From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: [PATCH v9 07/20] PM / devfreq: exynos: Update documentation for bus devices using passive governor Date: Tue, 12 Apr 2016 17:19:53 +0900 Message-ID: <570CAFA9.2060607@samsung.com> References: <1460347078-15175-1-git-send-email-cw00.choi@samsung.com> <1460347078-15175-8-git-send-email-cw00.choi@samsung.com> <570CA50A.3010505@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-reply-to: <570CA50A.3010505@samsung.com> Sender: linux-samsung-soc-owner@vger.kernel.org To: Krzysztof Kozlowski , myungjoo.ham@samsung.com, kyungmin.park@samsung.com, kgene@kernel.org, s.nawrocki@samsung.com, tomasz.figa@gmail.com Cc: rjw@rjwysocki.net, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, linux@arm.linux.org.uk, linux.amoon@gmail.com, m.reichl@fivetechno.de, tjakobi@math.uni-bielefeld.de, inki.dae@samsung.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org On 2016=EB=85=84 04=EC=9B=94 12=EC=9D=BC 16:34, Krzysztof Kozlowski wro= te: > On 04/11/2016 05:57 AM, Chanwoo Choi wrote: >> This patch updates the documentation for passive bus devices and add= s the >> detailed example of Exynos3250. >> >> Signed-off-by: Chanwoo Choi >> Acked-by: MyungJoo Ham >> --- >> .../devicetree/bindings/devfreq/exynos-bus.txt | 250 ++++++++++= ++++++++++- >> 1 file changed, 247 insertions(+), 3 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.tx= t b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> index 78171b918e3f..03f13d38f1a1 100644 >> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> @@ -8,22 +8,46 @@ of the bus in runtime. To monitor the usage of eac= h bus in runtime, >> the driver uses the PPMU (Platform Performance Monitoring Unit), wh= ich >> is able to measure the current load of sub-blocks. >> =20 >> +The Exynos SoC includes the various sub-blocks which have the each = AXI bus. >> +The each AXI bus has the owned source clock but, has not the only o= wned >> +power line. The power line might be shared among one more sub-block= s. >> +So, we can divide into two type of device as the role of each sub-b= lock. >> +There are two type of bus devices as following: >> +- parent bus device >> +- passive bus device >> + >> +Basically, parent and passive bus device share the same power line. >> +The parent bus device can only change the voltage of shared power l= ine >> +and the rest bus devices (passive bus device) depend on the decisio= n of >> +the parent bus device. If there are three blocks which share the VD= D_xxx >> +power line, Only one block should be parent device and then the res= t blocks >> +should depend on the parent device as passive device. >> + >> + VDD_xxx |--- A block (parent) >> + |--- B block (passive) >> + |--- C block (passive) >> + >> There are a little different composition among Exynos SoC because e= ach Exynos >> SoC has different sub-blocks. Therefore, shch difference should be = specified >=20 > s/shch/such/ I'll fix it on patch2 because this typo happen on patch2. >=20 >> in devicetree file instead of each device driver. In result, this d= river >> is able to support the bus frequency for all Exynos SoCs. >> =20 >> -Required properties for bus device: >> +Required properties for all bus devices: >> - compatible: Should be "samsung,exynos-bus". >> - clock-names : the name of clock used by the bus, "bus". >> - clocks : phandles for clock specified in "clock-names" property. >> - operating-points-v2: the OPP table including frequency/voltage in= formation >> to support DVFS (Dynamic Voltage/Frequency Scaling) feature. >> + >> +Required properties only for parent bus device: >> - vdd-supply: the regulator to provide the buses with the voltage. >> - devfreq-events: the devfreq-event device to monitor the current u= tilization >> of buses. >> =20 >> -Optional properties for bus device: >> +Required properties only for passive bus device: >> +- devfreq: the parent bus device. >> + >> +Optional properties only for parent bus device: >> - exynos,saturation-ratio: the percentage value which is used to ca= librate >> the performance count against total cycle count. >> - exynos,voltage-tolerance: the percentage value for bus voltage to= lerance >> @@ -34,7 +58,20 @@ Example1: >> power line (regulator). The MIF (Memory Interface) AXI bus is used= to >> transfer data between DRAM and CPU and uses the VDD_MIF regualtor. >=20 > s/regualtor/regulator/ ditto. >=20 >=20 > Acked-by: Krzysztof Kozlowski Thanks for your review. Best Regards, Chanwoo Choi