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 16:30:16 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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 02:44:09PM +0200, Greg Kroah-Hartman wrote:
> 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?

By "and newer" I mean USB4 devices which are added in patch 17/22. I can
update the changelog here to mention just Titan Ridge, though.