Re: [PATCH] usb: typec: ucsi: acpi: Assume UCSI 1.0 on Lenovo ThinkPad T14 Gen 2a

["Mark Pearson" <mpearson-lenovo@squebb.ca>]

Hi Stanislaw,

On Sat, Oct 31, 2026, at 5:40 PM, Stanisław Titenko via B4 Relay wrote:
> From: Stanisław Titenko <kernel@resetko.pl>
>
> The Lenovo ThinkPad T14 Gen 2a exposes a functional UCSI ACPI PPM but
> the firmware leaves the VERSION field of the UCSI mailbox at zero.
>
> ucsi_register() rejects a zero version with -ENODEV, leaving the
> system without registered USB Type-C connectors. Without an OPM, the
> embedded controller does not complete DisplayPort Alternate Mode setup
> when a USB-C dock or monitor that supplies power is connected after
> boot, so the display stays dark while USB and charging work.
>
> The mailbox uses the 48-byte UCSI 1.x layout, and the PPM works
> correctly when UCSI 1.0 is assumed.
>
> Add a DMI-specific UCSI operation for the ThinkPad T14 Gen 2a that
> substitutes UCSI 1.0 only when firmware reports a zero version.
> Preserve any valid non-zero firmware version.
>
> Tested on a ThinkPad T14 Gen 2a with BIOS 1.33 (R1MET63W): both
> Type-C connectors register, and plugging and replugging a USB-C
> monitor with an integrated hub and power delivery brings up
> DisplayPort Alternate Mode each time.
>
> Reported-by: Daniel Dev <daniel.dev@noex.uk>
> Closes: 
> https://lore.kernel.org/linux-usb/b1Wn_eFvTFShGbd970WWl4CWhge_6P2x7Wb6rab3QHNlE4OJ4p__O-QN3B6I-308ftr5oV5Zr7vywA0vdvmtNw6E0YJnVM2ek_5DcFnkXB0=@noex.uk/
> Fixes: c1b0bc2dabfa ("usb: typec: Add support for UCSI interface")
> Cc: stable@vger.kernel.org
> Assisted-by: pi:claude-opus-5-5
> Signed-off-by: Stanisław Titenko <kernel@resetko.pl>

This platform was Linux certified so let me see if I can get the FW team to look at it (it is an older platform, but it looks like it's still under support)
I don't have this HW myself, so I'll need to ask the team in Japan to reproduce the issue. My personal preference would be to try and get the FW fixed first and do the quirk if for some reason that isn't possible.

> ---
>  drivers/usb/typec/ucsi/ucsi_acpi.c | 34 
> ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
>
> diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c 
> b/drivers/usb/typec/ucsi/ucsi_acpi.c
> index 5697ccc24ec3..33747e24353f 100644
> --- a/drivers/usb/typec/ucsi/ucsi_acpi.c
> +++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
> @@ -148,6 +148,33 @@ static const struct ucsi_operations ucsi_acer_ops 
> = {
>  	.async_control = ucsi_acpi_async_control
>  };
> 
> +static int ucsi_lenovo_read_version(struct ucsi *ucsi, u16 *version)
> +{
> +	struct ucsi_acpi *ua = ucsi_get_drvdata(ucsi);
> +	int ret;
> +
> +	ret = ucsi_acpi_read_version(ucsi, version);
> +	if (ret)
> +		return ret;
> +
> +	if (!*version) {
> +		dev_warn(ua->dev, "UCSI version is zero, assuming 1.0\n");
> +		*version = UCSI_VERSION_1_0;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct ucsi_operations ucsi_lenovo_ops = {
> +	.read_version = ucsi_lenovo_read_version,
> +	.read_cci = ucsi_acpi_read_cci,
> +	.poll_cci = ucsi_acpi_poll_cci,
> +	.read_message_in = ucsi_acpi_read_message_in,
> +	.write_message_out = ucsi_acpi_write_message_out,
> +	.sync_control = ucsi_sync_control_common,
> +	.async_control = ucsi_acpi_async_control
> +};
> +
>  static int ucsi_gram_sync_control(struct ucsi *ucsi, u64 command, u32 *cci,
>  				  void *val, size_t len, void *msg_out,
>  				  size_t msg_out_size)
> @@ -196,6 +223,13 @@ static const struct dmi_system_id ucsi_acpi_quirks[] = {
>  		},
>  		.driver_data = (void *)&ucsi_acer_ops,
>  	},
> +	{
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> +			DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T14 Gen 2a"),
> +		},
> +		.driver_data = (void *)&ucsi_lenovo_ops,
> +	},
>  	{
>  		.matches = {
>  			DMI_MATCH(DMI_SYS_VENDOR, "LG Electronics"),
>

1) Couldn't you just reuse the ucsi_acer_ops quirk?

2) Better to use DMI_BOARD_NAME for the DMI match. For the T14 G2 AMD there are two possible matches - "20XK" and "20XL".

Thanks
Mark