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[46.91.226.206]) by smtp.gmail.com with ESMTPSA id p21sm2508458wmc.25.2019.10.29.06.37.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Oct 2019 06:37:25 -0700 (PDT) Date: Tue, 29 Oct 2019 14:37:24 +0100 From: Thierry Reding To: Dmitry Osipenko Cc: Jonathan Hunter , Peter De Schrijver , linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 2/2] soc/tegra: pmc: Remove unnecessary memory barrier Message-ID: <20191029133724.GI508460@ulmo> References: <20190926191755.27131-1-digetx@gmail.com> <20190926191755.27131-2-digetx@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BWWlCdgt6QLN7tv3" Content-Disposition: inline In-Reply-To: <20190926191755.27131-2-digetx@gmail.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --BWWlCdgt6QLN7tv3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Sep 26, 2019 at 10:17:55PM +0300, Dmitry Osipenko wrote: > The removed barrier isn't needed because writes/reads are strictly ordered > and even if PMC had separate ports for writes, it wouldn't matter since > the hardware logic takes into effect after triggering CPU's power-gating > and at that point all CPU accesses are guaranteed to be completed. That > barrier was copied from the old arch/ code during transition to the soc/ > PMC driver and even that the code structure was different back then, the > barrier didn't have a real useful purpose from the start. Lastly, the > tegra_pmc_writel() naturally inserts wmb() because it uses writel(), > and thus this change doesn't actually make any difference in terms of > interacting with hardware. Hence let's remove the barrier to clean up > code a tad. >=20 > Signed-off-by: Dmitry Osipenko > --- >=20 > Changelog: >=20 > v5: Extended the commit's message. >=20 > v4: No changes. >=20 > v3: No changes. >=20 > v2: New patch that was added after Jon's Hunter pointing that it's better > not to change the barrier's placement in the code. In fact the barrier > is not needed at all. >=20 > drivers/soc/tegra/pmc.c | 2 -- > 1 file changed, 2 deletions(-) Applied to for-5.5/soc, thanks. 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