From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01B2BC43461 for ; Thu, 17 Sep 2020 12:04:10 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 56947208DB for ; Thu, 17 Sep 2020 12:04:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56947208DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id BC7542E107; Thu, 17 Sep 2020 12:04:08 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jwoP7ep+09Ba; Thu, 17 Sep 2020 12:04:06 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 43E8820431; Thu, 17 Sep 2020 12:04:06 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 28C2FC0888; Thu, 17 Sep 2020 12:04:06 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id D7102C0859 for ; Thu, 17 Sep 2020 12:04:04 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id C589587520 for ; Thu, 17 Sep 2020 12:04:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id EyT7FB55zC+n for ; Thu, 17 Sep 2020 12:04:03 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [46.235.227.227]) by hemlock.osuosl.org (Postfix) with ESMTPS id C0F0A8751C for ; Thu, 17 Sep 2020 12:04:03 +0000 (UTC) Received: from kevin (unknown [IPv6:2607:fea8:55f:a950::68f4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: alyssa) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id C9FB029AEF5; Thu, 17 Sep 2020 13:03:47 +0100 (BST) Date: Thu, 17 Sep 2020 08:03:37 -0400 From: Alyssa Rosenzweig To: Steven Price Subject: Re: [PATCH 0/3] drm: panfrost: Coherency support Message-ID: <20200917120337.GA1684@kevin> References: <20200916170409.GA2543@kevin> MIME-Version: 1.0 In-Reply-To: Cc: Rob Herring , Tomeu Vizoso , Neil Armstrong , Kevin Hilman , Linux IOMMU , dri-devel , Will Deacon , "open list:ARM/Amlogic Meson..." , Robin Murphy , linux-arm-kernel , Jerome Brunet X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============3415913113789652897==" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" --===============3415913113789652897== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="6TrnltStXW4iwmi0" Content-Disposition: inline --6TrnltStXW4iwmi0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline > The DDK blob has the ability to mark only certain areas of memory as > coherent for performance reasons. For simple things like kmscube I would > expect that it's basically write-only from the CPU and almost all memory the > GPU touches isn't touched by the CPU. I.e. coherency isn't helping and the > coherency traffic is probably expensive. Whether the complexity is worth it > for "real" content I don't know - it may just be silly benchmarks that > benefit. Right, Panfrost userspace specifically assumes GPU reads to be expensive and treats GPU memory as write-only *except* for a few special cases (compute-like workloads, glReadPixels, some blits, etc). The vast majority of the GPU memory - everything used in kmscube - will be write-only to the CPU and fed directly into the display zero-copy (or read by the GPU later as a dmabuf). --6TrnltStXW4iwmi0 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEQ17gm7CvANAdqvY4/v5QWgr1WA0FAl9jUJAACgkQ/v5QWgr1 WA2dWg/+OmkKrIz3I3zxUDFk1aW47mEA/JzLjdkrFq+J1K67FPajUIaqzgLjYq1b wB3a51QSJoN70Aw9O9jrV/GkEbpSf8QWObN4NtZqYcD58fECprh5oXmEfgD0u5gZ 6Gkoijp15utLoOirt2LkEJpYAxrOjfA9n5+WQLn8qQY1QPwO2AjtNxXWlWNhYqvh CQwDQGoO9FiWNSRPZpx1yHEYP/aDMTW8MqwQ8JsQu2G42TS6ErQUC9OMMZjJ/TYS GLKA4ybkdSnlNwQH0h+7g6LX0Y3WGUUn1xxbd4P7OPFZapV+87+cQS8sottqH7tS Rrja9cH4d7/DjKmn1xjT5ftnagxGkzoJ9eYf13DTedymUAQxMGV5TdZhCeUT0HFz 5es9SnkTjOFAQyKZbjiM5t5Sia0eUHLIKUwX6FFKnWxMTtLF4z8XGhizHQrZ8M5I tQW8f7BzInUEGN5H3FV6spp+P5tL7AkdTEGJ4p87EnoyJfTq2mxWAfTxxN9R01FQ 3yDMyx9bUXif0CNnJjAyTN0WJt17twGKuqAnGu5+oLtK6BXuC5wv9yPyQZ5Zvwgv HnXnb+s10WYXgdOHRNebUvFnDYsIZTp8/qFXiAdKaHT/r7aL/UKm2XQqwz48O40W doi8CBItWk7+SxVkj3w5nxnyl9vhu0Md9HkBvGZEH3wfnPGu4/w= =k8jL -----END PGP SIGNATURE----- --6TrnltStXW4iwmi0-- --===============3415913113789652897== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu --===============3415913113789652897==--