Quoting Douglas Anderson (2020-02-03 10:31:34)
> When I got my clock parenting slightly wrong I ended up with a crash
> that looked like this:
>
> Unable to handle kernel NULL pointer dereference at virtual
> address 0000000000000000
> ...
> pc : clk_hw_get_rate+0x14/0x44
> ...
> Call trace:
> clk_hw_get_rate+0x14/0x44
> _freq_tbl_determine_rate+0x94/0xfc
> clk_rcg2_determine_rate+0x2c/0x38
> clk_core_determine_round_nolock+0x4c/0x88
> clk_core_round_rate_nolock+0x6c/0xa8
> clk_core_round_rate_nolock+0x9c/0xa8
> clk_core_set_rate_nolock+0x70/0x180
> clk_set_rate+0x3c/0x6c
> of_clk_set_defaults+0x254/0x360
> platform_drv_probe+0x28/0xb0
> really_probe+0x120/0x2dc
> driver_probe_device+0x64/0xfc
> device_driver_attach+0x4c/0x6c
> __driver_attach+0xac/0xc0
> bus_for_each_dev+0x84/0xcc
> driver_attach+0x2c/0x38
> bus_add_driver+0xfc/0x1d0
> driver_register+0x64/0xf8
> __platform_driver_register+0x4c/0x58
> msm_drm_register+0x5c/0x60
> ...
>
> It turned out that clk_hw_get_parent_by_index() was returning NULL and
> we weren't checking. Let's check it so that we don't crash.
>
> Fixes: ac269395cdd8 ("clk: qcom: Convert to clk_hw based provider APIs")
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> ---
Applied to clk-next
