On Sun, Jun 12, 2016 at 03:29:01PM +0800, Peter Chen wrote: > On Fri, Jun 10, 2016 at 12:30:56PM -0500, Rob Herring wrote: > > On Thu, Jun 09, 2016 at 01:42:02PM +0200, Krzysztof Kozlowski wrote: > > > On 06/09/2016 12:29 PM, Mark Brown wrote: > > > > On Thu, Jun 09, 2016 at 11:44:18AM +0200, Krzysztof Kozlowski wrote: > > > >> Few drivers have a need of getting regulator supplies without knowing > > > >> their names: > > > >> 1. The Simple Framebuffer driver works on setup provided by bootloader > > > >> (outside of scope of kernel); > > > >> 2. Generic power sequence driver may be attached to any device node. > > > >> > > > >> Add a Device Tree helper for parsing "-supply" properties and returning > > > >> allocated bulk regulator consumers. > > > > > > > > I'm still very concerned that this is just an invitation to people to > > > > write half baked regulator consumers and half baked DTs to go along with > > > > it, making it a standard API that doesn't have big red flags on it that > > > > will flag up when "normal" drivers use it is not good. Right now this > > > > just looks like a standard API and people are going to just start using > > > > it. If we are going to do this perhaps we need a separate header or > > > > something to help flag this up. > > > > > > No problem, I can move it to a special header. Actually, if you dislike > > > this as an API, it does not have to be in header at all. I can just > > > duplicate the simplefb code. > > > > > > > In the case of power sequences I'd expect the sequences to perform > > > > operations on named supplies - the core shouldn't know what the supplies > > > > are but the thing specifying the sequence should. > > > > > > Hm, so maybe passing names like: > > > > > > usb3503@08 { > > > reset-gpios = <&gpx3 5 GPIO_ACTIVE_HIGH>; > > > initial-mode = <1>; > > > vdd-supply = <&buck8_reg>; > > > foo-supply = <&buck9_reg>; > > > > > > power-sequence; > > > power-sequence-supplies = "vdd", "foo"; > > > > This alone would be fine as it is just one property, but then what's > > next? power-sequence-delay, power-sequence-clocks, etc. What if you > > need to express ordering relationship of supplies, clocks, gpios? We end > > up with a scripting language in DT and we don't want to have that. > > > > Can we do things like below: > > - DT describes hardware elements (clock, gpios, etc) for power sequence, and we > need a node for power sequence. > - Power sequence framework handles getting hardware elements. Framework may do few things, since hardware elements are also different for devices. > - Power sequence platform driver handles special sequence for devices, > and we can create some generic drivers for generic devices. > So, my suggestion is do like mmc does (like this patch set does). The reasons like belows: - This piece of power sequence code needs to work like device driver, not library, it is easy to manage resources using device driver. - The device on the bus has still not been found, so this piece of code can't be in device driver on each subsystem. - We need to have a place for these power sequences drivers Ideally, I hope it can work like regulator class, but it seems hard to compatible with current mmc-pwrseq DT node. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html