nouveau nvaa clock missing break?

[Kees Cook]

Hi,

Just curious if this code is missing a "break" or not...

/drivers/gpu/drm/nouveau/core/subdev/clock/nvaa.c: 373 in nvaa_clock_prog()

switch (priv->vsrc) {
case nv_clk_src_cclk:
mast |= 0x00400000;
default:
nv_wr32(clk, 0x4600, priv->vdiv);
}

Coverity noticed it as CID 1135671. If it's intentional, it might be
nice to add a "fall through" comment there.

Coverity also complained about read_pll (CID 1135670) where post_div
could (unlikely) be 0 and used for a divide-by-zero.

Thanks!

-Kees

--
Kees Cook
Chrome OS Security
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[Roy Spliet]

Hello Kees,

Thanks for your feedback. Let me first reassure you that this fall-through is indeed intentional: vdiv should be set regardless of the clock source. A comment line would definitely be in place though for future nouveau hackers.
In read_pll, post_div can never be zero in valid execution. If the register-read returns zero, the GPU has either fallen off the bus, or crashed because someone set a divider of 0. I agree that this is not very robust and will probably lead to a divide-by-zero on hardware failure. Checking it doesn't harm I bet!
I will propose a patch addressing these issues as soon as I find some free time. Thanks again for the feedback. Yours,

Roy

--- Ursprüngliche Nachricht ---
Von: Kees Cook <kees...@google.com>
Datum: 20:51:22 26-12-2013
An: Roy Spliet <rsp...@eclipso.eu>
Betreff: nouveau nvaa clock missing break?