This patch fixes a bug, that prevents the Allwinner A83T and the A80 from a successful boot. You can find the shortend trace below: Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = (ptrval) [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: CPU: 0 PID: 49 Comm: kworker/0:1 Not tainted 4.15.0-10190-gb89e32ccd1be #2 Hardware name: Allwinner sun8i Family Workqueue: events deferred_probe_work_func PC is at clk_hw_get_rate+0x0/0x34 LR is at ac100_clkout_determine_rate+0x48/0x19c [ ... ] (clk_hw_get_rate) from (ac100_clkout_determine_rate+0x48/0x19c) (ac100_clkout_determine_rate) from (clk_core_set_rate_nolock+0x3c/0x1a0) (clk_core_set_rate_nolock) from (clk_set_rate+0x30/0x88) (clk_set_rate) from (of_clk_set_defaults+0x200/0x364) (of_clk_set_defaults) from (platform_drv_probe+0x18/0xb0) To fix that bug, we first check if the return of the clk_hw_get_parent_by_index is non zero. If it is zero we skip that clock parent. The BUG report could be found here: https://lkml.org/lkml/2018/2/10/198 Fixes: 04940631b8d2 ("rtc: ac100: Add clk output support") Signed-off-by: Philipp Rossak <embed3d@xxxxxxxxx> --- Changes in v2: * add tag Fixes: ... to commit message * add comment to if statement why we are doing this check drivers/rtc/rtc-ac100.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c index 8ff9dc3fe5bf..ba73201d8cc1 100644 --- a/drivers/rtc/rtc-ac100.c +++ b/drivers/rtc/rtc-ac100.c @@ -183,7 +183,17 @@ static int ac100_clkout_determine_rate(struct clk_hw *hw, for (i = 0; i < num_parents; i++) { struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i); - unsigned long tmp, prate = clk_hw_get_rate(parent); + unsigned long tmp, prate; + + /* + * We purposefully left open the possibility to use the clock + * from the codec side but it is not implemented right now. + * Thus we need to check if the parent exists. + */ + if (!parent) + continue; + + prate = clk_hw_get_rate(parent); tmp = ac100_clkout_round_rate(hw, req->rate, prate); -- 2.11.0
