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 E1063CDB46E for ; Thu, 12 Oct 2023 14:37:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343598AbjJLOhB (ORCPT ); Thu, 12 Oct 2023 10:37:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233260AbjJLOg6 (ORCPT ); Thu, 12 Oct 2023 10:36:58 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9619DC0 for ; Thu, 12 Oct 2023 07:36:57 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81DA8C433C7; Thu, 12 Oct 2023 14:36:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697121417; bh=tqPqmHok1AyU/GG626kkM4PFGH7XQeQEOYooofFbE+Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BMAjov1X2fVRTyegaWW28iHtNCwbmTe1ER+CCckjzVHEl8moiISR5Ys0Ad3QBESNC XCzNCnYLVTCqKSaKM+X5dbQ2oQl+p2lhzVyGRJsx9HwFVTyNZp6hYbj2fa7b8H5Sy/ 3n81yeRGgGcmV45bY/mg97c7o6NNjMa/NIXvkR4apDIyYaVJ+nwDo/YyMLqmrx8Wil nssBNW5fPPVUqURzE76CFjUp/JAzjV5vThzwy8HIRpmt8FpQ3euJxC1qiF9Qrwl8iI THEa9ERLSlWS/JtSVovdCGce8bL3D1XBQ35AbEWpKtQJsSEbs4nHjn1kZTBV1jil2W SLIyA23D6wRCA== Date: Thu, 12 Oct 2023 15:36:53 +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 v3 1/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO Message-ID: <20231012-pranker-usage-09a85a36356f@spud> References: <20231012141456.4078-1-jszhang@kernel.org> <20231012141456.4078-2-jszhang@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="tLH7qnMb79tGa+m2" Content-Disposition: inline In-Reply-To: <20231012141456.4078-2-jszhang@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --tLH7qnMb79tGa+m2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Oct 12, 2023 at 10:14:55PM +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 =46rom v2: Reviewed-by: Conor Dooley Thanks, Conor. --tLH7qnMb79tGa+m2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZSgEhQAKCRB4tDGHoIJi 0oQqAP9E3GPMvuDoXMFDfJdL0fEkQ1D91Q115ThR1vWUqlcKCwEAmZexxPc2Ytz3 XSpUhcOVF4jxrEhP3FjNPNvYpXJp6wg= =NXCq -----END PGP SIGNATURE----- --tLH7qnMb79tGa+m2--