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[142.162.113.129]) by smtp.gmail.com with ESMTPSA id l26sm974766qkj.38.2021.10.04.09.51.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Oct 2021 09:51:28 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1mXRBX-00AXAU-Qu; Mon, 04 Oct 2021 13:51:27 -0300 Date: Mon, 4 Oct 2021 13:51:27 -0300 From: Jason Gunthorpe To: Florian Fainelli Cc: Mark Brown , Lino Sanfilippo , rjui@broadcom.com, sbranden@broadcom.com, bcm-kernel-feedback-list@broadcom.com, nsaenz@kernel.org, linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, p.rosenberger@kunbus.com, linux-integrity@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] spi: bcm2835: do not unregister controller in shutdown handler Message-ID: <20211004165127.GZ3544071@ziepe.ca> References: <20210928195657.5573-1-LinoSanfilippo@gmx.de> <20211001175422.GA53652@sirena.org.uk> <2c4d7115-7a02-f79e-c91b-3c2dd54051b2@gmx.de> <20211004131756.GW3544071@ziepe.ca> <20211004154436.GY3544071@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Mon, Oct 04, 2021 at 09:36:37AM -0700, Florian Fainelli wrote: > No please don't, I should have arguably justified the reasons why > better, but the main reason is that one of the platforms on which this > driver is used has received extensive power management analysis and > changes, and shutting down every bit of hardware, including something as > small as a SPI controller, and its clock (and its PLL) helped meet > stringent power targets. Huh? for device shutdown? What would this matter if the next step is reboot or power off? > TBH, I still wonder why we have .shutdown() and we simply don't use > .remove() which would reduce the amount of work that people have to do > validate that the hardware is put in a low power state and would also > reduce the amount of burden on the various subsystems. The difference between remove and shutdown really is that 'emergency' sense that shutdown is something that must complete in bounded time and thus only has to concern itself with quieting hardware to a safe state for the next step in the shutdown/reboot/kexec/kdump sequence. Many remove handlers happily block until, eg all user files are closed or something to allow a graceful module unload. Jason