From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH V1 2/7] mmc: core: devfreq: Add devfreq based clock scaling support Date: Wed, 17 Oct 2018 09:04:52 -0500 Message-ID: <20181017140452.GA7908@bogus> References: <1539003486-24087-1-git-send-email-sayalil@codeaurora.org> <1539003486-24087-3-git-send-email-sayalil@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1539003486-24087-3-git-send-email-sayalil@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Sayali Lokhande Cc: adrian.hunter@intel.com, ulf.hansson@linaro.org, mark.rutland@arm.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, shawn.lin@rock-chips.com, linux-arm-msm@vger.kernel.org, georgi.djakov@linaro.org, devicetree@vger.kernel.org, asutoshd@codeaurora.org, stummala@codeaurora.org, venkatg@codeaurora.org, vviswana@codeaurora.org, bjorn.andersson@linaro.org, riteshh@codeaurora.org, vbadigan@codeaurora.org, dianders@google.com, Talel Shenhar List-Id: devicetree@vger.kernel.org On Mon, Oct 08, 2018 at 06:28:01PM +0530, Sayali Lokhande wrote: > This change adds the use of devfreq to MMC. > Both eMMC and SD card will use it. > For some workloads, such as video playback, it isn't > necessary for these cards to run at high speed. > Running at lower frequency, for example 52MHz, in such > cases can still meet the deadlines for data transfers. > Scaling down the clock frequency dynamically has power > savings not only because the bus is running at lower frequency > but also has an advantage of scaling down the system core > voltage, if supported. Is there really power savings if there's no voltage control? > Provide an ondemand clock scaling support similar to the > cpufreq ondemand governor having two thresholds, > up_threshold and down_threshold to decide whether to > increase the frequency or scale it down respectively. > The sampling interval is in the order of milliseconds. > If sampling interval is too low, frequent switching of > frequencies can lead to high power consumption and if > sampling interval is too high, the clock scaling logic > would take long time to realize that the underlying > hardware (controller and card) is busy and scale up > the clocks. Why the short lines? > > Signed-off-by: Talel Shenhar > Signed-off-by: Sayali Lokhande > --- > .../devicetree/bindings/mmc/sdhci-msm.txt | 10 + Bindings should be separate patches. > drivers/mmc/core/core.c | 556 +++++++++++++++++++++ > drivers/mmc/core/core.h | 7 + > drivers/mmc/core/debugfs.c | 46 ++ > drivers/mmc/core/host.c | 8 + > drivers/mmc/core/mmc.c | 200 +++++++- > drivers/mmc/core/sd.c | 72 ++- > drivers/mmc/host/sdhci-msm.c | 37 ++ > drivers/mmc/host/sdhci-pltfm.c | 11 + > drivers/mmc/host/sdhci.c | 27 + > drivers/mmc/host/sdhci.h | 8 + > include/linux/mmc/card.h | 5 + > include/linux/mmc/host.h | 70 +++ > 13 files changed, 1055 insertions(+), 2 deletions(-) > > diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt > index 502b3b8..bd8470a 100644 > --- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt > +++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt > @@ -26,6 +26,15 @@ Required properties: > "cal" - reference clock for RCLK delay calibration (optional) > "sleep" - sleep clock for RCLK delay calibration (optional) > > +Optional Properties: > +- qcom,devfreq,freq-table - specifies supported frequencies for clock scaling. > + Clock scaling logic shall toggle between these frequencies based > + on card load. In case the defined frequencies are over or below > + the supported card frequencies, they will be overridden > + during card init. In case this entry is not supplied, > + the driver will construct one based on the card > + supported max and min frequencies. > + The frequencies must be ordered from lowest to highest. Why is this qcom specific? I believe I also saw interconnect binding for SD/MMC. How does that relate to this? There should be some coordination of this work. > Example: > > sdhc_1: sdhci@f9824900 { > @@ -43,6 +52,7 @@ Example: > > clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>; > clock-names = "core", "iface"; > + qcom,devfreq,freq-table = <52000000 200000000>; > }; > > sdhc_2: sdhci@f98a4900 {