Re: [PATCH v7 10/42] clk: davinci: New driver for davinci PSC clocks

From: David Lechner
Date: Wed Feb 28 2018 - 16:40:32 EST


On 02/28/2018 06:38 AM, Bartosz Golaszewski wrote:

I think I found the reason for the strange crashes we were
experiencing (emac core->name being NULL) thanks to Sekhar who pointed
me in the right direction.

The mdio driver fails to probe with v7 due to the supplied clock rate
being wrong. Before failing we register the emac clock with
pm_clk_add_clk(). When clock_ops puts the clock, it decreases the
reference count of the clock, but we never actually increased it in
the first place in the line above. The core clock code then destroys
the associated clk_core structure. When the next user comes around (in
our case the clk debug functions) the system crashes.

I believe there to be two issues: one is with v7 - we need to increase
the clock reference count in davinci_psc_genpd_attach_dev().

Second is the error path in the clock framework - we should remove the
destroyed clk_core from the debug list, which is not being done now.

Why we even need to track the refcount of clk_core is a mistery for me
though. Stephen, Mike?

Best regards,
Bartosz Golaszewski

Great find. I figured it had to be something like this, but I wasn't
able to reproduce the problem yet.

I suppose it is time to spin up a v8 with some fixes.