linux-kernel - Re: [RFC PATCH 12/22] thunderbolt: Add Display Port CM handshake for Titan Ridge devices

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Date:   Tue, 1 Oct 2019 14:44:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-usb@...r.kernel.org,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Rajmohan Mani <rajmohan.mani@...el.com>,
        Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>,
        Lukas Wunner <lukas@...ner.de>,
        Alan Stern <stern@...land.harvard.edu>,
        Mario.Limonciello@...l.com,
        Anthony Wong <anthony.wong@...onical.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 12/22] thunderbolt: Add Display Port CM handshake for
 Titan Ridge devices

On Tue, Oct 01, 2019 at 02:38:20PM +0300, Mika Westerberg wrote:
> Titan Ridge devices and newer need an additional connection manager
> handshake in order to do proper Display Port tunneling so implement it
> here.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/thunderbolt/tb_regs.h |  3 +++
>  drivers/thunderbolt/tunnel.c  | 44 +++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
> index 3a39490a954b..8d11b4a2d552 100644
> --- a/drivers/thunderbolt/tb_regs.h
> +++ b/drivers/thunderbolt/tb_regs.h
> @@ -252,6 +252,9 @@ struct tb_regs_port_header {
>  #define ADP_DP_CS_3_HDPC			BIT(9)
>  #define DP_LOCAL_CAP				0x04
>  #define DP_REMOTE_CAP				0x05
> +#define DP_STATUS_CTRL				0x06
> +#define DP_STATUS_CTRL_CMHS			BIT(25)
> +#define DP_STATUS_CTRL_UF			BIT(26)
>  
>  /* PCIe adapter registers */
>  #define ADP_PCIE_CS_0				0x00
> diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
> index 3353396e0806..369800110e5e 100644
> --- a/drivers/thunderbolt/tunnel.c
> +++ b/drivers/thunderbolt/tunnel.c
> @@ -6,6 +6,7 @@
>   * Copyright (C) 2019, Intel Corporation
>   */
>  
> +#include <linux/delay.h>
>  #include <linux/slab.h>
>  #include <linux/list.h>
>  
> @@ -242,6 +243,41 @@ struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
>  	return tunnel;
>  }
>  
> +static int tb_dp_cm_handshake(struct tb_port *in, struct tb_port *out)
> +{
> +	int timeout = 10;
> +	u32 val;
> +	int ret;
> +
> +	/* Both ends need to support this */
> +	if (!tb_switch_is_tr(in->sw) || !tb_switch_is_tr(out->sw))
> +		return 0;

So if the ends are both "Titan Ridge", matches your changelog text, but
where is the "and newer" comment being checked here?

thanks,

greg k-h