linux-kernel - Re: [PATCH] platform/chrome: cros_ec_typec: Set Pin Assignment E in DP PORT VDO

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Message-ID: <CANFp7mWQPy2z1dWtHSw1uzMnUCcRJfaqJvGayyjmEvVjnM3KXQ@mail.gmail.com>
Date: Mon, 28 Apr 2025 09:24:08 -0700
From: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
To: Benson Leung <bleung@...omium.org>
Cc: jthies@...gle.com, akuchynski@...omium.org, tzungbi@...nel.org, 
	chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	sukoo@...gle.com, bleung@...gle.com
Subject: Re: [PATCH] platform/chrome: cros_ec_typec: Set Pin Assignment E in
 DP PORT VDO

On Fri, Apr 25, 2025 at 7:48 PM Benson Leung <bleung@...omium.org> wrote:
>
> Pin C and D are used on C-to-C cable applications including docks,
> and for USB-C adapters that convert from DP over USB-C to other
> video standards.
>
> Pin Assignment E is intended to be used with adapter from USB-C to DP
> plugs or receptacles.
>
> All Chromebook USB-C DFPs support DisplayPort Alternate Mode as the DP
> Source with support for all 3 pin assignments. Pin Assignment E is required
> in order to support if the user attaches a Pin E C-to-DP cable.
>
> Without this, the displayport.c alt mode driver will error out of
> dp_altmode_probe with an -ENODEV, as it cannot find a compatible matching
> pin assignment between the DFP_D and UFP_D.
>
> Signed-off-by: Benson Leung <bleung@...omium.org>
> ---
>  drivers/platform/chrome/cros_ec_typec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index d2228720991f..7678e3d05fd3 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -22,8 +22,10 @@
>
>  #define DRV_NAME "cros-ec-typec"
>
> -#define DP_PORT_VDO    (DP_CONF_SET_PIN_ASSIGN(BIT(DP_PIN_ASSIGN_C) | BIT(DP_PIN_ASSIGN_D)) | \
> -                               DP_CAP_DFP_D | DP_CAP_RECEPTACLE)
> +#define DP_PORT_VDO    (DP_CAP_DFP_D | DP_CAP_RECEPTACLE | \
> +                        DP_CONF_SET_PIN_ASSIGN(BIT(DP_PIN_ASSIGN_C) | \
> +                                               BIT(DP_PIN_ASSIGN_D) | \
> +                                               BIT(DP_PIN_ASSIGN_E)))
>
>  static void cros_typec_role_switch_quirk(struct fwnode_handle *fwnode)
>  {
> --
> 2.49.0.850.g28803427d3-goog
>

Please add a Fixes: dbb3fc0ffa95788e00e50ffc6501eb0085d48231

Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>