Date:   Sat, 5 Jan 2019 18:18:22 +0900
From:   Ben Whitten <ben.whitten@...il.com>
To:     Andreas Färber <afaerber@...e.de>,
        linux-lpwan@...ts.infradead.org, linux-serial@...r.kernel.org
Cc:     Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
        netdev@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH lora-next 3/5] net: lora: sx130x: Add PicoCell serdev
 driver

Hi,

On 04/01/2019 20:21, Andreas Färber wrote:
> The picoGW reference MCU firmware implements a USB CDC or UART interface
> with a set of serial commands. It can be found on multiple mPCIe cards
> as well as USB adapters.
> 
>    https://github.com/Lora-net/picoGW_mcu
> 
> That MCU design superseded earlier attempts of using FTDI chips (MPSSE)
> for controlling the SPI based chip directly from the host.
> 
> This commit adds a serdev driver implementing another regmap_bus to
> abstract the register access and reuses our existing regmap driver on top.
> Thereby we have an early proof of concept that we can drive both types
> of modules/cards with a single driver core!
> 
> It assumes there is only one SX130x (with its radios) accessible, whereas
> some new cards reportedly also have an SX127x on-board. So the DT/driver
> design may need to be reconsidered once such a card or documentation
> becomes available.
> It also assumes SX1255/1258 are fully compatible with "semtech,sx1257".
> 
> Currently there's still some bugs to be investigated, with communication
> stalling on one device and another reading the radio versions wrong
> (07 / 1f instead of 21, also observed on spi once).
> 
> Signed-off-by: Andreas Färber <afaerber@...e.de>
> ---
>   drivers/net/lora/Makefile        |   2 +
>   drivers/net/lora/sx130x_picogw.c | 466 +++++++++++++++++++++++++++++++++++++++

We are missing a Kconfig select or depend, compilation fails if 
CONFIG_SERIAL_DEV_BUS is not selected.

>   2 files changed, 468 insertions(+)
>   create mode 100644 drivers/net/lora/sx130x_picogw.c
> 
> diff --git a/drivers/net/lora/Makefile b/drivers/net/lora/Makefile
> index c6a0410f80ce..5fef38abf5ed 100644
> --- a/drivers/net/lora/Makefile
> +++ b/drivers/net/lora/Makefile
> @@ -25,6 +25,8 @@ lora-sx127x-y := sx127x.o
>   obj-$(CONFIG_LORA_SX130X) += lora-sx130x.o
>   lora-sx130x-y := sx130x.o
>   lora-sx130x-y += sx130x_radio.o
> +obj-$(CONFIG_LORA_SX130X) += lora-sx130x-picogw.o
> +lora-sx130x-picogw-y := sx130x_picogw.o
>   
>   obj-$(CONFIG_LORA_USI) += lora-usi.o
>   lora-usi-y := usi.o
> diff --git a/drivers/net/lora/sx130x_picogw.c b/drivers/net/lora/sx130x_picogw.c
> new file mode 100644
> index 000000000000..577f9fb71d46
> --- /dev/null
> +++ b/drivers/net/lora/sx130x_picogw.c
> @@ -0,0 +1,466 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Semtech SX1301/1308 PicoCell gateway serial MCU interface
> + *
> + * Copyright (c) 2018-2019 Andreas Färber
> + */
> +#include <linux/completion.h>
> +#include <linux/lora/sx130x.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/regmap.h>
> +#include <linux/serdev.h>
> +#include <linux/serial.h>
> +#include <linux/slab.h>
> +
> +struct picogw_device {
> +	struct serdev_device *serdev;
> +
> +	u8 rx_buf[1024];
> +	int rx_len;
> +
> +	struct completion answer_comp;
> +	struct completion answer_read_comp;
> +};
> +
> +static inline struct picogw_device *picogw_get_drvdata(struct serdev_device *sdev)
> +{
> +	return sx130x_get_drvdata(&sdev->dev);
> +}
> +
> +static bool picogw_valid_cmd(char ch)
> +{
> +	switch (ch) {
> +	case 'k': /* invalid command error */
> +	case 'r':
> +	case 'w':
> +	case 'l':
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static int picogw_send_cmd(struct picogw_device *picodev, char cmd,
> +	u8 addr, const void *data, u16 data_len)
> +{
> +	struct serdev_device *sdev = picodev->serdev;
> +	u8 buf[4];
> +	int i, ret;
> +
> +	buf[0] = cmd;
> +	buf[1] = (data_len >> 8) & 0xff;
> +	buf[2] = (data_len >> 0) & 0xff;
> +	buf[3] = addr;
> +
> +	dev_dbg(&sdev->dev, "%s: %c %02x %02x %02x\n", __func__, buf[0],
> +		(unsigned int)buf[1], (unsigned int)buf[2], (unsigned int)buf[3]);
> +	for (i = 0; i < data_len; i++) {
> +		dev_dbg(&sdev->dev, "%s: data %02x\n", __func__, (unsigned int)((const u8*)data)[i]);
> +	}
> +
> +	ret = serdev_device_write_buf(sdev, buf, 4);
> +	if (ret < 0)
> +		return ret;
> +	if (ret != 4)
> +		return -EIO;
> +
> +	if (data_len) {
> +		ret = serdev_device_write_buf(sdev, data, data_len);
> +		if (ret < 0)
> +			return ret;
> +		if (ret != data_len)
> +			return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static int picogw_recv_answer(struct picogw_device *picodev,
> +	char *cmd, bool *ack, void *buf, int buf_len,
> +	unsigned long timeout)
> +{
> +	int len;
> +
> +	timeout = wait_for_completion_timeout(&picodev->answer_comp, timeout);
> +	if (!timeout)
> +		return -ETIMEDOUT;
> +
> +	if (cmd)
> +		*cmd = picodev->rx_buf[0];
> +
> +	if (ack)
> +		*ack = (picodev->rx_buf[3] == 1);
> +
> +	len = min(picodev->rx_len - 4, buf_len);
> +	if (buf)
> +		memcpy(buf, picodev->rx_buf + 4, len);
> +
> +	reinit_completion(&picodev->answer_comp);
> +	complete(&picodev->answer_read_comp);
> +
> +	return len;
> +}
> +
> +static int picogw_reg_read(struct picogw_device *picodev, u8 addr, u8 *val, unsigned long timeout)
> +{
> +	const u8 dummy = 0;
> +	char cmd;
> +	bool ack;
> +	int ret;
> +
> +	ret = picogw_send_cmd(picodev, 'r', addr, &dummy, false ? 1 : 0);
> +	if (ret)
> +		return ret;
> +
> +	ret = picogw_recv_answer(picodev, &cmd, &ack, val, 1, timeout);
> +	if (ret < 0)
> +		return ret;
> +	if (cmd != 'r')
> +		return -EIO;
> +	if (!ack || ret != 1)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int picogw_reg_write(struct picogw_device *picodev, u8 addr, u8 val, unsigned long timeout)
> +{
> +	char cmd;
> +	bool ack;
> +	int ret;
> +
> +	ret = picogw_send_cmd(picodev, 'w', addr, &val, 1);
> +	if (ret)
> +		return ret;
> +
> +	ret = picogw_recv_answer(picodev, &cmd, &ack, NULL, 0, timeout);
> +	if (ret < 0)
> +		return ret;
> +	if (cmd != 'w')
> +		return -EIO;
> +	if (!ack || ret != 0)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int picogw_mcu_fw_check(struct picogw_device *picodev,
> +	u32 fw_version, u8 *id, unsigned long timeout)
> +{
> +	char cmd;
> +	bool ack;
> +	int ret;
> +
> +	fw_version = cpu_to_be32(fw_version);
> +	ret = picogw_send_cmd(picodev, 'l', 0, &fw_version, sizeof(fw_version));
> +	if (ret)
> +		return ret;
> +
> +	ret = picogw_recv_answer(picodev, &cmd, &ack, id, id ? 8 : 0, timeout);
> +	if (ret < 0)
> +		return ret;
> +	if (cmd != 'l')
> +		return -EIO;
> +	if (id && ret != 8)
> +		return -EIO;
> +
> +	return ack ? 0 : -ENOTSUPP;
> +}
> +
> +static int picogw_regmap_gather_write(void *context,
> +	const void *reg_buf, size_t reg_size, const void *val_buf, size_t val_size)
> +{
> +	struct picogw_device *picodev = context;
> +	const u8 *addr_buf = reg_buf;
> +	const u8 *val = val_buf;
> +	u8 addr;
> +	int ret;
> +
> +	//dev_dbg(&picodev->serdev->dev, "%s: 0x%x (reg_size %zu) 0x%x (val_size %zu)\n",
> +	//	__func__, (unsigned int)addr_buf[0], reg_size, (unsigned int)val[0], val_size);
> +
> +	if (reg_size != 1 || val_size > 0xffff)
> +		return -EINVAL;
> +
> +	addr = addr_buf[0] & ~BIT(7);
> +	if (val_size == 1) {
> +		ret = picogw_reg_write(picodev, addr, val[0], HZ);
> +		if (ret)
> +			return ret;
> +		return 0;
> +	} else {
> +		/* TODO burst mode */
> +		dev_err(&picodev->serdev->dev, "burst mode write not yet implemented\n");
> +		return -ENOTSUPP;
> +	}
> +}
> +
> +static int picogw_regmap_write(void *context,
> +	const void *data_buf, size_t count)
> +{
> +	const u8 *data = data_buf;
> +	if (count < 1)
> +		return -EINVAL;
> +
> +	return picogw_regmap_gather_write(context, data, 1, data + 1, count - 1);
> +}
> +
> +static int picogw_regmap_read(void *context,
> +	const void *reg_buf, size_t reg_size, void *val_buf, size_t val_size)
> +{
> +	struct picogw_device *picodev = context;
> +	const u8 *addr_buf = reg_buf;
> +	u8 addr;
> +	int ret;
> +
> +	//dev_dbg(&picodev->serdev->dev, "%s: 0x%x (reg_size %zu) (val_size %zu)\n", __func__, (unsigned int)addr_buf[0], reg_size, val_size);
> +
> +	if (reg_size != 1 || val_size > 0xffff)
> +		return -EINVAL;
> +
> +	addr = addr_buf[0] & ~BIT(7);
> +	if (val_size == 1) {
> +		ret = picogw_reg_read(picodev, addr, val_buf, HZ);
> +		if (ret)
> +			return ret;
> +		return 0;
> +	} else {
> +		/* TODO burst mode */
> +		dev_err(&picodev->serdev->dev, "burst mode read not yet implemented\n");
> +		return -ENOTSUPP;
> +	}
> +}
> +
> +static const struct regmap_bus picogw_regmap_bus = {
> +	.write = picogw_regmap_write,
> +	.gather_write = picogw_regmap_gather_write,
> +	.read = picogw_regmap_read,
> +
> +	.max_raw_write = 0xffff,
> +	.max_raw_read = 0xffff,
> +};
> +
> +static int picogw_handle_answer(struct picogw_device *picodev)
> +{
> +	struct device *dev = &picodev->serdev->dev;
> +	unsigned int data_len = ((u16)picodev->rx_buf[1] << 8) | picodev->rx_buf[2];
> +	int cmd_len = 4 + data_len;
> +	int i, ret;
> +
> +	if (picodev->rx_len < 4)
> +		return 0;
> +
> +	if (cmd_len > sizeof(picodev->rx_buf)) {
> +		dev_warn(dev, "answer too long (%u)\n", data_len);
> +		return 0;
> +	}
> +
> +	if (picodev->rx_len < cmd_len) {
> +		dev_dbg(dev, "got %u, need %u bytes\n", picodev->rx_len, cmd_len);
> +		return 0;
> +	}
> +
> +	dev_dbg(dev, "Answer %c =%u %s (%u)\n", picodev->rx_buf[0],
> +		(unsigned int)picodev->rx_buf[3],
> +		(picodev->rx_buf[3] == 1) ? "OK" : "K0",
> +		data_len);
> +	for (i = 0; i < data_len; i++) {
> +		//dev_dbg(dev, "%s: %02x\n", __func__, (unsigned int)picodev->rx_buf[4 + i]);
> +	}
> +
> +	complete(&picodev->answer_comp);
> +	ret = wait_for_completion_interruptible_timeout(&picodev->answer_read_comp, HZ / 2);
> +	if (ret < 0)
> +		return 0;
> +
> +	reinit_completion(&picodev->answer_read_comp);
> +
> +	return cmd_len;
> +}
> +
> +static int picogw_receive_buf(struct serdev_device *sdev, const u8 *data, size_t count)
> +{
> +	struct picogw_device *picodev = picogw_get_drvdata(sdev);
> +	size_t i;
> +	int len = 0;
> +
> +	dev_dbg(&sdev->dev, "Receive (%zu)\n", count);
> +
> +	if (completion_done(&picodev->answer_comp)) {
> +		dev_info(&sdev->dev, "RX waiting on completion\n");
> +		return 0;
> +	}
> +	if (picodev->rx_len == sizeof(picodev->rx_buf)) {
> +		dev_warn(&sdev->dev, "RX buffer full\n");
> +		return 0;
> +	}
> +
> +	i = min(count, sizeof(picodev->rx_buf) - picodev->rx_len);
> +	if (i > 0) {
> +		memcpy(&picodev->rx_buf[picodev->rx_len], data, i);
> +		picodev->rx_len += i;
> +		len += i;
> +	}
> +
> +	while (picodev->rx_len > 0) {
> +		/* search for valid beginning */
> +		for (i = 0; i < picodev->rx_len; i++) {
> +			if (picogw_valid_cmd(picodev->rx_buf[i]))
> +				break;
> +		}
> +		if (i > 0) {
> +			dev_dbg(&sdev->dev, "skipping %zu bytes of garbage\n", i);
> +			if (i < picodev->rx_len) {
> +				memmove(picodev->rx_buf, &picodev->rx_buf[i], picodev->rx_len - i);
> +				picodev->rx_len -= i;
> +			} else
> +				picodev->rx_len = 0;
> +		}
> +
> +		i = picogw_handle_answer(picodev);
> +		if (i == 0)
> +			break;
> +
> +		if (i % 64 == 0) {
> +			dev_info(&sdev->dev, "skipping padding byte\n");
> +			i++;
> +		}
> +		if (picodev->rx_len > i)
> +			memmove(picodev->rx_buf, &picodev->rx_buf[i], picodev->rx_len - i);
> +		if (picodev->rx_len >= i)
> +			picodev->rx_len -= i;
> +	}
> +
> +	return len;
> +}
> +
> +static const struct serdev_device_ops picogw_serdev_client_ops = {
> +	.receive_buf = picogw_receive_buf,
> +	.write_wakeup = serdev_device_write_wakeup,
> +};
> +
> +static int picogw_serdev_probe(struct serdev_device *sdev)
> +{
> +	struct picogw_device *picodev;
> +	struct regmap *regmap;
> +	u32 fw_version = 0x010a0006;

Worth moving the version to a define?

> +	u8 mac[8];here
> +	int ret;
> +
> +	//dev_info(&sdev->dev, "Probing\n");
> +
> +	picodev = devm_kzalloc(&sdev->dev, sizeof(*picodev), GFP_KERNEL);
> +	if (!picodev)
> +		return -ENOMEM;
> +
> +	picodev->serdev = sdev;
> +	init_completion(&picodev->answer_comp);
> +	init_completion(&picodev->answer_read_comp);
> +
> +	ret = serdev_device_open(sdev);
> +	if (ret) {
> +		dev_err(&sdev->dev, "Failed to open (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	serdev_device_set_baudrate(sdev, 115200);
> +	serdev_device_set_parity(sdev, SERDEV_PARITY_NONE);
> +	serdev_device_set_flow_control(sdev, true);
> +
> +	regmap = devm_regmap_init(&sdev->dev, &picogw_regmap_bus, picodev, &sx130x_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		ret = PTR_ERR(regmap);
> +		dev_err(&sdev->dev, "error initializing regmap (%d)\n", ret);
> +		serdev_device_close(sdev);
> +		return ret;
> +	}
> +
> +	ret = sx130x_early_probe(regmap, NULL);
> +	if (ret) {
> +		serdev_device_close(sdev);
> +		return ret;
> +	}
> +
> +	sx130x_set_drvdata(&sdev->dev, picodev);
> +	serdev_device_set_client_ops(sdev, &picogw_serdev_client_ops);
> +
> +	//msleep(1000);
> +	ret = picogw_mcu_fw_check(picodev, fw_version, mac, HZ);
> +	if (!ret || ret == -ENOTSUPP)
> +		dev_info(&sdev->dev, "ID = %02x%02x%02x%02x%02x%02x%02x%02x\n",
> +			(unsigned int)mac[0],
> +			(unsigned int)mac[1],
> +			(unsigned int)mac[2],
> +			(unsigned int)mac[3],
> +			(unsigned int)mac[4],
> +			(unsigned int)mac[5],
> +			(unsigned int)mac[6],
> +			(unsigned int)mac[7]);
> +	while (ret == -ENOTSUPP && ((fw_version & 0xff) > 4)) {
> +		ret = picogw_mcu_fw_check(picodev, --fw_version, NULL, HZ);
> +	}
> +	if (ret == -ENOTSUPP) {
> +		dev_warn(&sdev->dev, "firmware check failed (%08x)\n", fw_version);
> +	} else {
> +		dev_err(&sdev->dev, "ID retrieval failed (%d)\n", ret);
> +		serdev_device_close(sdev);
> +		return ret;
> +	}
> +
> +	ret = sx130x_probe(&sdev->dev);
> +	if (ret) {
> +		serdev_device_close(sdev);
> +		return ret;
> +	}
> +
> +	//dev_info(&sdev->dev, "Done.\n");
> +
> +	return 0;
> +}
> +
> +static void picogw_serdev_remove(struct serdev_device *sdev)
> +{
> +	sx130x_remove(&sdev->dev);
> +
> +	serdev_device_close(sdev);
> +
> +	//dev_info(&sdev->dev, "Removed\n");
> +}
> +
> +static const struct of_device_id picogw_serdev_of_match[] = {
> +	{ .compatible = "semtech,lora-picocell" },

lora-picocell or lora-picogw... picocell has mobile connotations, should 
we match the module name?

> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, picogw_serdev_of_match);
> +
> +static struct serdev_device_driver picogw_serdev_driver = {
> +	.probe = picogw_serdev_probe,
> +	.remove = picogw_serdev_remove,
> +	.driver = {
> +		.name = "lora-picogw",
> +		.of_match_table = picogw_serdev_of_match,
> +	},
> +};
> +
> +static int __init picogw_serdev_init(void)
> +{
> +	int ret;
> +
> +	ret = serdev_device_driver_register(&picogw_serdev_driver);
> +	if (ret) {
> +		pr_err("serdev_device_driver_register failed (%d)", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +module_init(picogw_serdev_init);
> +
> +static void __exit picogw_serdev_exit(void)
> +{
> +	serdev_device_driver_unregister(&picogw_serdev_driver);
> +}
> +module_exit(picogw_serdev_exit);
> +
> +MODULE_LICENSE("GPL");
> 

Thanks,
Ben Whitten

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