[PATCH v4 1/3] mfd: ch341: add core driver for the WCH CH341 in I2C/GPIO mode

From: frank zago
Date: Mon Mar 21 2022 - 00:32:03 EST

The CH341 is a multifunction chip, presenting 3 different USB PID. One
of these functions is for I2C/SPI/GPIO. This new set of drivers will
manage I2C and GPIO.

Signed-off-by: frank zago <frank@xxxxxxxx>
---
Documentation/misc-devices/ch341.rst | 114 +++++++++++++++++++++++++++
Documentation/misc-devices/index.rst | 1 +
MAINTAINERS | 7 ++
drivers/mfd/Kconfig | 12 +++
drivers/mfd/Makefile | 1 +
drivers/mfd/ch341-core.c | 103 ++++++++++++++++++++++++
include/linux/mfd/ch341.h | 25 ++++++
7 files changed, 263 insertions(+)
create mode 100644 Documentation/misc-devices/ch341.rst
create mode 100644 drivers/mfd/ch341-core.c
create mode 100644 include/linux/mfd/ch341.h

diff --git a/Documentation/misc-devices/ch341.rst b/Documentation/misc-devices/ch341.rst
new file mode 100644
index 000000000000..a4884918cd32
--- /dev/null
+++ b/Documentation/misc-devices/ch341.rst
@@ -0,0 +1,114 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+===========================================================
+WinChipHead (沁恒) CH341 linux driver for I2C and GPIO mode
+===========================================================
+
+The CH341 is declined in several flavors, and may support one or more
+of UART, SPI, I2C and GPIO, but not always simultaneously:
+
+ - CH341 A/B/F: UART, Printer, SPI, I2C and GPIO
+ - CH341 C/T: UART and I2C
+ - CH341 H: SPI
+
+They work in 3 different modes, with only one being presented
+depending on the USB PID:
+
+ - 0x5523: UART mode, covered by the USB `ch341` serial driver
+ - 0x5512: SPI/I2C/GPIO mode, covered by the MFD `ch341-mfd` driver
+ - 0x5584: Parallel printer mode, covered by the USB `usblp` driver
+
+Mode selection is done at the hardware level by tying some
+pins. Breakout boards with one of the CH341 chip usually have one or
+more jumpers to select which mode they work on. At least one model
+(CJMCU-341) appears to need bridging some solder pads to select a
+different default. Breakout boards also don't usually offer an option
+to configure the chip into printer mode; for that case, connect the
+SCL and SDA lines directly together.
+
+The various CH341 appear to be indistinguishable from the
+software. For instance the ch341 MFD driver will present a GPIO
+interface for the CH341T although physical pins are not present, and
+the device will accept GPIO commands.
+
+The ch341 MFD driver has been tested with a CH341A, CH341B and
+CH341T.
+
+Some breakout boards work in 3.3V and 5V depending on some jumpers.
+
+The black chip programmer with a ZIF socket will power the CH341 at
+3.3V if a jumper is set, but will only output 5V to the chips to be
+programmed, which is not always desirable. A hardware hack to use 3.3V
+everywhere, involving some soldering, is available at
+https://eevblog.com/forum/repair/ch341a-serial-memory-programmer-power-supply-fix/
+
+Some sample code for the CH341 is available at the manufacturer
+website, at http://wch-ic.com/products/CH341.html
+
+The repository at https://github.com/boseji/CH341-Store contains a lot
+of information on these chips, including datasheets.
+
+This driver is based on the pre-existing work at
+https://github.com/gschorcht/i2c-ch341-usb
+
+
+I2C Caveats
+-----------
+
+The ch341 doesn't work with a Wii nunchuk, possibly because the
+pull-up value is too low (1500 ohms).
+
+i2c AT24 eeproms can be read but not programmed properly because the
+at24 linux driver tries to write a byte at a time, and doesn't wait at
+all (or enough) between writes. Data corruption on writes does occur.
+
+The driver doesn't support detection of I2C device present on the
+bus. Apparently when a device is not present at a given address, the
+CH341 will return an extra byte of data, but the driver doesn't
+support that. This may be addressed in the future.
+
+
+The GPIOs
+---------
+
+16 GPIOs are available on the CH341 A/B/F. The first 6 are input/output,
+and the last 10 are input only.
+
+Pinout and their names as they appear on some breakout boards::
+
+ CH341A/B/F GPIO Names Mode
+ pin line
+
+ 15 0 D0, CS0 input/output
+ 16 1 D1, CS1 input/output
+ 17 2 D2, CS2 input/output
+ 18 3 D3, SCK, DCK input/output
+ 19 4 D4, DOUT2, CS3 input/output
+ 20 5 D5, MOSI, DOUT, SDO input/output
+ 21 6 D6, DIN2 input
+ 22 7 D7, MISO, DIN input
+ 5 8 ERR input
+ 6 9 PEMP input
+ 7 10 INT input
+ 8 11 SLCT (SELECT) input
+ 26 12 RST# (?) input
+ 27 13 WT (WAIT) input
+ 4 14 DS (Data Select?) input
+ 3 15 AS (Address Select?) input
+
+
+GPIO interrupt
+~~~~~~~~~~~~~~
+
+The INT pin, corresponding to GPIO 10 is an input pin that can trigger
+an interrupt on a rising edge. Only that pin is able to generate an
+interrupt, and only on a rising edge. Trying to monitor events on
+another GPIO, or that GPIO on something other than a rising edge, will
+be rejected.
+
+
+SPI
+---
+
+This driver doesn't offer an SPI interface (yet) due to the
+impossibility of declaring an SPI device like I2C does.
diff --git a/Documentation/misc-devices/index.rst b/Documentation/misc-devices/index.rst
index 30ac58f81901..190f93b56ec6 100644
--- a/Documentation/misc-devices/index.rst
+++ b/Documentation/misc-devices/index.rst
@@ -29,3 +29,4 @@ fit into other categories.
spear-pcie-gadget
uacce
xilinx_sdfec
+ ch341
diff --git a/MAINTAINERS b/MAINTAINERS
index cd0f68d4a34a..a6b2805fd1a1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20845,6 +20845,13 @@ M: David Härdeman <david@xxxxxxxxxxx>
S: Maintained
F: drivers/media/rc/winbond-cir.c

+WINCHIPHEAD CH341 I2C/GPIO MFD DRIVER
+M: Frank Zago <frank@xxxxxxxx>
+L: linux-usb@xxxxxxxxxxxxxxx
+S: Maintained
+F: drivers/mfd/ch341-core.c
+F: include/linux/mfd/ch341.h
+
WINSYSTEMS EBC-C384 WATCHDOG DRIVER
M: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
L: linux-watchdog@xxxxxxxxxxxxxxx
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index ba0b3eb131f1..84067e454c90 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1778,6 +1778,18 @@ config MFD_LOCHNAGAR
help
Support for Cirrus Logic Lochnagar audio development board.

+config MFD_CH341
+ tristate "WinChipHead CH341 in I2C/SPI/GPIO mode"
+ depends on USB
+ help
+ If you say yes to this option, support for the CH341 series
+ of chips, running in I2C/SPI/GPIO mode will be included.
+
+ The chip's SPI mode is not supported.
+
+ This driver can also be built as a module. If so, the
+ module will be called ch341-core.
+
config MFD_ARIZONA
select REGMAP
select REGMAP_IRQ
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index df1ecc4a4c95..a0364a0d5e33 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_MFD_ASIC3) += asic3.o tmio_core.o
obj-$(CONFIG_ARCH_BCM2835) += bcm2835-pm.o
obj-$(CONFIG_MFD_BCM590XX) += bcm590xx.o
obj-$(CONFIG_MFD_BD9571MWV) += bd9571mwv.o
+obj-$(CONFIG_MFD_CH341) += ch341-core.o
obj-$(CONFIG_MFD_CROS_EC_DEV) += cros_ec_dev.o
obj-$(CONFIG_MFD_ENE_KB3930) += ene-kb3930.o
obj-$(CONFIG_MFD_EXYNOS_LPASS) += exynos-lpass.o
diff --git a/drivers/mfd/ch341-core.c b/drivers/mfd/ch341-core.c
new file mode 100644
index 000000000000..fbb2897cd956
--- /dev/null
+++ b/drivers/mfd/ch341-core.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Core driver for the CH341A, CH341B and CH341T in I2C/SPI/GPIO
+ * mode. There are cell drivers available for I2C and GPIO. SPI is not
+ * yet supported.
+ *
+ * Copyright 2022, Frank Zago
+ * Copyright (c) 2017 Gunar Schorcht (gunar@xxxxxxxxxxxx)
+ * Copyright (c) 2016 Tse Lun Bien
+ * Copyright (c) 2014 Marco Gittler
+ * Copyright (c) 2006-2007 Till Harbaum (Till@xxxxxxxxxxx)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mfd/core.h>
+
+#include <linux/mfd/ch341.h>
+
+static const struct mfd_cell ch341_devs[] = {
+};
+
+static int ch341_usb_probe(struct usb_interface *iface,
+ const struct usb_device_id *usb_id)
+{
+ struct usb_host_endpoint *endpoints;
+ struct ch341_device *dev;
+ int rc;
+
+ dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+ if (!dev)
+ return -ENOMEM;
+
+ dev->usb_dev = usb_get_dev(interface_to_usbdev(iface));
+ dev->iface = iface;
+ mutex_init(&dev->usb_lock);
+
+ if (iface->cur_altsetting->desc.bNumEndpoints != 3) {
+ rc = -ENODEV;
+ goto free_dev;
+ }
+
+ endpoints = iface->cur_altsetting->endpoint;
+ if (!usb_endpoint_is_bulk_in(&endpoints[0].desc) ||
+ !usb_endpoint_is_bulk_out(&endpoints[1].desc) ||
+ !usb_endpoint_xfer_int(&endpoints[2].desc)) {
+ rc = -ENODEV;
+ goto free_dev;
+ }
+
+ dev->ep_in = endpoints[0].desc.bEndpointAddress;
+ dev->ep_out = endpoints[1].desc.bEndpointAddress;
+ dev->ep_intr = endpoints[2].desc.bEndpointAddress;
+ dev->ep_intr_interval = endpoints[2].desc.bInterval;
+
+ usb_set_intfdata(iface, dev);
+
+ rc = mfd_add_hotplug_devices(&iface->dev, ch341_devs,
+ ARRAY_SIZE(ch341_devs));
+ if (rc) {
+ dev_err(&iface->dev, "Failed to add mfd devices to core.");
+ goto free_dev;
+ }
+
+ return 0;
+
+free_dev:
+ usb_put_dev(dev->usb_dev);
+ kfree(dev);
+
+ return rc;
+}
+
+static void ch341_usb_disconnect(struct usb_interface *usb_if)
+{
+ struct ch341_device *dev = usb_get_intfdata(usb_if);
+
+ mfd_remove_devices(&usb_if->dev);
+ usb_set_intfdata(dev->iface, NULL);
+ usb_put_dev(dev->usb_dev);
+ kfree(dev);
+}
+
+static const struct usb_device_id ch341_usb_table[] = {
+ { USB_DEVICE(0x1a86, 0x5512) },
+ { }
+};
+
+MODULE_DEVICE_TABLE(usb, ch341_usb_table);
+
+static struct usb_driver ch341_usb_driver = {
+ .name = "ch341-mfd",
+ .id_table = ch341_usb_table,
+ .probe = ch341_usb_probe,
+ .disconnect = ch341_usb_disconnect
+};
+
+module_usb_driver(ch341_usb_driver);
+
+MODULE_AUTHOR("Various");
+MODULE_DESCRIPTION("CH341 USB to I2C/SPI/GPIO adapter");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/ch341.h b/include/linux/mfd/ch341.h
new file mode 100644
index 000000000000..246159477cdf
--- /dev/null
+++ b/include/linux/mfd/ch341.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Definitions for CH341 MFD driver
+ */
+
+#include <linux/usb.h>
+#include <linux/mutex.h>
+
+#define DEFAULT_TIMEOUT 1000 /* 1s USB requests timeout */
+
+/* All commands fit inside a 32-byte segment. There may be several
+ * of these segments in a USB command.
+ */
+#define SEG_SIZE 32
+
+struct ch341_device {
+ struct usb_device *usb_dev;
+ struct usb_interface *iface;
+ struct mutex usb_lock;
+
+ int ep_in;
+ int ep_out;
+ int ep_intr;
+ u8 ep_intr_interval;
+};
--
2.32.0