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[99.44.17.11]) by smtp.gmail.com with ESMTPSA id r11sm742619pgl.34.2021.06.09.16.59.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jun 2021 16:59:03 -0700 (PDT) Subject: Re: [PATCH 2/2] mmc: sdhci-iproc: Add support for the legacy sdhci controller on the BCM7211 To: Ulf Hansson , Florian Fainelli Cc: Al Cooper , Linux Kernel Mailing List , Adrian Hunter , BCM Kernel Feedback , DTML , Linux ARM , linux-mmc , Nicolas Saenz Julienne , Ray Jui , Rob Herring , Scott Branden References: <20210602192758.38735-1-alcooperx@gmail.com> <20210602192758.38735-2-alcooperx@gmail.com> From: Florian Fainelli Message-ID: <6acd480a-8928-89bb-0f40-d278294973a1@gmail.com> Date: Wed, 9 Jun 2021 16:59:00 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/9/2021 2:22 AM, Ulf Hansson wrote: > On Wed, 9 Jun 2021 at 05:07, Florian Fainelli wrote: >> >> >> >> On 6/8/2021 5:40 AM, Ulf Hansson wrote: >>> On Wed, 2 Jun 2021 at 21:28, Al Cooper wrote: >>>> >>>> Add support for the legacy Arasan sdhci controller on the BCM7211 and >>>> related SoC's. This includes adding a .shutdown callback to increase >>>> the power savings during S5. >>> >>> Please split this into two separate changes. >>> >>> May I also ask about the ->shutdown() callback and in relation to S5. >>> What makes the ->shutdown callback only being invoked for S5? >> >> It is not only called for S5 (entered via poweroff on a prompt) but also >> during kexec or reboot. The poweroff path is via: >> >> kernel_power_off() -> kernel_shutdown_prepare() -> device_shutdown() -> >> .shutdown() >> >> For kexec or reboot we do not really care about power savings since we >> are about to load a new image anyway, however for S5/poweroff we do care >> about quiescing the eMMC controller in a way that its clocks and the >> eMMC device can be put into low power mode since we will stay in that >> mode for seconds/hours/days until someone presses a button on their >> remote (or other wake-up sources). > > Hmm, I am not sure I understand correctly. At shutdown we don't care > about wake-up sources from the kernel point of view, instead we treat > everything as if it will be powered off. The same .shutdown() path is used whether you kexec, reboot or poweroff, but for poweroff we do care about allowing specific wake-up sources configured as such to wake-up the system at a later time, like GPIOs, RTC, etc. > > We put devices into low power state at system suspend and potentially > also during some of the hibernation phases. > > Graceful shutdown of the eMMC is also managed by the mmc core. AFAICT that calls mmc_blk_shutdown() but that is pretty much it, the SDHCI platform_driver still needs to do something in order to conserve power including disabling host->clk, otherwise we would not have done that for sdhci-brcmstb.c. -- Florian