[BISECTED] Nokia 770 framebuffer breakage

[Russell King - ARM Linux]

On Tue, Oct 20, 2015 at 01:24:13AM +0300, Aaro Koskinen wrote:
> On Mon, Oct 19, 2015 at 09:05:22PM +0100, Russell King - ARM Linux wrote:
> > On Mon, Oct 19, 2015 at 10:37:59PM +0300, Aaro Koskinen wrote:
> > > Hi,
> > > 
> > > Somewhere between 4.1 .. 4.3-rc6 framebuffer on Nokia 770 stopped working.
> > > 
> > > Bisection points to:
> > > 
> > > commit 2568999835d7797afce3dcc3a3f368051ffcaf1f
> > > Author: Russell King <rmk+kernel at arm.linux.org.uk>
> > > Date:   Mon Mar 2 15:40:29 2015 +0000
> > > 
> > >     clkdev: add clkdev_create() helper
> > > 
> > > The commit cannot be reverted cleanly from current trees, but I re-tested
> > > that commit 2568999835d7797afce3dcc3a3f368051ffcaf1f does not work and
> > > commit 2568999835d7797afce3dcc3a3f368051ffcaf1f^1 indeed works.
> > 
> > Really need more information than that, like a kernel log or something.
> 
> This is a device with normal consumer electronics mechnics so serial
> port access is PITA. However I managed to get a boot log, see below,
> it's from commit 2568999835d7797afce3dcc3a3f368051ffcaf1f.

Hmm, that points to a driver that doesn't bother checking whether it
successfully got any resources:

        hwa742.sys_ck = clk_get(NULL, "hwa_sys_ck");

        spin_lock_init(&hwa742.req_lock);

        if ((r = hwa742.int_ctrl->init(fbdev, 1, req_vram)) < 0)
                goto err1;

        if ((r = hwa742.extif->init(fbdev)) < 0)
                goto err2;

        ext_clk = clk_get_rate(hwa742.sys_ck);

There's no check here that clk_get() actually worked, and this will be
why you then end up with the division by zeros.  That's someone elses
problem though. :)

> > Can you try this patch please?
> 
> Unfortunately with the patch it dies even earlier, without any output.

It shouldn't (I've been through the resulting assembly code.)  I wonder
if this is fixing the problem, but it's now failing elsewhere instead.

What happens if you change it to:

	l = clkdev_create(r, alias, alias_dev_name);

which should be 100% identical to how older kernels behaved - if that
works, can you print out 'alias' and 'alias_dev_name' for every call
to clk_add_alias() and send that please?

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