Re: [PATCH v4 1/3] fpga: xilinx-spi: extract a common driver core

From: Xu Yilun
Date: Mon Feb 26 2024 - 04:54:50 EST

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On Wed, Feb 21, 2024 at 02:50:47PM -0500, Charles Perry wrote:
> Factor out the gpio handshaking (using PROGRAM_B, INIT_B and DONE)
> protocol in xilinx-core so that it can be reused for another driver.
> This commit does not change anything functionally to xilinx-spi.
>
> xilinx-core expects drivers to provide a single operation:
>
> * ->write(const char* buf, size_t count): write to the device
>
> As well as a struct device* for resource management.
>
> Signed-off-by: Charles Perry <charles.perry@xxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/fpga/Kconfig | 4 +
> drivers/fpga/Makefile | 1 +
> drivers/fpga/xilinx-core.c | 208 ++++++++++++++++++++++++++++++++++++
> drivers/fpga/xilinx-core.h | 28 +++++
> drivers/fpga/xilinx-spi.c | 212 +++----------------------------------
> 5 files changed, 254 insertions(+), 199 deletions(-)
> create mode 100644 drivers/fpga/xilinx-core.c
> create mode 100644 drivers/fpga/xilinx-core.h
>
> diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> index 2f689ac4ba3a3..d27a1ebf40838 100644
> --- a/drivers/fpga/Kconfig
> +++ b/drivers/fpga/Kconfig
> @@ -64,9 +64,13 @@ config FPGA_MGR_STRATIX10_SOC
> help
> FPGA manager driver support for the Intel Stratix10 SoC.
>
> +config FPGA_MGR_XILINX_CORE
> + tristate
> +
> config FPGA_MGR_XILINX_SPI
> tristate "Xilinx Configuration over Slave Serial (SPI)"
> depends on SPI
> + select FPGA_MGR_XILINX_CORE
> help
> FPGA manager driver support for Xilinx FPGA configuration
> over slave serial interface.
> diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> index 352a2612623e0..7ec795b6a5a70 100644
> --- a/drivers/fpga/Makefile
> +++ b/drivers/fpga/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_FPGA_MGR_SOCFPGA) += socfpga.o
> obj-$(CONFIG_FPGA_MGR_SOCFPGA_A10) += socfpga-a10.o
> obj-$(CONFIG_FPGA_MGR_STRATIX10_SOC) += stratix10-soc.o
> obj-$(CONFIG_FPGA_MGR_TS73XX) += ts73xx-fpga.o
> +obj-$(CONFIG_FPGA_MGR_XILINX_CORE) += xilinx-core.o
> obj-$(CONFIG_FPGA_MGR_XILINX_SPI) += xilinx-spi.o
> obj-$(CONFIG_FPGA_MGR_ZYNQ_FPGA) += zynq-fpga.o
> obj-$(CONFIG_FPGA_MGR_ZYNQMP_FPGA) += zynqmp-fpga.o
> diff --git a/drivers/fpga/xilinx-core.c b/drivers/fpga/xilinx-core.c
> new file mode 100644
> index 0000000000000..597e8b7a530b7
> --- /dev/null
> +++ b/drivers/fpga/xilinx-core.c
> @@ -0,0 +1,208 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Common parts of the Xilinx Spartan6 and 7 Series FPGA manager drivers.
> + *
> + * Copyright (C) 2017 DENX Software Engineering
> + *
> + * Anatolij Gustschin <agust@xxxxxxx>
> + */
> +
> +#include "xilinx-core.h"
> +
> +#include <linux/delay.h>
> +#include <linux/fpga/fpga-mgr.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/of.h>
> +
> +static int get_done_gpio(struct fpga_manager *mgr)
> +{
> + struct xilinx_fpga_core *core = mgr->priv;
> + int ret;
> +
> + ret = gpiod_get_value(core->done);
> + if (ret < 0)
> + dev_err(&mgr->dev, "Error reading DONE (%d)\n", ret);
> +
> + return ret;
> +}
> +
> +static enum fpga_mgr_states xilinx_core_state(struct fpga_manager *mgr)
> +{
> + if (!get_done_gpio(mgr))
> + return FPGA_MGR_STATE_RESET;
> +
> + return FPGA_MGR_STATE_UNKNOWN;
> +}
> +
> +/**
> + * wait_for_init_b - wait for the INIT_B pin to have a given state, or wait
> + * a given delay if the pin is unavailable
> + *
> + * @mgr: The FPGA manager object
> + * @value: Value INIT_B to wait for (1 = asserted = low)
> + * @alt_udelay: Delay to wait if the INIT_B GPIO is not available
> + *
> + * Returns 0 when the INIT_B GPIO reached the given state or -ETIMEDOUT if
> + * too much time passed waiting for that. If no INIT_B GPIO is available
> + * then always return 0.
> + */
> +static int wait_for_init_b(struct fpga_manager *mgr, int value,
> + unsigned long alt_udelay)
> +{
> + struct xilinx_fpga_core *core = mgr->priv;
> + unsigned long timeout = jiffies + msecs_to_jiffies(1000);
> +
> + if (core->init_b) {
> + while (time_before(jiffies, timeout)) {
> + int ret = gpiod_get_value(core->init_b);
> +
> + if (ret == value)
> + return 0;
> +
> + if (ret < 0) {
> + dev_err(&mgr->dev,
> + "Error reading INIT_B (%d)\n", ret);
> + return ret;
> + }
> +
> + usleep_range(100, 400);
> + }
> +
> + dev_err(&mgr->dev, "Timeout waiting for INIT_B to %s\n",
> + value ? "assert" : "deassert");
> + return -ETIMEDOUT;
> + }
> +
> + udelay(alt_udelay);
> +
> + return 0;
> +}
> +
> +static int xilinx_core_write_init(struct fpga_manager *mgr,
> + struct fpga_image_info *info, const char *buf,
> + size_t count)
> +{
> + struct xilinx_fpga_core *core = mgr->priv;
> + int err;
> +
> + if (info->flags & FPGA_MGR_PARTIAL_RECONFIG) {
> + dev_err(&mgr->dev, "Partial reconfiguration not supported\n");
> + return -EINVAL;
> + }
> +
> + gpiod_set_value(core->prog_b, 1);
> +
> + err = wait_for_init_b(mgr, 1, 1); /* min is 500 ns */
> + if (err) {
> + gpiod_set_value(core->prog_b, 0);
> + return err;
> + }
> +
> + gpiod_set_value(core->prog_b, 0);
> +
> + err = wait_for_init_b(mgr, 0, 0);
> + if (err)
> + return err;
> +
> + if (get_done_gpio(mgr)) {
> + dev_err(&mgr->dev, "Unexpected DONE pin state...\n");
> + return -EIO;
> + }
> +
> + /* program latency */
> + usleep_range(7500, 7600);
> + return 0;
> +}
> +
> +static int xilinx_core_write(struct fpga_manager *mgr, const char *buf,
> + size_t count)
> +{
> + struct xilinx_fpga_core *core = mgr->priv;
> +
> + return core->write(core, buf, count);
> +}
> +
> +static int xilinx_core_write_complete(struct fpga_manager *mgr,
> + struct fpga_image_info *info)
> +{
> + struct xilinx_fpga_core *core = mgr->priv;
> + unsigned long timeout =
> + jiffies + usecs_to_jiffies(info->config_complete_timeout_us);
> + bool expired = false;
> + int done;
> + int ret;
> + const char padding[1] = { 0xff };
> +
> + /*
> + * This loop is carefully written such that if the driver is
> + * scheduled out for more than 'timeout', we still check for DONE
> + * before giving up and we apply 8 extra CCLK cycles in all cases.
> + */
> + while (!expired) {
> + expired = time_after(jiffies, timeout);
> +
> + done = get_done_gpio(mgr);
> + if (done < 0)
> + return done;
> +
> + ret = core->write(core, padding, 1);
^

sizeof(padding), Use as less immediate numbers as possible.

> + if (ret)
> + return ret;
> +
> + if (done)
> + return 0;
> + }
> +
> + if (core->init_b) {
> + ret = gpiod_get_value(core->init_b);
> +
> + if (ret < 0) {
> + dev_err(&mgr->dev, "Error reading INIT_B (%d)\n", ret);
> + return ret;
> + }
> +
> + dev_err(&mgr->dev,
> + ret ? "CRC error or invalid device\n" :
> + "Missing sync word or incomplete bitstream\n");
> + } else {
> + dev_err(&mgr->dev, "Timeout after config data transfer\n");
> + }
> +
> + return -ETIMEDOUT;
> +}
> +
> +static const struct fpga_manager_ops xilinx_core_ops = {
> + .state = xilinx_core_state,
> + .write_init = xilinx_core_write_init,
> + .write = xilinx_core_write,
> + .write_complete = xilinx_core_write_complete,
> +};
> +
> +int xilinx_core_probe(struct xilinx_fpga_core *core)
> +{
> + struct fpga_manager *mgr;
> +
> + if (!core || !core->dev || !core->write)
> + return -EINVAL;
> +
> + /* PROGRAM_B is active low */
> + core->prog_b = devm_gpiod_get(core->dev, "prog_b", GPIOD_OUT_LOW);
> + if (IS_ERR(core->prog_b))
> + return dev_err_probe(core->dev, PTR_ERR(core->prog_b),
> + "Failed to get PROGRAM_B gpio\n");
> +
> + core->init_b = devm_gpiod_get_optional(core->dev, "init-b", GPIOD_IN);
> + if (IS_ERR(core->init_b))
> + return dev_err_probe(core->dev, PTR_ERR(core->init_b),
> + "Failed to get INIT_B gpio\n");
> +
> + core->done = devm_gpiod_get(core->dev, "done", GPIOD_IN);
> + if (IS_ERR(core->done))
> + return dev_err_probe(core->dev, PTR_ERR(core->done),
> + "Failed to get DONE gpio\n");
> +
> + mgr = devm_fpga_mgr_register(core->dev,
> + "Xilinx Slave Serial FPGA Manager",
> + &xilinx_core_ops, core);
> + return PTR_ERR_OR_ZERO(mgr);
> +}

EXPORT_SYMBOL_GPL() is needed? Have you ever built them as modules?
Try to follow Documentation/process/submit-checklist.rst as much as you can.

And MODULE_LICENSE() & MODULE_DESCRIPTION() please.

> diff --git a/drivers/fpga/xilinx-core.h b/drivers/fpga/xilinx-core.h
> new file mode 100644
> index 0000000000000..bea190287b403
> --- /dev/null
> +++ b/drivers/fpga/xilinx-core.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __XILINX_CORE_H
> +#define __XILINX_CORE_H
> +
> +#include <linux/device.h>
> +
> +/**
> + * struct xilinx_fpga_core - interface between the driver and the core manager
> + * of Xilinx 7 Series FPGA manager
> + * @dev: device node, must be set by the driver
> + * @write: write callback of the driver, must be set by the driver
> + * @prog_b: PROGRAM_B gpio, handled by the core manager
> + * @init_b: INIT_B gpio, handled by the core manager
> + * @done: DONE gpio, handled by the core manager

Internal fields are not listed in the generated output documentation.

> + */
> +struct xilinx_fpga_core {
> + struct device *dev;
> + int (*write)(struct xilinx_fpga_core *core, const char *buf,
> + size_t count);
> + struct gpio_desc *prog_b;
> + struct gpio_desc *init_b;
> + struct gpio_desc *done;

Use private tag here.

Please follow Documentation/doc-guide/kernel-doc.rst

> +};
> +
> +int xilinx_core_probe(struct xilinx_fpga_core *core);
> +
> +#endif /* __XILINX_CORE_H */
> diff --git a/drivers/fpga/xilinx-spi.c b/drivers/fpga/xilinx-spi.c
> index e1a227e7ff2ae..12f401502a53a 100644
> --- a/drivers/fpga/xilinx-spi.c
> +++ b/drivers/fpga/xilinx-spi.c
> @@ -10,127 +10,24 @@
> * the slave serial configuration interface.
> */
>
> -#include <linux/delay.h>
> -#include <linux/device.h>
> -#include <linux/fpga/fpga-mgr.h>
> -#include <linux/gpio/consumer.h>
> +#include "xilinx-core.h"
> +
> #include <linux/module.h>
> #include <linux/mod_devicetable.h>
> #include <linux/of.h>
> #include <linux/spi/spi.h>
> -#include <linux/sizes.h>
>
> struct xilinx_spi_conf {
> + struct xilinx_fpga_core core;
> struct spi_device *spi;
> - struct gpio_desc *prog_b;
> - struct gpio_desc *init_b;
> - struct gpio_desc *done;
> };
>
> -static int get_done_gpio(struct fpga_manager *mgr)
> -{
> - struct xilinx_spi_conf *conf = mgr->priv;
> - int ret;
> -
> - ret = gpiod_get_value(conf->done);
> -
> - if (ret < 0)
> - dev_err(&mgr->dev, "Error reading DONE (%d)\n", ret);
> -
> - return ret;
> -}
> -
> -static enum fpga_mgr_states xilinx_spi_state(struct fpga_manager *mgr)
> -{
> - if (!get_done_gpio(mgr))
> - return FPGA_MGR_STATE_RESET;
> -
> - return FPGA_MGR_STATE_UNKNOWN;
> -}
> -
> -/**
> - * wait_for_init_b - wait for the INIT_B pin to have a given state, or wait
> - * a given delay if the pin is unavailable
> - *
> - * @mgr: The FPGA manager object
> - * @value: Value INIT_B to wait for (1 = asserted = low)
> - * @alt_udelay: Delay to wait if the INIT_B GPIO is not available
> - *
> - * Returns 0 when the INIT_B GPIO reached the given state or -ETIMEDOUT if
> - * too much time passed waiting for that. If no INIT_B GPIO is available
> - * then always return 0.
> - */
> -static int wait_for_init_b(struct fpga_manager *mgr, int value,
> - unsigned long alt_udelay)
> -{
> - struct xilinx_spi_conf *conf = mgr->priv;
> - unsigned long timeout = jiffies + msecs_to_jiffies(1000);
> -
> - if (conf->init_b) {
> - while (time_before(jiffies, timeout)) {
> - int ret = gpiod_get_value(conf->init_b);
> -
> - if (ret == value)
> - return 0;
> -
> - if (ret < 0) {
> - dev_err(&mgr->dev, "Error reading INIT_B (%d)\n", ret);
> - return ret;
> - }
> -
> - usleep_range(100, 400);
> - }
> -
> - dev_err(&mgr->dev, "Timeout waiting for INIT_B to %s\n",
> - value ? "assert" : "deassert");
> - return -ETIMEDOUT;
> - }
> -
> - udelay(alt_udelay);
> -
> - return 0;
> -}
> -
> -static int xilinx_spi_write_init(struct fpga_manager *mgr,
> - struct fpga_image_info *info,
> - const char *buf, size_t count)
> -{
> - struct xilinx_spi_conf *conf = mgr->priv;
> - int err;
> -
> - if (info->flags & FPGA_MGR_PARTIAL_RECONFIG) {
> - dev_err(&mgr->dev, "Partial reconfiguration not supported\n");
> - return -EINVAL;
> - }
> -
> - gpiod_set_value(conf->prog_b, 1);
> -
> - err = wait_for_init_b(mgr, 1, 1); /* min is 500 ns */
> - if (err) {
> - gpiod_set_value(conf->prog_b, 0);
> - return err;
> - }
> -
> - gpiod_set_value(conf->prog_b, 0);
> +#define to_xilinx_spi_conf(obj) container_of(obj, struct xilinx_spi_conf, core)

Use to_spi_device(), then no need the MACRO or struct xilinx_spi_conf

Thanks,
Yilun

>
> - err = wait_for_init_b(mgr, 0, 0);
> - if (err)
> - return err;
> -
> - if (get_done_gpio(mgr)) {
> - dev_err(&mgr->dev, "Unexpected DONE pin state...\n");
> - return -EIO;
> - }
> -
> - /* program latency */
> - usleep_range(7500, 7600);
> - return 0;
> -}
> -
> -static int xilinx_spi_write(struct fpga_manager *mgr, const char *buf,
> +static int xilinx_spi_write(struct xilinx_fpga_core *core, const char *buf,
> size_t count)
> {
> - struct xilinx_spi_conf *conf = mgr->priv;
> + struct xilinx_spi_conf *conf = to_xilinx_spi_conf(core);
> const char *fw_data = buf;
> const char *fw_data_end = fw_data + count;
>
> @@ -143,7 +40,7 @@ static int xilinx_spi_write(struct fpga_manager *mgr, const char *buf,
>
> ret = spi_write(conf->spi, fw_data, stride);
> if (ret) {
> - dev_err(&mgr->dev, "SPI error in firmware write: %d\n",
> + dev_err(core->dev, "SPI error in firmware write: %d\n",
> ret);
> return ret;
> }
> @@ -153,109 +50,26 @@ static int xilinx_spi_write(struct fpga_manager *mgr, const char *buf,
> return 0;
> }
>
> -static int xilinx_spi_apply_cclk_cycles(struct xilinx_spi_conf *conf)
> -{
> - struct spi_device *spi = conf->spi;
> - const u8 din_data[1] = { 0xff };
> - int ret;
> -
> - ret = spi_write(conf->spi, din_data, sizeof(din_data));
> - if (ret)
> - dev_err(&spi->dev, "applying CCLK cycles failed: %d\n", ret);
> -
> - return ret;
> -}
> -
> -static int xilinx_spi_write_complete(struct fpga_manager *mgr,
> - struct fpga_image_info *info)
> -{
> - struct xilinx_spi_conf *conf = mgr->priv;
> - unsigned long timeout = jiffies + usecs_to_jiffies(info->config_complete_timeout_us);
> - bool expired = false;
> - int done;
> - int ret;
> -
> - /*
> - * This loop is carefully written such that if the driver is
> - * scheduled out for more than 'timeout', we still check for DONE
> - * before giving up and we apply 8 extra CCLK cycles in all cases.
> - */
> - while (!expired) {
> - expired = time_after(jiffies, timeout);
> -
> - done = get_done_gpio(mgr);
> - if (done < 0)
> - return done;
> -
> - ret = xilinx_spi_apply_cclk_cycles(conf);
> - if (ret)
> - return ret;
> -
> - if (done)
> - return 0;
> - }
> -
> - if (conf->init_b) {
> - ret = gpiod_get_value(conf->init_b);
> -
> - if (ret < 0) {
> - dev_err(&mgr->dev, "Error reading INIT_B (%d)\n", ret);
> - return ret;
> - }
> -
> - dev_err(&mgr->dev,
> - ret ? "CRC error or invalid device\n"
> - : "Missing sync word or incomplete bitstream\n");
> - } else {
> - dev_err(&mgr->dev, "Timeout after config data transfer\n");
> - }
> -
> - return -ETIMEDOUT;
> -}
> -
> -static const struct fpga_manager_ops xilinx_spi_ops = {
> - .state = xilinx_spi_state,
> - .write_init = xilinx_spi_write_init,
> - .write = xilinx_spi_write,
> - .write_complete = xilinx_spi_write_complete,
> -};
> -
> static int xilinx_spi_probe(struct spi_device *spi)
> {
> struct xilinx_spi_conf *conf;
> - struct fpga_manager *mgr;
>
> conf = devm_kzalloc(&spi->dev, sizeof(*conf), GFP_KERNEL);
> if (!conf)
> return -ENOMEM;
>
> + conf->core.dev = &spi->dev;
> + conf->core.write = xilinx_spi_write;
> conf->spi = spi;
>
> - /* PROGRAM_B is active low */
> - conf->prog_b = devm_gpiod_get(&spi->dev, "prog_b", GPIOD_OUT_LOW);
> - if (IS_ERR(conf->prog_b))
> - return dev_err_probe(&spi->dev, PTR_ERR(conf->prog_b),
> - "Failed to get PROGRAM_B gpio\n");
> -
> - conf->init_b = devm_gpiod_get_optional(&spi->dev, "init-b", GPIOD_IN);
> - if (IS_ERR(conf->init_b))
> - return dev_err_probe(&spi->dev, PTR_ERR(conf->init_b),
> - "Failed to get INIT_B gpio\n");
> -
> - conf->done = devm_gpiod_get(&spi->dev, "done", GPIOD_IN);
> - if (IS_ERR(conf->done))
> - return dev_err_probe(&spi->dev, PTR_ERR(conf->done),
> - "Failed to get DONE gpio\n");
> -
> - mgr = devm_fpga_mgr_register(&spi->dev,
> - "Xilinx Slave Serial FPGA Manager",
> - &xilinx_spi_ops, conf);
> - return PTR_ERR_OR_ZERO(mgr);
> + return xilinx_core_probe(&conf->core);
> }
>
> #ifdef CONFIG_OF
> static const struct of_device_id xlnx_spi_of_match[] = {
> - { .compatible = "xlnx,fpga-slave-serial", },
> + {
> + .compatible = "xlnx,fpga-slave-serial",
> + },
> {}
> };
> MODULE_DEVICE_TABLE(of, xlnx_spi_of_match);
> --
> 2.43.0
>
>

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