On 23/09/2012 18:46, Eric Nelson wrote:
Hi Stefano,
On 09/23/2012 08:56 AM, Stefano Babic wrote:
On 22/09/2012 16:37, Fabio Estevam wrote:
On Sat, Sep 22, 2012 at 10:42 AM, Otavio Salvador otavio@ossystems.com.br wrote:
Hello Eric,
On Fri, Sep 21, 2012 at 5:36 PM, Eric Nelson eric.nelson@boundarydevices.com wrote:
Signed-off-by: Eric Nelsoneric.nelson@boundarydevices.com
Did you test it in mx5 too? We seem to need to handle it in mx5 too as we had hungs in FSL kernel when using framebuffer in U-Boot. We're using a patch in kernel for workaround it but it seems your fix does what is need.
I have just tested Eric's series on a mx53loco and it does fix the kernel hang issue.
I made some comments on this series and hopefully Eric's v2 can get into 2012.10, since this is a bug fix.
Ok, I am waiting for V2 and I will push it.
I'll forward this later today.
Ok
Anyway, a question about the issue. It seems to me that it is not possible with IPUV3 (I have not tested myself, so my question) to get the u-boot splashscreen displayed on the LCD until the kernel has finished to boot. This could be possible (and it is possible on other SOC) if the IPU is loaded as module instead of statically linked to the kernel, and if the kernel does not touch the IPU setup. This means also that it should not disable the clocks used by U-Boot for the IPU.
I'm not sure I understand. The splash screen comes up as soon as the call to ipuv3_fb_init() is made (in board_video_skip() in my implementation for SABRE Lite).
As it stands, if we leave the IPU running, we'll see garbage on the display as the kernel re-purposes the RAM used by U-Boot's frame buffer.
Right, if the kernel reuse the same memory. I am aware that it is not implemented, I am asking if there some reason to make it impossible.
Some customers want to have a picture shown on the LCD until their application is running. This makes sense, because the application can take a lot of time before displaying something on the LCD.
If we reserve some memory for this scope, that is not used by the kernel later (passing the mem= parameter, for example, or using a .reserve entry in the board initialization code), we can reach the goal. In U-Boot we have a single display with 16bit, that means that the memory consumption is not very high.
But I understand from your patch that this way is not possible on iMX53/MX6, and IPU must be always disabled. Is this correct ?
Sascha responded to a note about this on AKML that the hand-over of a live FB isn't a supported kernel use case and it's definitely tricky.
And I agree with him, the handover is tricky and not easy, I mean, it can work with a SOC (it remains tricky..) but not with another one. What I am saying is not this, but what happens if the IPU is not touched until the IPU modules are loaded.
I don't know about the policy, but from a practical matter, the IPU frame buffer implementation in U-Boot isn't currently up to that task, since: it only supports a single display (i.MX6 can handle 4) it only supports 16bpp
Additional functionality would be helpful here.
Agree with you. And this is the reason I am not supposing that the kernel takes the IPU setup made by U-Boot. It could be a nightmare.
I would like to see a handoff of display settings from U-Boot to the kernel, but that's also a tricky thing as long as we're supporting different mechanisms (DT in main-line and kernel parameters in older kernels).
Yes, and a lot of other things. I know Anatolji implemented this behavior for a PPC5121, but we cannot generalize. I agree that the handoff is difficult and not maintainable. My question is different: if the IPU drivers in kernel are compiled as modules, and I will load them only after booting, and the framebuffer's memory is reserved so that the kernel does not touch it, is there still a known reason because the IPU should not run when we boot the kernel? I know this issue with USB, maybe we have now the same with the IPU.
Note: this has nothing to do with this patch ;-). I will merge it into the current release when you push V2.
Best regards, Stefano