Op 13 aug. 2014, om 09:54 heeft David Herrmann <dh.herrmann@xxxxxxxxx> het volgende geschreven: > Hi > > On Wed, Aug 13, 2014 at 9:17 AM, Luc Verhaegen <libv@xxxxxxxxx> wrote: >> This is needed for the sunxi platform, where the u-boot initialized display >> engine gets disabled by the clocks framework if certain clocks are not >> claimed. Once these clocks are disabled, register content is lost, and there >> is no turning back unless a full display driver is loaded, which kind of >> beats the purpose of having simplefb running. >> >> The lack of clock handling should plague more hardware, but so far rpi is the >> best known user of simplefb, and its stepmotherly handling of the arm core >> has kept these sort of issues from the kernel. >> >> The sunxi u-boot side code can be found here: >> https://groups.google.com/forum/#!topic/linux-sunxi/dPs958sIXvY >> >> Patch 3 might be controversial, as this does not achieve anything real today, >> since the status property in dt is only really evaluated when dealing with a >> nodes memory. It still seems like a good idea to at least flag this memory or >> node as disabled, as we really have no way back when the clocks get disabled. > > Hans de Goede shortly told me about this and, tbh, I am not very > pleased. Stephen tried to keep simplefd "as simple as possible", your > patch now adds hardware-specific features. To be fair, the patch is > simple and clocks are easy to handle, but I somehow fear we have to > add more and more hardware-support that is required to keep the > framebuffer active. This really defeats the purpose of simplefb. > > The biggest question I have, is why do you add the clocks to your DT > at all? The framebuffer is set up by your boot-loader (or maybe > platform code) and should prepare the clocks. I don't see why we add > the clocks to DT now. If they're not added, then no-one will disable > them and simplefb works just fine, right? All clocks known to linux without a consumer will get disabled on most (all?) ARM systems to save power. Years ago OMAP had a Kconfig option to change that behaviour and add printk warnings for the clocks it would touch. To be honest, I don't get why sunxi needs a simplefb to begin with, only a proper kms/drm driver is needed which would register the clocks it needs properly. These patches and discussion seem like a lot of effort wasted on the wrong thing. But I can't complain about that since I'm not the one doing the work. regards, Koen-- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
