linux-kernel - Re: [PATCH 1/8] usb: typec: Correct the bit values for the Thunderbolt rounded/non-rounded cable support

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Message-ID: <20201110121824.GK1224435@kuha.fi.intel.com>
Date:   Tue, 10 Nov 2020 14:18:24 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Utkarsh Patel <utkarsh.h.patel@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        pmalani@...omium.org, enric.balletbo@...labora.com,
        rajmohan.mani@...el.com, azhar.shaikh@...el.com
Subject: Re: [PATCH 1/8] usb: typec: Correct the bit values for the
 Thunderbolt rounded/non-rounded cable support

On Mon, Nov 09, 2020 at 04:37:09PM -0800, Utkarsh Patel wrote:
> Rounded and non-rounded Thunderbolt cables are represented by two bits as
> per USB Type-C Connector specification v2.0 section F.2.6.
> Corrected that in the Thunderbolt 3 cable discover mode VDO.
> 
> Fixes: ca469c292edc ("usb: typec: Add definitions for Thunderbolt 3 Alternate Mode")

Hold on... Why is this tagged as a fix? What is it fixing?

Why do we even need this change? The field may have two bits, but
only one is used: "10b...11b = Reserved".

> Signed-off-by: Utkarsh Patel <utkarsh.h.patel@...el.com>
> ---
>  include/linux/usb/typec_tbt.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
> index 47c2d501ddce..aad648d14bb3 100644
> --- a/include/linux/usb/typec_tbt.h
> +++ b/include/linux/usb/typec_tbt.h
> @@ -40,11 +40,16 @@ struct typec_thunderbolt_data {
>  #define   TBT_CABLE_USB3_PASSIVE	2
>  #define   TBT_CABLE_10_AND_20GBPS	3
>  #define TBT_CABLE_ROUNDED		BIT(19)
> +#define TBT_CABLE_ROUNDED_SUPPORT(_vdo_) \
> +					(((_vdo_) & GENMASK(20, 19)) >> 19)
> +#define   TBT_GEN3_NON_ROUNDED                 0
> +#define   TBT_GEN3_GEN4_ROUNDED_NON_ROUNDED    1
>  #define TBT_CABLE_OPTICAL		BIT(21)
>  #define TBT_CABLE_RETIMER		BIT(22)
>  #define TBT_CABLE_LINK_TRAINING		BIT(23)
>  
>  #define TBT_SET_CABLE_SPEED(_s_)	(((_s_) & GENMASK(2, 0)) << 16)
> +#define TBT_SET_CABLE_ROUNDED(_g_)	(((_g_) & GENMASK(1, 0)) << 19)
>  
>  /* TBT3 Device Enter Mode VDO bits */
>  #define TBT_ENTER_MODE_CABLE_SPEED(s)	TBT_SET_CABLE_SPEED(s)

thanks,

-- 
heikki