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[217.229.29.45]) by smtp.gmail.com with ESMTPSA id p6sm18507003wre.63.2019.02.18.08.28.25 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Feb 2019 08:28:25 -0800 (PST) Date: Mon, 18 Feb 2019 17:28:24 +0100 From: Thierry Reding To: Sowjanya Komatineni Cc: Jonathan Hunter , Timo Alho , "wsa@the-dreams.de" , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-i2c@vger.kernel.org" Subject: Re: [PATCH V1] i2c: tegra: fix tegra186 hw supported features Message-ID: <20190218162824.GA11872@ulmo> References: <1550334787-27703-1-git-send-email-skomatineni@nvidia.com> <20190218084227.GB19363@ulmo> <42aa92c1-309e-88c1-1cd6-07592990730b@nvidia.com> <20190218145002.GC19190@ulmo> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fUYQa+Pmc3FrFX/N" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --fUYQa+Pmc3FrFX/N Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 18, 2019 at 04:13:46PM +0000, Sowjanya Komatineni wrote: > > >=20 > > > On 18/02/2019 08:42, Thierry Reding wrote: > > > > On Sat, Feb 16, 2019 at 08:33:07AM -0800, Sowjanya Komatineni wrote: > > > >> Tegra186 does not support multi-master mode and also there is no= =20 > > > >> master fifo control register. > > > >> > > > >> This patch fixes supported features of Tegra186 and prevents=20 > > > >> crashing during boot as master fifo control register are not=20 > > > >> present on Tegra186 and prior. > > > >> > > > >> Signed-off-by: Sowjanya Komatineni > > > >> --- > > > >> drivers/i2c/busses/i2c-tegra.c | 4 ++-- > > > >> 1 file changed, 2 insertions(+), 2 deletions(-) > > > >=20 > > > > We really should've caught this earlier. Jon, let's think about way= s=20 > > > > to make it easier to catch these things in the future on our test s= ystem. > > >=20 > > > Indeed. This has fixed the boot regression I was seeing over the=20 > > > weekend on -next for Tegra186. However, I am bit confused here,=20 > > > because when I look at the Tegra186 TRM it states that the I2C=20 > > > supports multi-master mode which disagrees with this patch.=20 > > > Furthermore, it seems odd that > > > Tegra210 and Tegra194 would support multi-master mode but Tegra186=20 > > > does not. So is this really correct? > > > > > > I would expect at least the missing master FIFO registers to cause a = crash on Tegra186. The internal architecture specification also says that m= ulti-master is supported. > > > > > > Sowjanya: do you have other documents that suggest we don't support m= ulti-master on Tegra186 specifically? Or is this to work around an issue sp= ecific to Tegra186? > > > > > > As it is this contradicts documentation, so we need to either fix the= commit to remove only master FIFO support or we need to fix the docs to re= flect reality. > > > > > > Thierry >=20 > Thierry/Jonathan, >=20 > Design wise we support but due to known hw bugs we defeatured > multi-master mode. TRM docs also says no multi master support for > T210, T186 and multi-master is supported only on T194. >=20 > T210 also has multi master enabled in driver. We should disable that > also. Okay, I think it makes sense to split this into two patches: 1) remove master FIFO support on Tegra186 because that leads to a crash 2) remove multi-master support on Tegra210 and Tegra186 with a commit message that explains that it was defeatured because of known bugs Thierry --fUYQa+Pmc3FrFX/N Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAlxq3R0ACgkQ3SOs138+ s6FyNg/9FmE505MLO02XvVpembnhWWl72D4/dpuYn65dXmc7Sq8W/RwPq3q4UJp+ bU78qzpjEHbq07W3mfdWRXNKmmWTvFFSdG9a+p7wk3wvZHT64e0oYG6rS69aZbg4 p5xN1jDsbAWAANYpQzaPQWrykme5JN/9C0OkjYZ7c3Ps2TMZ1ug9JASUluceaDHg XHwvWaQZXP1z0Pin1R5OAKEdy5JYwiwHvMwsdbRJVZn1VK8S1efDJUuAdKW6uPvU 9A5Oc0WypwyNq296HDOtAhoTNFI5lJhaHZIUqD6CkAG798YMOoZNYKvfOaxfd0yl EOISEAjXDNKVMSVY9nV9HhzX6MdFj/8QHd0Pd3P2zA9E88JS4t88vV1fPErUBP17 hQxfz9TXn5NMKz+alKeLTZjFW1ZaxgN5JlyA7AWBDEDZAx6JNDghYr6rfMtY6wam 4YWsCMiWZwifUEobIk4XqpZCyzCEEeoRdcnKye3kTbglg2nnYpWRxP5lOTXe4J1s yrDfpUq716JiaFRHtTHuU2s152yGz9r40tWQfAWrAQ9p3eAb3cV9wb/ZLGvFc4Xz hxCoR61PVxJt44Wwj5BzOq9q9uEhHst9H1vF3Nv07e0jnWeqB+1Mfe0tFm/indlq vLhnzSkxMAsOXWCF8e5Vg7HRikUz5l8JlkhW+y0BeF14xoomt1Q= =kqM0 -----END PGP SIGNATURE----- --fUYQa+Pmc3FrFX/N--