From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5DF5439B962 for ; Wed, 29 Apr 2026 09:59:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777456790; cv=none; b=SU6iG1ox5KxjKwPKHPQbTyzQJMxYz5w+Ip1HEOCJcS7vJpXnHZ9YPGkMH9Poi3p8rboTnT3ZQ6+POFQUC4kiowAvPXAQIXWNgxOIvpExbF9ZV63OekPiPxu37HTfembkRnnpXrhRgd/ihCnD+8g5/O/amfu4Ncj0doihZ1mlAXc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777456790; c=relaxed/simple; bh=q6vmAuvAIUD7eWo4i0FbkjdgFQPxmazBd7Ozjn7kw0g=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=jJAKjQhcSZyH8bCknLmtC38MTmrFSeF8iuOIctdibTyMohax3qfG0ETDVaTkWofUKKjn7XgmtrLsAD2AC82cfr+KN452zITvOJfUgpWt1UBqZKbbtlwUvYSlBYL2PZ8or7a/VTN/TjeSh/DnxtSWOHGvVLI6lihXnzyEfFVD/6s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=ggnqVmrt; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="ggnqVmrt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1777456787; bh=q6vmAuvAIUD7eWo4i0FbkjdgFQPxmazBd7Ozjn7kw0g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ggnqVmrtt5BJk9cIuAgE0baPndYQNyXSjHCjI7ZG4tCnk6BfWQJ0qiHJlkVoND4kh IiCp3tKPFIt3ZG6SbxDp2e/oDSrse7Yz0aZDZOBArnO8xaWYaTNXnUGfZwUoE1QI+l m3KwdDTAtYK8R+tPQ9jEn5n+dIkboCzRVK0p7XkHBW5BkbmoIqlIGMKSH/7cMyUp14 FawPsP+prCk7xOzmoXMNjTpGKMoL+fmdQJJhyR7UibVwf1txM1znvdbo4C1mqai9oT rj8tew8l2+3vWFD/Dy9QeF8G+H2AZ1FdgbE8BskjyV/B/as5DwZM6CFeibw7EmUTyy bTgVsSxNZI4MA== Received: from fedora (unknown [100.64.0.11]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 06C0217E061E; Wed, 29 Apr 2026 11:59:46 +0200 (CEST) Date: Wed, 29 Apr 2026 11:59:43 +0200 From: Boris Brezillon To: Steven Price , Liviu Dudau Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Chia-I Wu Subject: Re: [PATCH 00/10] drm/panthor: Reduce dma_fence signalling latency Message-ID: <20260429115943.2e41e104@fedora> In-Reply-To: <20260429-panthor-signal-from-irq-v1-0-4b92ae4142d2@collabora.com> References: <20260429-panthor-signal-from-irq-v1-0-4b92ae4142d2@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit +Chia-I On Wed, 29 Apr 2026 11:38:27 +0200 Boris Brezillon wrote: > Right now, panthor is one of the rare drivers to signal fences > from work items (not even from the threaded IRQ handler). We > could move that to the threaded handler, but that would still > leave the latency caused by the scheduling of the IRQ thread. > > Instead, this patchset moves all the job IRQ processing to > the raw IRQ handler, which is fine because what the current > code does is demux the interrupts and deferring actual handling > to sub work items. The only bits we keep in the IRQ path is > the dma_fence signalling, which should be acceptable, in term > of CPU cycles spent in the IRQ context. > > Pretty much all the patches except the last two are just > preparing the ground to get there. The second to last one > does the thread -> IRQ transition, and the last one is some > experimental interrupt coalescing support that I've added > because I noticed moving job IRQ handling to the raw handler > generates quite a lot of interrupts in some case, and having > the system constantly interrupted like that can be > detrimental. > > Signed-off-by: Boris Brezillon > --- > Boris Brezillon (10): > drm/panthor: Make panthor_irq::state a non-atomic field > drm/panthor: Move the register accessors before the IRQ helpers > drm/panthor: Replace the panthor_irq macro machinery by inline helpers > drm/panthor: Extend the IRQ logic to allow fast/raw IRQ handlers > drm/panthor: Make panthor_fw_{update,toggle}_reqs() callable from IRQ context > drm/panthor: Prepare the scheduler logic for FW events in IRQ context > drm/panthor: Automate CSG IRQ processing at group unbind time > drm/panthor: Automatically enable interrupts in panthor_fw_wait_acks() > drm/panthor: Process FW events in IRQ context > drm/panthor: Introduce interrupt coalescing support for job IRQs > > drivers/gpu/drm/panthor/panthor_device.h | 358 ++++++++++++++--------- > drivers/gpu/drm/panthor/panthor_drv.c | 1 + > drivers/gpu/drm/panthor/panthor_fw.c | 226 +++++++++++++-- > drivers/gpu/drm/panthor/panthor_fw.h | 11 +- > drivers/gpu/drm/panthor/panthor_gpu.c | 27 +- > drivers/gpu/drm/panthor/panthor_mmu.c | 38 +-- > drivers/gpu/drm/panthor/panthor_pwr.c | 21 +- > drivers/gpu/drm/panthor/panthor_sched.c | 475 ++++++++++++++----------------- > 8 files changed, 698 insertions(+), 459 deletions(-) > --- > base-commit: 7455a0583a906533041a80e48c6a2e3230cce96e > change-id: 20260429-panthor-signal-from-irq-d33684f4d292 > prerequisite-message-id: <20260427155934.416502-1-karunika.choo@arm.com> > prerequisite-patch-id: 70905a2eb09ab2b31d242a5ed5af3b42fb6a464c > prerequisite-patch-id: aa4c22669f80328039762f25c0b3942bbadbdc89 > prerequisite-patch-id: 7f61bcee3c4bb5703900b18d5b6e0f52e622f29d > prerequisite-patch-id: 3402f4d60aa526d40113fc3d9b3e599f8f89e705 > prerequisite-patch-id: 00ddbd3d455891f6950609614c1acd2baa78b0db > prerequisite-patch-id: 6a9928f609e3757cadebb2df6795d0da55745f4e > prerequisite-patch-id: fd91f68f25d4bc93eec405f0131f5ae4284bfaf2 > prerequisite-patch-id: 553958a10a0ca2f20f7883ad4c752cfc7485c5a8 > > Best regards,