Re: [PATCH] platform/x86: Add new MeeGoPad ANX7428 Type-C Cross Switch driver

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On Sun, Feb 11, 2024 at 9:53 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Some MeeGoPad top-set boxes have an ANX7428 Type-C Switch for USB3.1 Gen 1
> and DisplayPort over Type-C alternate mode support.
>
> The ANX7428 has a microcontroller which takes care of the PD negotiation
> and automatically sets the builtin Crosspoint Switch to send the right
> signal to the 4 highspeed pairs of the Type-C connector. It also takes
> care of HPD and AUX channel routing for DP alternate mode.
>
> IOW the ANX7428 operates fully autonomous and to the x5-Z8350 SoC
> things look like there simple is a USB-3 Type-A connector and a
> separate DipslayPort connector. Except that the BIOS does not

DisplayPort

> power on the ANX7428 at boot (meh).
>
> Add a driver to power on the ANX7428. This driver is added under
> drivers/platform/x86 rather then under drivers/usb/typec for 2 reasons:

than

> 1. This driver is specificly written to work with how the ANX7428 is

specifically

> described in the ACPI tables of the MeeGoPad x86 (Cherry Trail) devices.
>
> 2. This driver only powers on the ANX7428 and does not do anything wrt
> its Type-C functionality. It should be possible to tell the controller
> which data- and/or power-role to negotiate and to swap the role(s) after
> negotiation but the MeeGoPad top-set boxes always draw their power from
> a separate power-connector and they only support USB host-mode. So this
> functionality is unnecessary and due to lack of documenation this

documentation

> is tricky to support.

...

> +/*
> + * meegopad_anx7428.c - Driver to power on the Analogix ANX7428

Keeping a filename inside the file is a burden in case the file gets
renamed in the future.

> + * USB Type-C crosspoint switch on MeeGoPad top-set boxes.
> + *
> + * The MeeGoPad T8 and T9 are Cherry Trail top-set boxes which
> + * use an ANX7428 to provide a Type-C port with USB3.1 Gen 1 and
> + * DisplayPort over Type-C alternate mode support.
> + *
> + * The ANX7428 has a microcontroller which takes care of the PD
> + * negotiation and automatically sets the builtin Crosspoint Switch
> + * to send the right signal to the 4 highspeed pairs of the Type-C
> + * connector. It also takes care of HPD and AUX channel routing for
> + * DP alternate mode.
> + *
> + * IOW the ANX7428 operates fully autonomous and to the x5-Z8350 SoC
> + * things look like there simple is a USB-3 Type-A connector and a
> + * separate DipslayPort connector. Except that the BIOS does not

DisplayPort

> + * power on the ANX7428 at boot. This driver takes care of powering
> + * on the ANX7428.
> + *
> + * It should be possible to tell the micro-controller which data- and/or
> + * power-role to negotiate and to swap the role(s) after negotiation
> + * but the MeeGoPad top-set boxes always draw their power from a separate
> + * power-connector and they only support USB host-mode. So this functionality
> + * is unnecessary and due to lack of documenation this is tricky to support.

documentation

> + * For a more complete ANX7428 driver see drivers/usb/misc/anx7418/ of
> + * the LineageOS kernel for the LG G5 (International) aka the LG H850:
> + * https://github.com/LineageOS/android_kernel_lge_msm8996/
> + *
> + * (C) Copyright 2024 Hans de Goede <hansg@xxxxxxxxxx>
> + */
> +
> +#include <linux/acpi.h>

+ bits.h

> +#include <linux/delay.h>
> +#include <linux/dmi.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>

...

> +#define VENDOR_ID_L                    0x00
> +#define VENDOR_ID_H                    0x01
> +#define DEVICE_ID_L                    0x02
> +#define DEVICE_ID_H                    0x03

You use word (16-bit) access, why do we need to know these?
Just define them without suffixes (and if you want add a comment that
they are 16-bit LE).

...

> +       usleep_range(10000, 15000);

fsleep() ?

...

> +       /* Wait for the OCM (On Chip Microcontroller) to start */
> +       for (i = 0; i < max_tries; i++) {
> +               usleep_range(5000, 10000);
> +
> +               ret = i2c_smbus_read_byte_data(client, TX_STATUS);
> +               if (ret < 0)
> +                       dev_err_probe(dev, ret, "reading status register\n");
> +               else if (ret & OCM_STARTUP)
> +                       break;
> +       }
> +       if (i == max_tries)
> +               return dev_err_probe(dev, -EIO,
> +                                    "On Chip Microcontroller did not start, status: 0x%02x\n",
> +                                    ret);

Why not use read_poll_timeout() / readx_poll_timeout() (whichever suits better)?

...

> +static struct i2c_driver anx7428_driver = {
> +       .driver = {
> +               .name = KBUILD_MODNAME,

Strictly speaking this is an ABI and we don't want it to be changed in
case of filename change. Personally I _always_ prefer it be open
coded.

> +               .acpi_match_table = anx7428_acpi_match,
> +       },
> +       .probe = anx7428_probe,
> +};

-- 
With Best Regards,
Andy Shevchenko





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