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[94.29.46.111]) by smtp.googlemail.com with ESMTPSA id w10sm1488552lfn.308.2021.12.13.08.44.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Dec 2021 08:44:49 -0800 (PST) Subject: Re: [PATCH 06/25] ARM: tegra: Fix compatible string for Tegra30+ timer To: Thierry Reding Cc: Jon Hunter , linux-tegra@vger.kernel.org References: <20211209173356.618460-1-thierry.reding@gmail.com> <20211209173356.618460-7-thierry.reding@gmail.com> <8988f759-689f-7c46-ba1e-3eab1a91de7c@gmail.com> From: Dmitry Osipenko Message-ID: <0be69e6b-bec4-faf9-ce1a-ce513a217622@gmail.com> Date: Mon, 13 Dec 2021 19:44:48 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org 13.12.2021 19:04, Thierry Reding пишет: > On Fri, Dec 10, 2021 at 06:23:34PM +0300, Dmitry Osipenko wrote: >> 10.12.2021 16:42, Thierry Reding пишет: >>> On Thu, Dec 09, 2021 at 10:36:43PM +0300, Dmitry Osipenko wrote: >>>> 09.12.2021 20:33, Thierry Reding пишет: >>>>> From: Thierry Reding >>>>> >>>>> The TKE (time-keeping engine) found on Tegra30 and later is not >>>>> backwards compatible with the version found on Tegra20, so update the >>>>> compatible string list accordingly. >>>>> >>>>> Signed-off-by: Thierry Reding >>>>> --- >>>>> arch/arm/boot/dts/tegra114.dtsi | 2 +- >>>>> arch/arm/boot/dts/tegra124.dtsi | 2 +- >>>>> arch/arm/boot/dts/tegra30.dtsi | 2 +- >>>>> 3 files changed, 3 insertions(+), 3 deletions(-) >> ... >>>>> timer@60005000 { >>>>> - compatible = "nvidia,tegra30-timer", "nvidia,tegra20-timer"; >>>>> + compatible = "nvidia,tegra30-timer"; >>>>> reg = <0x60005000 0x400>; >>>>> interrupts = , >>>>> , >>>>> >>>> >>>> What exactly is incompatible? IIRC, T30+ is a superset of T20. This >>>> patch should be wrong, also see [1]. >>> >>> As the comment in that location explains, Tegra114 and later have an >>> architectural timer that is preferred over the legacy timer. So while >>> this doesn't technically make Tegra114 incompatible (in terms of >>> register programming, etc.) with Tegra20, in practice we don't want >>> Tegra20 behaviour on Tegra114 and later. >> >> So the T114 timer code works using the T20 code and we prefer to use the >> ARCH timer on T114+ in the driver, what is the problem then? Where is >> the incompatibility? > > It's the priority that's set differently for Tegra20 and Tegra30. On > Tegra114 and later, the Tegra timer has lower priority so that the > architected timer takes precedence. It's not exactly an > incompatibilitity, but there's no good way to describe it otherwise. Priority is a property of the Linux kernel driver, it's not a hardware property. This whole patch is incorrect and should be dropped, IMO.