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[86.30.250.44]) by smtp.googlemail.com with ESMTPSA id r68sm9232066wmr.43.2019.12.20.02.27.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Dec 2019 02:27:22 -0800 (PST) Subject: Re: [alsa-devel] [PATCH v6 02/11] mfd: wcd934x: add support to wcd9340/wcd9341 codec To: Pierre-Louis Bossart , broonie@kernel.org, lee.jones@linaro.org, linus.walleij@linaro.org Cc: robh@kernel.org, alsa-devel@alsa-project.org, bgoswami@codeaurora.org, vinod.koul@linaro.org, devicetree@vger.kernel.org, spapothi@codeaurora.org, linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org References: <20191219103153.14875-1-srinivas.kandagatla@linaro.org> <20191219103153.14875-3-srinivas.kandagatla@linaro.org> <4492b71e-9923-365c-f22c-3766e2d5bae2@linux.intel.com> From: Srinivas Kandagatla Message-ID: <3fa4997f-4409-97f6-ba10-a87013383eb7@linaro.org> Date: Fri, 20 Dec 2019 10:27:21 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <4492b71e-9923-365c-f22c-3766e2d5bae2@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 19/12/2019 20:05, Pierre-Louis Bossart wrote: >>> >> Note these are the child devices of the MFD SLIMBus device. > > Ah ok. I guess the creation of those child devices when the parent > SLIMbus device reports PRESENT initially if fine, it's the part where > you remove them if the device loses sync or gets powered off which is > odd. And I guess technically you could still have race conditions where > a child device starts a transaction just as the parent is no longer > attached to the bus. Losing power to SLIMBus device is very odd usecase and if it happens suggests that threre are bigger issues on the board design itself. This case should never happen. Even if it happens we would get timeout errors on every SLIMbus transactions. > >>> I would however not remove the devices when the status is down but >>> only on an explicit .remove. >> >> Am open for suggestions but I would not like the child devices to talk >> on the bus once the SLIMbus device is down! Only way to ensure or make >> it silent is to remove. > > it's as if you are missing a mechanism to forward the parent status to > the children so use remove() for lack of a better solution? That is true. This gives bit more control on the slave device lifecycle. Current solution works fine for now with less complexities across multiple drivers. I also agree that there is scope of improvement in future for this. Thanks, srini