This patch series is RFC for support of Dynamic Voltage and Frequency Scaling (DVFS) for OMAP devices. DVFS is a technique that uses the optimal operating frequency and voltage to allow a task to be performed in the required amount of time. OMAP processors have voltage domains whose voltage can be scaled to various levels depending on which the operating frequencies of certain devices belonging to the domain will also need to be scaled. This voltage frequency tuple is known as Operating Performance Point (OPP). A device can have multiple OPP's. Also a voltage domain could be shared between multiple devices. Also there could be dependencies between various voltage domains for maintaining system performance like VDD<X> should be at voltage v1 when VDD<Y> is at voltage v2. The design of this framework take into account all the above mentioned points. To summarize the basic design of DVFS framework:- 1. Have device opp tables for each device whose operating frequency can be scaled. This is easy now due to the existance of hwmod layer which allow storing of device specific info. The device opp tables contain the opp pairs (frequency voltage tuples), the voltage domain pointer to which the device belongs to, the device specific set_rate and get_rate API's which will do the actual scaling of the device frequency and retrieve the current device frequency. 2. Introduce use counting on a per VDD basis. This is to take care multiple requests to scale a VDD. The VDD will be scaled to the maximum of the voltages requested. 3. Keep track of all scalable devices belonging to a particular voltage domain the voltage layer. 4. Generic API in the omap device layer which can be called by anybody to scale a device opp. This API will take in the device pointer and frequency to which the device needs to be scaled to. This API will then internally find out the voltage domain to which the device belongs to and the voltage to which the voltage domain needs to be put to for the device to be scaled to the new frequency from the device opp table. Then this API will call into the newly introduced API in voltage layer (as mentioned in 2) to see if there are other requests for the associated voltage domain to be at a voltage higher than the current chosen one. If not this API will go ahead and scale the voltage domain to the new voltage, run through the list of all scalable devices belonging to this voltage domain and scale them to the appropriate frequencies using the set_rate pointer in the device opp table.s Work pending - 1. Handle inter VDD dependencies. 2. Add OMAP4 support. Contributors to conceptualization of the design include Benoit Cousson <b-cousson@xxxxxx>, Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>, Paul Wamsley <paul@xxxxxxxxx>, Vishwanath Sripathy <vishwanath.bs@xxxxxx> Parthasarathy Basak <p-basak2@xxxxxx> Anand Sawant <sawant@xxxxxx> This patch series is primarily based of pm-sr branch of kevin's PM tree due to it's dependency on the newly introduced opp and voltage layer. On top of this branch I had to apply a few patches to test out dvfs using cpufreq framework. The following are the link to these additional patches. https://patchwork.kernel.org/patch/107876/ http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=commit;h=aa14cb9937e67c48f760c99a3c7fb3b2e7f5e623 http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=commit;h=8f1298921d10789bb2f0a2d56cd3b92d844a1450 http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=commit;h=10474ce3b07949d791b419aad433590e072e7159 http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=commit;h=52fd40b873f8cd5aaea2d01d86ef35017c207eba http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=commit;h=57a2e45ff4a596a175aba27ae55a2b0d99adc3b5 This series has been tested on OMAP3430 SDP for mpu and iva DVFS through cpu freq framework. Thara Gopinath (7): OMAP: Introduce a user list for each voltage domain instance in the voltage driver. OMAP: Introduce API in the OPP layer to find the opp entry corresponding to a voltage. OMAP: Introduce voltage domain pointer and device specific set rate and get rate in device opp structures. OMAP: Voltage layer changes to support DVFS. OMAP: Introduce device set_rate and get_rate. OMAP3: Update OMAP3 opp tables to contain the voltage domain and device set rate get rate info OMAP3: Update cpufreq driver to use the new set_rate API arch/arm/mach-omap2/cpufreq34xx.c | 160 +++++++++++++++++++---- arch/arm/mach-omap2/voltage.c | 172 ++++++++++++++++++++++++- arch/arm/plat-omap/cpu-omap.c | 5 +- arch/arm/plat-omap/include/plat/omap_device.h | 2 + arch/arm/plat-omap/include/plat/opp.h | 39 ++++++- arch/arm/plat-omap/include/plat/voltage.h | 6 +- arch/arm/plat-omap/omap_device.c | 87 +++++++++++++ arch/arm/plat-omap/opp.c | 75 +++++++++-- 8 files changed, 505 insertions(+), 41 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
