Messages in this thread | | | Subject | Re: [PATCH RFC 2/7] mmc: core: devfreq: Add devfreq based clock scaling support | From | Sayali Lokhande <> | Date | Thu, 4 Oct 2018 18:13:21 +0530 |
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Hi Rob,
On 7/20/2018 8:54 PM, Rob Herring wrote: > On Fri, Jul 13, 2018 at 03:22:58PM +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. >> 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. >> >> Signed-off-by: Talel Shenhar <tatias@codeaurora.org> >> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org> >> --- >> .../devicetree/bindings/mmc/sdhci-msm.txt | 10 + >> drivers/mmc/core/core.c | 560 +++++++++++++++++++++ >> 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, 1059 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. > This should be a common binding in which case will just a list of > frequencies be sufficient. [Sayali] : Can you please elaborate more on what do you mean by common binding here ? Like if you are referring to any already available property (by devfreq ?) to pass min-max frequencies ? Any Documentation file to refer ? > > Rob
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