HDLCD crashes with 6d910bfa809e

[liviu.dudau at arm.com]

On Tue, Jun 07, 2016 at 03:11:14PM +0100, Robin Murphy wrote:
> Hi Liviu,
> 
> On 07/06/16 14:35, liviu.dudau at arm.com wrote:
> >On Tue, Jun 07, 2016 at 01:06:00PM +0100, Robin Murphy wrote:
> >>Having just inadvertently merged -next into my working branch, I find
> >>dev6d910bfa809e ("drm/hlcd: Use lockless gem BO free callback") adversely
> >>affecting my board's ability to boot ;)
> >>
> >>Since I (intentionally) don't have sufficient CMA to create a framebuffer,
> >>drm_gem_cma_create() fails, unconditionally calls the now-NULL
> >>drm->driver->gem_free_object() in its cleanup path, and fiery death
> >>ensues...
> >
> >Thanks for reporting this. What other changes other than reducing the CMA
> >allocation size do you have that I might need in order to reproduce this?
> 
> I've just confirmed a plain checkout of next-20160602, using arm64 defconfig
> + DRM + HDLCD + TDA998X and CMA_SIZE_MBYTES=1, booted on a Juno, does the
> job:
> 
> [    3.032402] hdlcd 7ff60000.hdlcd: bound 0-0070 (ops tda998x_ops)
> [    3.038388] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [    3.044970] [drm] No driver support for vblank timestamp query.
> [    3.076973] hdlcd 7ff60000.hdlcd: failed to allocate buffer with size
> 7680000
> [    3.084081] Bad mode in Synchronous Abort handler detected, code
> 0x86000004 -- IABT (current EL)
> [    3.092815] CPU: 3 PID: 6 Comm: kworker/u12:0 Not tainted
> 4.7.0-rc1-next-20160602 #686
> [    3.100682] Hardware name: ARM Juno development board (r1) (DT)
> [    3.106567] Workqueue: deferwq deferred_probe_work_func
> [    3.111761] task: ffff8009768a3e80 ti: ffff8009768e8000 task.ti:
> ffff8009768e8000
> [    3.119198] PC is at 0x0
> [    3.121720] LR is at drm_gem_cma_create+0x128/0x130
> ...and so on.
> 
> Today's -next, on the other hand, dodges the bullet entirely:
> 
> [    2.903645] [drm] found ARM HDLCD version r0p0
> [    2.908122] hdlcd 7ff60000.hdlcd: master bind failed: -22
> [    2.913505] tda998x: probe of 0-0070 failed with error -22
> [    2.919141] [drm] found ARM HDLCD version r0p0
> [    2.923609] hdlcd 7ff50000.hdlcd: master bind failed: -22
> [    2.928991] tda998x: probe of 0-0071 failed with error -22

OK, the problem is that commit 59ce4039727ef40 has changed the behaviour from when
there is no "memory-region" phandle in the DT: before it used to return -ENODEV, now
it returns -EINVAL.

Marek, I quite liked the old behaviour to detect if the DT had the optional (from
my driver's point of view) "memory-region" phandle. Plus the check for dev is superfluous
when using of_reserved_mem_device_init() as that uses dev->of_node for np so it would
crash before the check anyway. Maybe move the check there?

Until then I suggest reverting the 59ce4039727ef40 commit.

Best regards,
Liviu

> 
> Oh well...
> 
> Robin.
> 

-- 
====================
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| but they're not |
| giving me the   |
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