From: sashiko-bot@kernel.org
To: "Diego Noguês" <diego.sure@gmail.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: [PATCH RFC] drm/dp_tunnel: Allow BWA when the DP IN adapter does not advertise it
Date: Sat, 31 Oct 2026 00:22:01 +0000 [thread overview]
Message-ID: <sashiko-outbox-191672@kernel.org> (raw)
In-Reply-To: <20261031-dp-tunnel-bwa-flag-v1-1-f94ed3179349@gmail.com>
> From: Diego Noguês <diego.sure@gmail.com>
>
> On an Alder Lake host (i7-1265U) with a Thunderbolt 4 dock (Dell WD22TB4,
> Goshen Ridge) driving two 4K@60 monitors through two DP tunnels, the
> monitor whose tunnel is created second is limited to 4K@30. Which monitor
> is affected depends only on the order in which they are powered on.
>
> The thunderbolt driver enables the BW allocation mode (BWA) on both DP IN
> adapters: it sets the CM BWA support (DP_USB4_DRIVER_BW_CAPABILITY), a
> group ID and the estimated BW. The DP IN adapter, however, never sets
> DP_IN_BW_ALLOCATION_MODE_SUPPORT in DP_TUNNELING_CAPABILITIES (0xe000d
> reads 0x01), so tunnel_regs_are_valid() rejects the tunnel with:
>
> DPTUN: A non-zero group ID is only allowed with BWA support
>
> [ ... ]
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/17742
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Mika Westerberg <westeri@kernel.org>
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Diego Noguês <diego.sure@gmail.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261031-dp-tunnel-bwa-flag-v1-1-f94ed3179349@gmail.com?part=1
prev parent reply other threads:[~2026-10-31 0:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-31 0:18 [PATCH RFC] drm/dp_tunnel: Allow BWA when the DP IN adapter does not advertise it Diego Noguês via B4 Relay
2026-10-31 0:18 ` Diego Noguês
2026-10-31 0:22 ` sashiko-bot [this message]
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