On Thu, Oct 2, 2014 at 9:40 AM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > Hi, > > On 10/02/2014 03:34 PM, jonsmirl@xxxxxxxxx wrote: >> On Thu, Oct 2, 2014 at 9:23 AM, Michal Suchanek <hramrach@xxxxxxxxx> wrote: >>> On 2 October 2014 14:56, jonsmirl@xxxxxxxxx <jonsmirl@xxxxxxxxx> wrote: >>>> On Thu, Oct 2, 2014 at 8:39 AM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >>>>> Hi, >>>>> >>>>> On 10/02/2014 02:22 PM, jonsmirl@xxxxxxxxx wrote: >>>>>> On Thu, Oct 2, 2014 at 2:42 AM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >>>>>>> Hi, >>>>>>> >>>>>>> On 10/01/2014 08:12 PM, Stephen Warren wrote: >>>>>>>> On 10/01/2014 11:54 AM, jonsmirl@xxxxxxxxx wrote: >>>>>>>>> On Wed, Oct 1, 2014 at 1:26 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >>>>>>>> ... >>>>>>>>>> We've been over all this again and again and again. >>>>>>>>>> >>>>>>>>>> AAAARRRRRGGGGGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH! >>>>>>>>>> >>>>>>>>>> All solutions provided sofar are both tons more complicated, then the >>>>>>>>>> simple solution of simply having the simplefb dt node declare which >>>>>>>>>> clocks it needs. And to make things worse all of them sofar have >>>>>>>>>> unresolved issues (due to their complexity mostly). >>>>>>>>>> >>>>>>>>>> With the clocks in the simplefb node, then all a real driver has to do, >>>>>>>>>> is claim those same clocks before unregistering the simplefb driver, >>>>>>>>>> and everything will just work. >>>>>>>>>> >>>>>>>>>> Yet we've been discussing this for months, all because of some >>>>>>>>>> vague worries from Thierry, and *only* from Thierry that this will >>>>>>>>>> make simplefb less generic / not abstract enough, while a simple >>>>>>>>>> generic clocks property is about as generic as things come. >>>>>>>> >>>>>>>> Note: I haven't been following this thread, and really don't have the time to get involved, but I did want to point out one thing: >>>>>>>> >>>>>>>> As I think I mentioned very early on in this thread, one of the big concerns when simplefb was merged was that it would slowly grow and become a monster. As such, a condition of merging it was that it would not grow features like resource management at all. That means no clock/regulator/... support. It's intended as a simple stop-gap between early platform bringup and whenever a real driver exists for the HW. If you need resource management, write a HW-specific driver. The list archives presumably have a record of the discussion, but I don't know the links off the top of my head. If nobody >>>>>>>> other than Thierry is objecting, presumably the people who originally objected simply haven't noticed this patch/thread. I suppose it's possible they changed their mind. >>>>>>>> >>>>>>>> BTW, there's no reason that the simplefb code couldn't be refactored out into a support library that's used by both the simplefb we currently have and any new HW-specific driver. It's just that the simplefb binding and driver shouldn't grow. >>>>>>> >>>>>>> The whole reason why we want to use simplefb is not just to get things >>>>>>> running until HW specific driver is in place, but also to have early console >>>>>>> output (to help debugging boot problems on devices without a serial console), >>>>>>> in a world where most video drivers are build as loadable modules, so we >>>>>>> won't have video output until quite late into the boot process. >>>>>> >>>>>> You need both. >>>>>> >>>>>> 1) temporary early boot console -- this is nothing but an address in >>>>>> RAM and the x/y layout. The character set from framebuffer is built >>>>>> into the kernel. The parallel to this is early-printk and how it uses >>>>>> the UARTs without interrupts. This console vaporizes late in the boot >>>>>> process -- the same thing happens with the early printk UART driver. >>>>>> EARLYPRINTK on the command line enables this. >>>>>> >>>>>> 2) a device specific driver -- this sits on initrd and it loaded as >>>>>> soon as possible. The same thing happens with the real UART driver for >>>>>> the console. CONSOLE= on the command line causes the transition. There >>>>>> is an API in the kernel to do this transition, I believe it is called >>>>>> set_console() but it's been a while. >>>>> >>>>> Eventually we need both, yes. But 1) should stay working until 2) loads, >>>>> not until some phase of the bootup is completed, but simply until 2) loads. >>>> >>>> No, that is where you get into trouble. The device specific driver has >>>> to go onto initrd where it can be loaded as early in the boot process >>>> as possible. >>>> >>>> Trying to indefinitely extend the life of the earlyprintk or >>>> earlyframeuffer is what causes problems. Doing that forces you to >>>> basically turn them into device specific drivers which do things like >>>> claiming device specific resources and gaining device specific >>>> dependency knowledge, things that shouldn't be in earlyframebuffer. >>>> >>> >>> No. When initrd is running boot has already finished as far as kernel >>> is concerned. >>> >>> And you have to extend the life of the simplefb from the time boot has >>> finished through the time kernel mounts initrd (or other root) and >>> hands over to userspace found on the initrd, through the time this >>> userspace searches for the kms driver and until the time it has >>> finally loaded if that ever succeeds. >> >> Does the clock and regulator cleanup happen before drivers can load >> off from initrd? I didn't think it did but I might be wrong. > > Yes the cleanup happens before the first userspace process starts, be > that the fake /sbin/init from the initrd, or the real /sbin/init if > no initrd is used. Does that init have to be running to get device drivers off from initrd? I thought the kernel was able to load them directly from initrd earlier. > >> So maybe a solution to this is to delay that cleanup until after >> initrd drivers have a chance to load. Of course it is not possible to >> delay it indefinitely (like for disk based loading) but delaying over >> initrd is a fixed limit. > > And delaying over the initrd is not helpful. Not having the real driver > load for whatever reasons, is not necessarily a boot blocking event, > and if it us just missing will not lead to any error messages. > > So the boot will continue normally with a black screen, and things are > still impossible to debug. > > Regards, > > Hans > -- Jon Smirl jonsmirl@xxxxxxxxx -- 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
