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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DFF0E784AF for ; Mon, 2 Oct 2023 10:55:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236552AbjJBKzk (ORCPT ); Mon, 2 Oct 2023 06:55:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236192AbjJBKzi (ORCPT ); Mon, 2 Oct 2023 06:55:38 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F390B3 for ; Mon, 2 Oct 2023 03:55:36 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA2DBC433C8; Mon, 2 Oct 2023 10:55:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696244135; bh=F5fHvFLRPSXGAJr5Hur9dBSrn1AlR9jGY19xXDVZ+To=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ebkPo+WRr0ngMFnObD+G/SsGSqtuAZEKlpHHoqkawi7RHXBd0sxsUG1QkXKc4cspE yXV9hVW556TzPBMhNay2gmLR0xCSP7cTqvz24ZSxXFPJHxS7EbVrLlkbu5tPn/va28 KiRrn96lV6TFqopL8izAFIlDB1GsqBvOqDGZbicqpaER2bm9y9z60L/vIcN48UqDMr ldNgeV+OVuCnO8knQ+oMMYiDA8FCXzE1s/WQCoYF6JqHlaCnS6Q9U7ae2hcazzxqQP 7HD6J9uiy4kr71HI+xrd4V1XoE+8q8CmsuaLjEAQr3KbLmBTmTaQA+bP9OVyYNXc5U 3E2ep5dWxtknw== Date: Mon, 2 Oct 2023 11:55:31 +0100 From: Conor Dooley To: Jisheng Zhang Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Emil Renner Berthing Subject: Re: [PATCH v2 1/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO Message-ID: <20231002-angles-utopia-6c6c7b18231e@spud> References: <20231001103433.3187-1-jszhang@kernel.org> <20231001103433.3187-2-jszhang@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="U/Lf1c64QYsza03U" Content-Disposition: inline In-Reply-To: <20231001103433.3187-2-jszhang@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --U/Lf1c64QYsza03U Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Oct 01, 2023 at 06:34:32PM +0800, Jisheng Zhang wrote: > Previously, we use alternative mechanism to dynamically patch > the CMO operations for THEAD C906/C910 during boot for performance > reason. But as pointed out by Arnd, "there is already a significant > cost in accessing the invalidated cache lines afterwards, which is > likely going to be much higher than the cost of an indirect branch". > And indeed, there's no performance difference with GMAC and EMMC per > my test on Sipeed Lichee Pi 4A board. >=20 > Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify > the alternative code, and to acchieve Arnd's goal -- "I think > moving the THEAD ops at the same level as all nonstandard operations > makes sense, but I'd still leave CMO as an explicit fast path that > avoids the indirect branch. This seems like the right thing to do both > for readability and for platforms on which the indirect branch has a > noticeable overhead." >=20 > Signed-off-by: Jisheng Zhang > Tested-by: Emil Renner Berthing Reviewed-by: Conor Dooley Thanks, Conor. --U/Lf1c64QYsza03U Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZRqhowAKCRB4tDGHoIJi 0piXAP9YVt+cUOHo4WTwqUZ7/v9f9zmKv0aMbkueUtWc8W5O7QD/RBTXAJXMS6mi pEEyPYGX00rO85GTDF1mlRpvqiiPKAA= =KGQg -----END PGP SIGNATURE----- --U/Lf1c64QYsza03U--