[PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

[PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

[Konrad Dybcio]

From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

The value has been amended with the release of the USB Type-C
Specification v2.1, reportedly as an erratum.

Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
I bundled a change to the CrOS EC driver based on the assumption that
it worked around the faulty definition. I see the Intel PMC mux driver
also checks for this bit, but it seems like that driver assumes that
the value is in-spec (i.e. it may be buggy as of right now).

Adding the respective maintainers to make sure everyone can see this.
---
 drivers/platform/chrome/cros_ec_typec.c | 2 +-
 include/linux/usb/typec_tbt.h           | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index b712bcff6fb2674ec79286159090df6d79b32e9a..d80f3de1b87c362a2825bd19f826c5be077583aa 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -585,7 +585,7 @@ static int cros_typec_enable_tbt(struct cros_typec_data *typec,
 	data.device_mode = TBT_MODE;
 
 	if (pd_ctrl->control_flags & USB_PD_CTRL_TBT_LEGACY_ADAPTER)
-		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_TBT3);
+		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_LEGACY);
 
 	/* Cable Discover Mode VDO */
 	data.cable_mode = TBT_MODE;
diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
index 55dcea12082c80defeb6f199ad333279b58adcd7..6bf208c9dd5037f162678bc0be5be7ae1ca0deca 100644
--- a/include/linux/usb/typec_tbt.h
+++ b/include/linux/usb/typec_tbt.h
@@ -27,8 +27,8 @@ struct typec_thunderbolt_data {
 /* TBT3 Device Discover Mode VDO bits */
 #define TBT_MODE			BIT(0)
 #define TBT_ADAPTER(_vdo_)		FIELD_GET(BIT(16), _vdo_)
-#define   TBT_ADAPTER_LEGACY		0
-#define   TBT_ADAPTER_TBT3		1
+#define   TBT_ADAPTER_TBT3		0
+#define   TBT_ADAPTER_LEGACY		1
 #define TBT_INTEL_SPECIFIC_B0		BIT(26)
 #define TBT_VENDOR_SPECIFIC_B0		BIT(30)
 #define TBT_VENDOR_SPECIFIC_B1		BIT(31)

---
base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb
change-id: 20250926-topic-tbt_header_bit_fix-17aeb524df4a

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

[Tzung-Bi Shih]

On Fri, Sep 26, 2025 at 02:32:57PM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> 
> The value has been amended with the release of the USB Type-C
> Specification v2.1, reportedly as an erratum.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
> I bundled a change to the CrOS EC driver based on the assumption that
> it worked around the faulty definition. I see the Intel PMC mux driver
> also checks for this bit, but it seems like that driver assumes that
> the value is in-spec (i.e. it may be buggy as of right now).
> 
> Adding the respective maintainers to make sure everyone can see this.

I have no context to review the patch.  However, the prefix of patch title
should be "platform/chrome: cros_ec_typec:".


Hi CHROMEOS EC USB TYPE-C maintainers,

Does the patch make sense to you?

Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

[Jameson Thies]

Hi Konrad,
thanks for raising this. Yes, it looks like this works around the
current faulty definitions in typec_tbt.h. Where
pd_ctrl->control_flags is assigned in our EC firmware, the
USB_PD_CTRL_TBT_LEGACY_ADAPTER correctly gets set to 1 for TBT2 legacy
adapters. So the data.device_mode assignment you are updating here is
currently correct even though the macro is incorrect. Your patch LGTM.

Re: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

[Heikki Krogerus]

On Fri, Sep 26, 2025 at 02:32:57PM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> 
> The value has been amended with the release of the USB Type-C
> Specification v2.1, reportedly as an erratum.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Makes sense to me. FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> I bundled a change to the CrOS EC driver based on the assumption that
> it worked around the faulty definition. I see the Intel PMC mux driver
> also checks for this bit, but it seems like that driver assumes that
> the value is in-spec (i.e. it may be buggy as of right now).
> 
> Adding the respective maintainers to make sure everyone can see this.
> ---
>  drivers/platform/chrome/cros_ec_typec.c | 2 +-
>  include/linux/usb/typec_tbt.h           | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index b712bcff6fb2674ec79286159090df6d79b32e9a..d80f3de1b87c362a2825bd19f826c5be077583aa 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -585,7 +585,7 @@ static int cros_typec_enable_tbt(struct cros_typec_data *typec,
>  	data.device_mode = TBT_MODE;
>  
>  	if (pd_ctrl->control_flags & USB_PD_CTRL_TBT_LEGACY_ADAPTER)
> -		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_TBT3);
> +		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_LEGACY);
>  
>  	/* Cable Discover Mode VDO */
>  	data.cable_mode = TBT_MODE;
> diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
> index 55dcea12082c80defeb6f199ad333279b58adcd7..6bf208c9dd5037f162678bc0be5be7ae1ca0deca 100644
> --- a/include/linux/usb/typec_tbt.h
> +++ b/include/linux/usb/typec_tbt.h
> @@ -27,8 +27,8 @@ struct typec_thunderbolt_data {
>  /* TBT3 Device Discover Mode VDO bits */
>  #define TBT_MODE			BIT(0)
>  #define TBT_ADAPTER(_vdo_)		FIELD_GET(BIT(16), _vdo_)
> -#define   TBT_ADAPTER_LEGACY		0
> -#define   TBT_ADAPTER_TBT3		1
> +#define   TBT_ADAPTER_TBT3		0
> +#define   TBT_ADAPTER_LEGACY		1
>  #define TBT_INTEL_SPECIFIC_B0		BIT(26)
>  #define TBT_VENDOR_SPECIFIC_B0		BIT(30)
>  #define TBT_VENDOR_SPECIFIC_B1		BIT(31)
> 
> ---
> base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb
> change-id: 20250926-topic-tbt_header_bit_fix-17aeb524df4a
> 
> Best regards,
> -- 
> Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

-- 
heikki