_check(struct dfl_n3000_nios *ns)
> +{
> +	struct device *dev = ns->dev;
> +	unsigned int val, mode;
> +	int ret;
> +
> +	/*
> +	 * this SPI is shared by NIOS core inside FPGA, NIOS will use this SPI
> +	 * master to do some one time initialization after power up, and then
> +	 * release the control to OS. driver needs to poll on INIT_DONE to
> +	 * see when driver could take the control.
> +	 *
> +	 * Please note that after 3.x.x version, INIT_START is introduced, so
> +	 * driver needs to trigger START firstly and then check INIT_DONE.
> +	 */
> +
> +	ret = n3000_nios_readl(ns, NIOS_FW_VERSION, &val);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * If NIOS version register is totally uninitialized(== 0x0), then the
> +	 * NIOS firmware is missing. So host could take control of SPI master
> +	 * safely, but initialization work for NIOS is not done. This is an
> +	 * issue of FPGA image. We didn't error out because we need SPI
> master
> +	 * to reprogram a new image.
> +	 */
> +	if (val == 0) {
> +		dev_warn(dev, "NIOS version reg = 0x%x, skip INIT_DONE
> check, but PKVL may be uninitialized\n",
> +			 val);
> +		return 0;
> +	}
> +
> +	if (FIELD_GET(NIOS_FW_VERSION_MAJOR, val) >= 3) {
> +		/* read NIOS_INIT to check if PKVL INIT done or not */
> +		ret = n3000_nios_readl(ns, NIOS_INIT, &val);
> +		if (ret)
> +			return ret;
> +
> +		/* check if PKVLs are initialized already */
> +		if (val & NIOS_INIT_DONE || val & NIOS_INIT_START)
> +			goto nios_init_done;
> +
> +		/* configure FEC mode per module param */
> +		val = NIOS_INIT_START;
> +
> +		/* FEC mode will be ignored by hardware in 10G mode */
> +		if (!strcmp(fec_mode, "no"))
> +			mode = REQ_FEC_MODE_NO;
> +		else if (!strcmp(fec_mode, "kr"))
> +			mode = REQ_FEC_MODE_KR;
> +		else if (!strcmp(fec_mode, "rs"))
> +			mode = REQ_FEC_MODE_RS;
> +		else
> +			return -EINVAL;
> +
> +		/* set the same FEC mode for all links */
> +		val |= FIELD_PREP(REQ_FEC_MODE_A0_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_A1_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_A2_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_A3_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_B0_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_B1_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_B2_MSK, mode) |
> +		       FIELD_PREP(REQ_FEC_MODE_B3_MSK, mode);
> +
> +		ret = n3000_nios_writel(ns, NIOS_INIT, val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +nios_init_done:
> +	/* polls on NIOS_INIT_DONE */
> +	ret = regmap_read_poll_timeout(ns->regmap, NIOS_INIT, val,
> +				       val & NIOS_INIT_DONE,
> +				       NIOS_INIT_TIME_INTV,
> +				       NIOS_INIT_TIMEOUT);
> +	if (ret) {
> +		dev_err(dev, "NIOS_INIT_DONE %s\n",
> +			(ret == -ETIMEDOUT) ? "timed out" : "check error");
> +		goto dump_sts;
> +	}
> +
> +	/*
> +	 * after INIT_DONE is detected, it still needs to check if any ERR
> +	 * detected.
> +	 * We won't error out here even if error detected. Nios will release
> +	 * spi controller when INIT_DONE is set, so driver could continue to
> +	 * initialize spi controller device.
> +	 */
> +	if (init_error_detected(ns)) {
> +		dev_warn(dev, "NIOS_INIT_DONE OK, but err found during
> init\n");
> +		goto dump_sts;
> +	}
> +	return 0;
> +
> +dump_sts:
> +	dump_error_stat(ns);
> +
> +	return ret;
> +}
> +
> +struct spi_board_info m10_n3000_info = {
> +	.modalias = "m10-n3000",
> +	.max_speed_hz = 12500000,
> +	.bus_num = 0,
> +	.chip_select = 0,
> +};
> +
> +static int create_altera_spi_controller(struct dfl_n3000_nios *ns)
> +{
> +	struct altera_spi_platform_data pdata = { 0 };
> +	struct platform_device_info pdevinfo = { 0 };
> +	void __iomem *base = ns->base;
> +	u64 v;
> +
> +	v = readq(base + NIOS_SPI_PARAM);
> +
> +	pdata.mode_bits = SPI_CS_HIGH;
> +	if (FIELD_GET(PARAM_CLK_POL, v))
> +		pdata.mode_bits |= SPI_CPOL;
> +	if (FIELD_GET(PARAM_CLK_PHASE, v))
> +		pdata.mode_bits |= SPI_CPHA;
> +
> +	pdata.num_chipselect = FIELD_GET(PARAM_NUM_CS, v);
> +	pdata.bits_per_word_mask =
> +		SPI_BPW_RANGE_MASK(1, FIELD_GET(PARAM_DATA_WIDTH,
> v));
> +
> +	pdata.num_devices = 1;
> +	pdata.devices = &m10_n3000_info;
> +
> +	dev_dbg(ns->dev, "%s cs %u bpm 0x%x mode 0x%x\n", __func__,
> +		pdata.num_chipselect, pdata.bits_per_word_mask,
> +		pdata.mode_bits);
> +
> +	pdevinfo.name = "subdev_spi_altera";
> +	pdevinfo.id = PLATFORM_DEVID_AUTO;
> +	pdevinfo.parent = ns->dev;
> +	pdevinfo.data = &pdata;
> +	pdevinfo.size_data = sizeof(pdata);
> +
> +	ns->altera_spi = platform_device_register_full(&pdevinfo);
> +	return PTR_ERR_OR_ZERO(ns->altera_spi);
> +}
> +
> +static void destroy_altera_spi_controller(struct dfl_n3000_nios *ns)
> +{
> +	platform_device_unregister(ns->altera_spi);
> +}
> +
> +/* ns is the abbreviation of nios_spi */
> +static int ns_bus_poll_stat_timeout(void __iomem *base, u64 *v)

Why adding "bus" here? I just see it's polling on register bits, right?
It's a little confusing on ns_bus.

> +{
> +	int loops = NS_REGBUS_WAIT_TIMEOUT;
> +
> +	/*
> +	 * We don't use the time based timeout here for performance.
> +	 *
> +	 * The image reprograming engine is on max10 bmc chip, which is the
> spi
> +	 * device connected to altera spi controller. So the regbus read/write
> +	 * is on the critical path of PAC N3000 image reprograming. And
> usually
> +	 * the state changes in few loops, the time based timeout checking
> will
> +	 * add too much overhead on it.
> +	 *
> +	 * Anyway, 10000 times loop is large enough.
> +	 */
> +	do {
> +		*v = readq(base + NIOS_SPI_STAT);
> +		if (*v & STAT_RW_VAL)
> +			break;
> +		cpu_relax();
> +	} while (--loops);
> +
> +	return loops ? 0 : -ETIMEDOUT;
> +}
> +
> +static int ns_bus_reg_write(void *context, unsigned int reg, unsigned int val)
> +{
> +	void __iomem *base = context;
> +	u64 v = 0;
> +
> +	v |= FIELD_PREP(CTRL_CMD_MSK, CTRL_CMD_WR);
> +	v |= FIELD_PREP(CTRL_ADDR, reg);
> +	v |= FIELD_PREP(CTRL_WR_DATA, val);
> +	writeq(v, base + NIOS_SPI_CTRL);
> +
> +	return ns_bus_poll_stat_timeout(base, &v);
> +}
> +
> +static int ns_bus_reg_read(void *context, unsigned int reg, unsigned int *val)
> +{
> +	void __iomem *base = context;
> +	u64 v = 0;
> +	int ret;
> +
> +	v |= FIELD_PREP(CTRL_CMD_MSK, CTRL_CMD_RD);
> +	v |= FIELD_PREP(CTRL_ADDR, reg);
> +	writeq(v, base + NIOS_SPI_CTRL);
> +
> +	ret = ns_bus_poll_stat_timeout(base, &v);
> +	if (!ret)
> +		*val = FIELD_GET(STAT_RD_DATA, v);
> +
> +	return ret;
> +}
> +
> +static const struct regmap_config ns_regbus_cfg = {
> +	.reg_bits = 32,
> +	.reg_stride = 4,
> +	.val_bits = 32,
> +	.fast_io = true,
> +
> +	.reg_write = ns_bus_reg_write,
> +	.reg_read = ns_bus_reg_read,
> +};
> +
> +static int dfl_n3000_nios_probe(struct dfl_device *dfl_dev)
> +{
> +	struct device *dev = &dfl_dev->dev;
> +	struct dfl_n3000_nios *ns;
> +	int ret;
> +
> +	ns = devm_kzalloc(dev, sizeof(*ns), GFP_KERNEL);
> +	if (!ns)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(&dfl_dev->dev, ns);
> +
> +	ns->dev = dev;
> +
> +	ns->base = devm_ioremap_resource(&dfl_dev->dev, &dfl_dev-
> >mmio_res);
> +	if (IS_ERR(ns->base)) {
> +		dev_err(dev, "get mem resource fail!\n");

devm_ioremap_resource should print some error message, will that be enough?

> +		return PTR_ERR(ns->base);
> +	}
> +
> +	ns->regmap = devm_regmap_init(dev, NULL, ns->base,
> &ns_regbus_cfg);
> +	if (IS_ERR(ns->regmap))
> +		return PTR_ERR(ns->regmap);
> +
> +	ret = n3000_nios_init_done_check(ns);
> +	if (ret)
> +		return ret;
> +
> +	ret = create_altera_spi_controller(ns);
> +	if (ret)
> +		dev_err(dev, "altera spi controller create failed: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static void dfl_n3000_nios_remove(struct dfl_device *dfl_dev)
> +{
> +	struct dfl_n3000_nios *ns = dev_get_drvdata(&dfl_dev->dev);
> +
> +	destroy_altera_spi_controller(ns);
> +}
> +
> +#define FME_FEATURE_ID_N3000_NIOS	0xd
> +
> +static const struct dfl_device_id dfl_n3000_nios_ids[] = {
> +	{ FME_ID, FME_FEATURE_ID_N3000_NIOS },
> +	{ }
> +};
> +
> +static struct dfl_driver dfl_n3000_nios_driver = {
> +	.drv	= {
> +		.name       = "dfl-n3000-nios",
> +		.dev_groups = n3000_nios_groups,
> +	},
> +	.id_table = dfl_n3000_nios_ids,
> +	.probe   = dfl_n3000_nios_probe,
> +	.remove  = dfl_n3000_nios_remove,
> +};
> +
> +module_dfl_driver(dfl_n3000_nios_driver);
> +
> +MODULE_DEVICE_TABLE(dfl, dfl_n3000_nios_ids);
> +MODULE_DESCRIPTION("DFL N3000 NIOS driver");
> +MODULE_AUTHOR("Intel Corporation");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4