Re: linux-next on Chromebook2: DRM failing to allocate

[Kevin Hilman <khilman@linaro.org>]

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Rahul Sharma <rahul.sharma@samsung.com> writes:

> On 11 June 2014 03:48, Kevin Hilman <khilman@linaro.org> wrote:
>> Hi Ajay,
>>
>> On Tue, Jun 10, 2014 at 1:51 PM, Ajay kumar <ajaynumb@gmail.com> wrote:
>>> Hi,
>>>
>>> On 6/11/14, Kevin Hilman <khilman@linaro.org> wrote:
>>>> On Tue, Jun 10, 2014 at 11:04 AM, Stéphane Marchesin
>>>> <marcheu@chromium.org> wrote:
>>>>> On Tue, Jun 10, 2014 at 10:56 AM, Kevin Hilman <khilman@linaro.org>
>>>>> wrote:
>>>>>> I'm trying to get the latest linux-next working on my Chromebook2
>>>>>> (it's booting to a serial console) and am now trying to get the
>>>>>> display working (at least for a frambuffer console.)
>>>>>>
>>>>>> Since the display nodes seem to be present in the exynos5800-peach-pi
>>>>>> DTS, I tried enabling DRM and it's failing to allocate memory (log
>>>>>> below[1]
>>>>>>
>>>>>> Is there some additional memory setup/allocations I should be doing?
>>>>>> maybe with CMA?
>>>>>
>>>>> Probably not CMA, but maybe you don't have the iommu enabled?
>>>>
>>>> Turns out it was missing CMA support.  Specifically:
>>>>    CONFIG_CMA=y
>>>>    CONFIG_DMA_CMA=y
>>>> are needed (my full .config is here: http://hastebin.com/uqopirazir.vbs)
>>>>
>>>> With that, it allocates, appears to detect the panel and even claims
>>>> "Console: switching to colour frame buffer device", but I don't see
>>>> tux or any output on the display (DRM debug output below).
>>>>
>>>> Note that I'm chain-loading nv_uboot from an SD card, and u-boot is
>>>> driving the display (black text on white background.)  As soon as it
>>>> starts the kernel though, u-boot seems to shut down the display
>>>> (though the backlight seems to still be on.)
>>>>
>>>> Maybe the DT for peach-pi is missing the regulator used to power the
>>>> panel, or maybe a GPIO used to power up the panel?
>>>>
>>>> Any ideas?
>>> Not only the DT patches, but few patches are missing to support the
>>> panel present on peach-pi.
>>> You should also take the following patches to be able to get the
>>> display up on peach-pi:
>>> http://www.spinics.net/lists/linux-samsung-soc/msg32122.html
>>
>> Excellent, thanks for the pointer to those patches.  I'll have a look.
>>
>> Can you confirm that this should work even when chain-loading
>> nv_uboot?  It appears u-boot is powering down the panel.
>
> If u-boot is powering down the panel, you also need EC and Tps DT
> patches to get regulators up in kernel. Those are not posted yet. I will
> send these patches to you.

I tested the patches you sent on top of next-2014060 but I'm still not
seeing tux on the framebuffer.  I do see the backlight turn off and back
on twice during the boot, but nothing else interesting on the display.

I've configured the kernel using the chromeos configs provided:

  ./chromeos/scripts/prepareconfig chromeos-exynos5

And then I append the some kconfig fragments[1] to enable DT append, and
enable the serial port.

>From the kernel messages, it appears that everything is working ok, but
I don't see anything on the display yet.  Attached is the .config used
and the boot log with drm.drm_debug=0xff.

Kevin

[1] 
CONFIG_OF=y
CONFIG_PROC_DEVICETREE=y
CONFIG_ARM_APPENDED_DTB=y
CONFIG_ARM_ATAG_DTB_COMPAT=y
CONFIG_SERIAL_SAMSUNG=y
CONFIG_SERIAL_SAMSUNG_CONSOLE=y
CONFIG_MALI_T6XX=n


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