Messages in this thread | | | Subject | Re: [PATCH v7 2/2] soc/imx: Add GPCv2 power gating driver | From | Lucas Stach <> | Date | Fri, 31 Mar 2017 14:28:11 +0200 |
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Hi Dong,
Am Samstag, den 01.04.2017, 12:10 +0800 schrieb Dong Aisheng: [...] > > If we need the domains to be up before the consumers, the only > > way to deal with that is to select CONFIG_PM and > > CONFIG_PM_GENERIC_DOMAINS from the platform, so we have proper probe > > defer handling for consumer devices of the power domains. > > > > A bit confuse about these words...
If those options are selected we get proper PROBE_DEFER handling for consumers of the power domain, so probe order doesn't matter.
> > > Personally i'd be more like Rockchip's power domain implementation. > > > > Why? > > > > > See: > > > arch/arm/boot/dts/rk3288.dtsi > > > drivers/soc/rockchip/pm_domains.c > > > Dcumentation/devicetree/bindings/soc/rockchip/power_domain.txt > > > > > > How about refer to the Rockchip's way? > > > > Why? We just changed the way how it's done for GPCv1, after more than 1 > > year of those patches being on the list. Why should we do it differently > > for GPCv2? > > > > Hmm? > > I just thought your GPCv1 change was picked a few weeks ago (Feb 17 2017) > and there's no current users in kernel of the new binding. > That's why i come out of the idea if we could improve it before any users. > > Maybe i made mistake?
The patches to change this have been out for over 1 year. I'm less than motivated to change the binding again, after it has gone through the DT review and has finally been picked up.
> See: > commit 721cabf6c6600dbe689ee2782bc087270e97e652 > Author: Lucas Stach <l.stach@pengutronix.de> > Date: Fri Feb 17 20:02:44 2017 +0100 > > soc: imx: move PGC handling to a new GPC driver > > This is an almost complete re-write of the previous GPC power gating control > code found in the IMX architecture code. It supports both the old and the new > DT binding, allowing more domains to be added later and generally makes the > driver easier to extend, while keeping compatibility with existing DTBs. > > As the result, all functionality regarding the power gating controller > gets removed from the IMX architecture GPC driver. It keeps only the > IRQ controller code in the architecture, as this is closely coupled to > the CPU idle implementation. > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de> > Signed-off-by: Shawn Guo <shawnguo@kernel.org> > > > > > > > Then it could also address our issues and the binding would be > > > still like: > > > gpc: gpc@303a0000 { > > > compatible = "fsl,imx7d-gpc"; > > > reg = <0x303a0000 0x1000>; > > > interrupt-controller; > > > interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>; > > > #interrupt-cells = <3>; > > > interrupt-parent = <&intc>; > > > > > > pgc { > > > #address-cells = <1>; > > > #size-cells = <0>; > > > > > > pgc_pcie_phy: power-domain@IMX7_POWER_DOMAIN_PCIE_PHY { > > > reg = <IMX7_POWER_DOMAIN_PCIE_PHY>; > > > power-supply = <®_1p0d>; > > > clocks = <xxx>; > > > }; > > > > > > .... > > > }; > > > }; > > > > > > It also drops #power-domain-cells and register domain by > > > one provider with multi domains which is more align with HW. > > > > > > How do you think of it? > > > > How is this more aligned with the hardware? Both options are an > > arbitrary abstraction chosen in the DT binding. > > > > GPC is a Power Controller which controls multi power domains to subsystem > by its different registers bits. > e.g. PCIE/MIPI/USB HSIC PHY. > • 0xC00 ~ 0xC3F: PGC for MIPI PHY > • 0xC40 ~ 0xC7F: PGC for PCIE_PHY > • 0xD00 ~ 0xD3F: PGC for USB HSIC PHY > > So i thought it looks more like GPC is a power domain provider with multi > domains support to different subsystems from HW point of view. > > Isn't that true?
Linux and hardware devices are not required to match 1:1. There is nothing that would make subdividing a single hardware device into multiple ones bad style.
> > And there's also other two concerns: > First, current genpd sysfs output still not include provider. > e.g. > root@imx6qdlsolo:~# cat /sys/kernel/debug/pm_genpd/pm_genpd_summary > domain status slaves > /device runtime status > ---------------------------------------------------------------------- > PU off-0 > /devices/soc0/soc/130000.gpu suspended > /devices/soc0/soc/134000.gpu suspended > /devices/soc0/soc/2204000.gpu suspended > /devices/soc0/soc/2000000.aips-bus/2040000.vpu suspended > ARM off-0 > > I wonder it might be a bit mess once the provider is added while each > domain is registered as a virtual provider.
The provider is a Linux device. Linux devices don't necessarily have to correspond to hardware devices. There is no such rule.
> > Second, it sacrifices a bit performance when look-up PM domain in > genpd_get_from_provider if every domain is a provider. > The performance penalty of a list walk won't hurt us in the probe path, where we are (re-)probing entire devices. There is a lot more going on than a simple list walk.
> Though it is arguable that currently only 3 domains support on MX7, > but who knows the future when it becomes much more. > > However, i did see many exist users in kernel using one provider one > domain way. Maybe i'm over worried and it's not big deal.
I see that one provider with multiple domains is used more often, that doesn't means it's necessarily better. At least I haven't hear a convincing argument on why the chosen implementation in the GPC driver is worse than the alternative.
Regards, Lucas
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