Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] dmaengine: tegra: fix broken 'select' statement
To:     Arnd Bergmann <arnd@arndb.de>, Vinod Koul <vkoul@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>
Cc:     Dan Williams <dan.j.williams@intel.com>, dmaengine@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org
References: <20200408200504.4067970-1-arnd@arndb.de>
From:   Stephen Warren <swarren@wwwdotorg.org>
Autocrypt: addr=swarren@wwwdotorg.org; prefer-encrypt=mutual; keydata=
 xsFNBE6KoecBEACosznehcVarBMNKGOiQ4MBbDAKQo73RDLP4hKEtaTVoQKg7tAM/tcQgbR6
 p1NSxVq9tunbEskwHkHc/ES/xT+JBFMmG8mh2SmBocyuNjlN8lsW8r2CuLA8EuDr7Laz5yl0
 Gf/G3Q+yYH+ytUnUuPmlxTueR7MNxIT0lz0fjil2HJclha/T3o8osagYWsXyN9Iaqy+6YTit
 fG4hVCr0s+3SYylRp9m2/LaP0CPTQVCJKnv1Oq83PnnV/BA/9sBYxDaVNGfdz2FAWqSH4H7q
 oyonAMzsF7f/cTYcFGTN3kL3UonG43DHpqCv+gHMKITBCxN+3HjX4wuNC7raoHVRRbx7/JES
 ZrJ1ymKdMNxl8bquldTk6VyAJlTRjuq7jRY9LIEHcns91MYFgpz7RAhCPmXnsMgpuIvU/yTE
 aApIAkHSo2Nyk9NeyIsji5voa9VAAoZKLGFTkhyPLEcjU9JmH/x224zGLtK28bL+P61PCk02
 jG7RTF4665IDbmC8UNvEm9mBgFNlEgOPqbVF9oa5Gd9cnaOTucDLJqjCpM53SM5Jd3eRHk7A
 zDHSBWsRsmKXU4hhxlu+90tb7I0TcjPfqeCrO46rNELdskcJAlLzx0v07+IhhGAM70oAbP49
 VBA7hsVCimuITFSUUwAtzFJmFg/mjxNdftTr3yssaK41VmxsIQARAQABzSZTdGVwaGVuIFdh
 cnJlbiA8c3dhcnJlbkB3d3dkb3Rvcmcub3JnPsLBrAQTAQIAPwIbAwYLCQgHAwIGFQgCCQoL
 BBYCAwECHgECF4AWIQTmd6/Z3M3mpZiMqw6bjacJJlQhnAUCXboEKAUJERCVvgAhCRCbjacJ
 JlQhnBYhBOZ3r9nczealmIyrDpuNpwkmVCGc074P/jq2nW6yORiLCgiTX3I0ro0sUq6aOvkq
 WH/g1Oq4fTr6TmabZVFvuuUZDF/AwB6p0Mm6tWar29nF1/OEx7QrrrHrBEcaAEHmZFjoenDK
 3SJDHDLBkcuMiZS7CFdb22vBYrgzoHwptySrRcHWW5rxhAKgyTX/p7F96zicNPS1sljc7JNW
 oik6b90PmCeKCeuoH4ruBO+3naDInKrL389xvujF38aTkgai9DJtWjWizZzAP+DWJrHtb6zz
 fsPA41hnZ5mKmUbiuJehPbv0+Q6QSFjLhNiP6lvkV34uANH3TQn2o6nApoa3XT5fIxrJOFrz
 q6xuM2tcyd/dRr1TdtIQCRABaKYIF/mgtMa19+GbLI8A/t1RmxEhlctSEUOFO7E3PNiwIjvI
 OpqZjq3NR8/+Lw2Zv9H3B7Wywk87ESwaYhYL29AzVvAMKFYHpDbn0abN+GVyit+fVbrUvKed
 nr63H7bG81O1DBA44gBDaIZhwOQDqeTou05rFa2PLGbdd6YL8AM6nWVI9UqD2+aKg1GcXtFO
 cq3Ll5fzUoSys13a14cCDLI82XvPxJh8TOtC8wJywYwAa75ieuVXxWh74d9qRYq3iJZpIWCE
 s5NkkGN4Q1dul84OQrwiN+2PYH+k2M6MGMt+9MHEoR+vrtMNUIeCa/ctYX6mb+nSPZAr5Fx0
 LZMdzsFNBE6KoecBEAC5xnYhQJCsaOCCTrzpnifMCUC0zLvhKgdChd4QAJm8ap+qufkbz3oF
 iJx1u19AbX8PNT3mdtwsguJhcamdT49YepVEvo6znc4S/pxjbX882CovKoOqSPSnE9VIbLHG
 VnxwDQGp2cbdqYOF7qvr4wGliR/X1Hx72EK3kSppvGEQp/uyW0QzHUC6XX9TdKawWAPohaqm
 TXqaQSMp6uOhNCTmydTAN2V4bJpQBU3BpNNtBZ+mnHlu/Yl74x0tgIYBqxEVdYz3Ryn1FTTC
 NCKcGiO8px2e7VBsKAiC9tRMZYjuH5HaS0SgI2asbAqX1OduiC1BTvM9P3oqps0Vs8zR7nxt
 Lodws79Vjoc0Ab/5BSEMIooww0Eo/VYwqnMs6Bvk5dtv7kCVRMUyV2JrTD0cCw0E+urjW5Dw
 kr4hRDTi8Xr45WecHxXMHZOllE4q8PxaK+rwoX0boXIQ+i3bL6Nemj3d6+ELYe5Dpswzmn0Z
 RrDegq7ly9303bEve09cIVZ4PS2rkx54bGN9R9TgXhU7XnRHyCSKFE8vSXXyG9Lu2aHq+od1
 bUoTOQfoLOAeJOrbo+crZAq33W69t6rD0Q1WHuvzd2zpOQdlsrUOGkDKuk0dBxpzlf8uusaD
 lE5fjd4RQXreKVjSKczrMd9uhLe2cdsVNFljHZlXnFRciNsUge6AKwARAQABwsGTBBgBAgAm
 AhsMFiEE5nev2dzN5qWYjKsOm42nCSZUIZwFAl03xTwFCRD+ZlUAIQkQm42nCSZUIZwWIQTm
 d6/Z3M3mpZiMqw6bjacJJlQhnA+lD/9/DbFI8lUQyb0ZOBLHW6iX+Ps++hElYOmjL4T4f6wa
 FMNiFk2lPom/xq8OL5B2swWC7w5o/j+GwrS6MbkL/s932zQ15+AVD0HfhTBKKQEnQUPVLM2T
 9AcXpY0s8AYsWa89YNTJpdbFc5ep/Nx6R3rYu0ixJtrJT+p19qhIavMRaHMYuxGLO4xs4CUO
 Z2kq6+KKNIAi63FjYBLYPPGd6KyXSj1zWZwAE6qLLPl/MGrbKSqETj01Z7NuGYbJNVi0ooIq
 b+iBGsPQRx6FhiVXbo9eheBJ/Qui4QVCur2WFzxzlhqTDknA0d5by+tQvg4NUmm0u64YIeGQ
 5U4wLL60kch1Cr1MSM9eBi1fsq3FRCd7QQnCO3MaJ9odE5BaHKpDFzd9cxrBA/StoDkiU6Ci
 o9HrHblS9gNQemZT+WTSA/t7dB97NesqGbDtdW5G0wfliNFmvS9qDpUe3hSa6f9PgCz/8QzS
 aXcBhnI7xRoXZxRKo3mnNihC/5hnNxMsUP5oNdhRPVyTs8wlLKXBHXUpj6OgoFO01e05Niak
 UR3Mub2hXCUcJ3UuO1+nxY88x+K86LZnMCa+0A6RTeTJAz6aaF2Fr/h7xncLk3LG3/ODQFjb
 S1cWYsAeg++INJffJzend+91hvGp1WcI8TGc6BjYnO5mKBuVumOKXi4wa2OJo9y3lMLBkwQY
 AQIAJgIbDBYhBOZ3r9nczealmIyrDpuNpwkmVCGcBQJdugQxBQkREJXIACEJEJuNpwkmVCGc
 FiEE5nev2dzN5qWYjKsOm42nCSZUIZywWA//d3PsJki5IAkAsALeF+qMHtyGFCf/vc1V91jN
 MC2wuAo7MKLxQDyMdkjSp0s+UrDzTY9bYocfB2G3mXnJDEzQSd6snf0pEMQVf77SGbddcFCO
 GsfJuE6DmsSjVncK3JO9/eXeqyTup/PNN2RYkuR394+RxeUvf/f1km80DtO0beI3g/EtMSE1
 ljLwDuh98j9qVSJ0xK7cmf/ngi703BltS8rpoXDioS1fTlVFdJpGOH94PVlyJsDbHy4rDeFU
 Ptk1Q0hRGKNpCPCVQntLAc3mH9++3oVxxCsvgUfjHbgwzptTGj6SbXH3piyBPMHRXhtIiHRH
 kkrxbMKGuzkU5dPmMv7Mzw9yaMYY8mmPZMPJoLA0bW6DuZ1nAz9U7njM/xb1WIZHKA8HVfTz
 4fO8lP7jxCod6uBvu3vgBRbYTu3QoQjxhIjbAE5P9ZxLggx919dKypYiXeIPB8OHg5/4LwEi
 f+rjKF/HHMo+ZCJx9BCZeW5yNkeTm638JfD1XjrZzDNsawdMFFdGL5TJrubu52fxsml41ay6
 Qacni4jVUmZDP1HVYzcQN42O7ynZKMecpwM3G6V9L3Ifs8VpfdPpOnJb6TOXUOrITz4kyHDy
 0hRsU1DwGeqzyyZAJT6MHZR0qO93XKFy9+WgzUXS2j0rQ9D4zTQI4c0Zp3ri8v5ZDXJh1W0=
Message-ID: <7c637edc-200b-ed8e-26c8-52c2c7d8025a@wwwdotorg.org>
Date:   Wed, 8 Apr 2020 15:37:34 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.4.1
MIME-Version: 1.0
In-Reply-To: <20200408200504.4067970-1-arnd@arndb.de>
Content-Type: text/plain; charset=utf-8
Content-Language: en-GB
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 4/8/20 2:04 PM, Arnd Bergmann wrote:
> A SoC driver selects the dmaengine driver for the platform it
> is made for, leading to Kconfig warnings in some configurations:
> 
> WARNING: unmet direct dependencies detected for TEGRA20_APB_DMA
>   Depends on [n]: DMADEVICES [=n] && (ARCH_TEGRA [=y] || COMPILE_TEST [=y])
>   Selected by [y]:
>   - SOC_TEGRA_FUSE [=y] && ARCH_TEGRA [=y] && ARCH_TEGRA_2x_SOC [=y]
> 
> WARNING: unmet direct dependencies detected for TEGRA20_APB_DMA
>   Depends on [n]: DMADEVICES [=n] && (ARCH_TEGRA [=y] || COMPILE_TEST [=y])
>   Selected by [y]:
>   - SOC_TEGRA_FUSE [=y] && ARCH_TEGRA [=y] && ARCH_TEGRA_2x_SOC [=y]
> 
> Generally, no driver should 'select' a driver from a different subsystem,
> especially when there is no build-time dependency between the two.

IIRC there's a run-time dependency between the two though; without the
DMA driver available to implement a HW WAR, the fuse driver has to
access fuse registers directly which IIRC can cause a lock-up, or
something like that. So I think allowing APD_DMA to be deselected by the
user is wrong for T20 at least; it simply must be enabled. Perhaps
ARCH_TEGRA_2x_SOC should select it instead?