This patch fixes a bug, that prevents the Allwinner A83T and the A80 from a successful boot.
The bug is there since v4.16-rc1 and appeared after the clk branch was merged. 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 <embe...@gmail.com> --- Changes in v4: * add more information to the comment Changes in v3: * add information when the bug appeared * make the comment more clear 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 | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c index 8ff9dc3fe5bf..08ca8c46a8ff 100644 --- a/drivers/rtc/rtc-ac100.c +++ b/drivers/rtc/rtc-ac100.c @@ -183,7 +183,29 @@ 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; + + /* + * The clock has two parents, one is a fixed clock which is + * internally registered by the ac100 driver. The other parent + * is a clock from the codec side of the chip, which we + * properly declare and reference in the devicetree and is + * not implemented in any driver right now. + * If the clock core looks for the parent of that second + * missing clock, it can't find one that is registered and + * returns NULL. + * So we end up in a situation where clk_hw_get_num_parents + * returns the amount of clocks we can be parented to, but + * clk_hw_get_parent_by_index will not return the orphan + * clocks. + * Thus we need to check if the parent exists before + * we get the parent rate, so we could use the RTC + * without waiting for the codec to be supported. + */ + if (!parent) + continue; + + prate = clk_hw_get_rate(parent); tmp = ac100_clkout_round_rate(hw, req->rate, prate); -- 2.11.0 -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
