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Message-ID: <YmgDID8pRYDFK8vi@google.com>
Date: Tue, 26 Apr 2022 15:35:12 +0100
From: Lee Jones <lee.jones@...aro.org>
To: frank zago <frank@...o.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bgolaszewski@...libre.com>,
Wolfram Sang <wsa@...nel.org>, Johan Hovold <johan@...nel.org>,
linux-usb@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>,
linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v5 1/3] mfd: ch341: add core driver for the WCH CH341 in
I2C/SPI/GPIO mode
On Thu, 31 Mar 2022, frank zago wrote:
> 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@...o.net>
> ---
> Documentation/misc-devices/ch341.rst | 114 +++++++++++++++++++++++++++
> Documentation/misc-devices/index.rst | 1 +
Not sure I've seen this bundled with an MFD driver before.
Please separate them into their own patches.
> MAINTAINERS | 7 ++
> drivers/mfd/Kconfig | 10 +++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/ch341-core.c | 99 +++++++++++++++++++++++
> include/linux/mfd/ch341.h | 26 ++++++
> 7 files changed, 258 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..bf0b83f2eb85
> --- /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 ch341 MFD drivers
> + - 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 devices 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..52d03715601e 100644
> --- a/Documentation/misc-devices/index.rst
> +++ b/Documentation/misc-devices/index.rst
> @@ -19,6 +19,7 @@ fit into other categories.
> bh1770glc
> eeprom
> c2port
> + ch341
> dw-xdata-pcie
> ibmvmc
> ics932s401
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cbbd3ce7e0c2..b61af813fb9f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21211,6 +21211,13 @@ M: David Härdeman <david@...deman.nu>
> S: Maintained
> F: drivers/media/rc/winbond-cir.c
>
> +WINCHIPHEAD CH341 I2C/GPIO MFD DRIVER
> +M: Frank Zago <frank@...o.net>
> +L: linux-usb@...r.kernel.org
> +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@...il.com>
> L: linux-watchdog@...r.kernel.org
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 3b59456f5545..893acc821a42 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1784,6 +1784,16 @@ 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.
> +
> + 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 858cacf659d6..fd615ab3929f 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..0bb6eb8057e9
> --- /dev/null
> +++ b/drivers/mfd/ch341-core.c
> @@ -0,0 +1,99 @@
> +// 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@...orcht.net)
> + * Copyright (c) 2016 Tse Lun Bien
> + * Copyright (c) 2014 Marco Gittler
> + * Copyright (c) 2006-2007 Till Harbaum (Till@...baum.org)
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/mfd/ch341.h>
> +#include <linux/mfd/core.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/usb.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;
Please rename this struct 'ch341_ddata' and s/dev/ddata/.
> + int rc;
'ret' please.
> + dev = devm_kzalloc(&iface->dev, sizeof(*dev), GFP_KERNEL);
> + if (!dev)
> + return -ENOMEM;
> +
> + dev->usb_dev = usb_get_dev(interface_to_usbdev(iface));
Can this come later?
It would save on the goto dance.
> + dev->iface = iface;
> + mutex_init(&dev->usb_lock);
> +
> + if (iface->cur_altsetting->desc.bNumEndpoints != 3) {
Why 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)) {
What has happened if we get here?
Perhaps a comment would be useful?
> + 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,
Why are you using 'hotplug' here?
ch341_devs is empty right?
So no child devices are registered.
In which case this is not (yet) an MFD and cannot be accepted.
Please add the children.
> + ARRAY_SIZE(ch341_devs));
> + if (rc) {
> + rc = dev_err_probe(&iface->dev, rc,
> + "Failed to add mfd devices to core\n");
I'm not even sure what this means. Should be:
"Failed to register child devices\n"
> + goto free_dev;
> + }
> +
> + return 0;
> +
> +free_dev:
> + usb_put_dev(dev->usb_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_put_dev(dev->usb_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");
This does not look valid. Please drop it.
> +MODULE_DESCRIPTION("CH341 USB to I2C/SPI/GPIO adapter");
Is it? What makes it one of those?
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/mfd/ch341.h b/include/linux/mfd/ch341.h
> new file mode 100644
> index 000000000000..a87b23e30123
> --- /dev/null
> +++ b/include/linux/mfd/ch341.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Definitions for the CH341 MFD driver */
Drop the term MFD please.
> +#include <linux/mutex.h>
> +#include <linux/types.h>
> +
> +#define DEFAULT_TIMEOUT_MS 1000 /* 1s USB requests timeout */
Where is this used?
> +/* All commands fit inside a 32-byte segment. There may be several
> + * of these segments in a USB command.
> + */
This is not a properly formatted multi-line comment.
> +#define SEG_SIZE 32
> +
> +struct usb_device;
> +struct usb_interface;
> +
> +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;
> +};
--
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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