linux-kernel - Re: [PATCH v4 4/5] platform/chrome: cros_ec_typec: Add Displayport Alternatemode 2.1 Support

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Message-ID: <ZQsE5hgm4qYpr/My@smile.fi.intel.com>
Date:   Wed, 20 Sep 2023 17:42:46 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Utkarsh Patel <utkarsh.h.patel@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        heikki.krogerus@...ux.intel.com, pmalani@...omium.org,
        chrome-platform@...ts.linux.dev, bleung@...omium.org
Subject: Re: [PATCH v4 4/5] platform/chrome: cros_ec_typec: Add Displayport
 Alternatemode 2.1 Support

On Tue, Sep 19, 2023 at 07:32:42PM -0700, Utkarsh Patel wrote:
> Displayport Alternatemode 2.1 requires cable capabilities such as cable
> signalling, cable type, DPAM version which then will be used by mux
> driver for displayport configuration. These capabilities can be derived
> from the Cable VDO.

...

> +	/**

Are you sure?

> +	 * Get cable VDO for thunderbolt cables and cables with DPSID but does not
> +	 * support DPAM2.1.
> +	 */

...

> +	if (cable_dp_vdo & DP_CAP_DPAM_VERSION) {
> +		dp_data.conf |= cable_dp_vdo;
> +	} else if (cable_tbt_vdo) {
> +		dp_data.conf |=  TBT_CABLE_SPEED(cable_tbt_vdo) << DP_CONF_SIGNALLING_SHIFT;
> +
> +		/* Cable Type */
> +		if (cable_tbt_vdo & TBT_CABLE_OPTICAL)
> +			dp_data.conf |= DP_CONF_CABLE_TYPE_OPTICAL << DP_CONF_CABLE_TYPE_SHIFT;
> +		else if (cable_tbt_vdo & TBT_CABLE_RETIMER)
> +			dp_data.conf |= DP_CONF_CABLE_TYPE_RE_TIMER << DP_CONF_CABLE_TYPE_SHIFT;
> +		else if (cable_tbt_vdo & TBT_CABLE_ACTIVE_PASSIVE)
> +			dp_data.conf |= DP_CONF_CABLE_TYPE_RE_DRIVER << DP_CONF_CABLE_TYPE_SHIFT;
> +	} else if (PD_IDH_PTYPE(port->c_identity.id_header) == IDH_PTYPE_PCABLE) {
> +		dp_data.conf |= VDO_TYPEC_CABLE_SPEED(port->c_identity.vdo[0]) <<
> +				DP_CONF_SIGNALLING_SHIFT;
> +	}

You can also make it a bit more readable with (use better names
if you think it's needed)

	u32 signalling = 0;
	u32 cable_type = 0;

	...

	if (cable_dp_vdo & DP_CAP_DPAM_VERSION) {
		dp_data.conf |= cable_dp_vdo;
	} else if (cable_tbt_vdo) {
		signalling = TBT_CABLE_SPEED(cable_tbt_vdo);

		/* Cable Type */
		if (cable_tbt_vdo & TBT_CABLE_OPTICAL)
			cable_type = DP_CONF_CABLE_TYPE_OPTICAL;
		else if (cable_tbt_vdo & TBT_CABLE_RETIMER)
			cable_type = DP_CONF_CABLE_TYPE_RE_TIMER;
		else if (cable_tbt_vdo & TBT_CABLE_ACTIVE_PASSIVE)
			cable_type = DP_CONF_CABLE_TYPE_RE_DRIVER;
	} else if (PD_IDH_PTYPE(port->c_identity.id_header) == IDH_PTYPE_PCABLE) {
		signalling = VDO_TYPEC_CABLE_SPEED(port->c_identity.vdo[0]);
	}

	dp_data.conf |= signalling << DP_CONF_SIGNALLING_SHIFT;
	dp_data.conf |= cable_type << DP_CONF_CABLE_TYPE_SHIFT;

-- 
With Best Regards,
Andy Shevchenko