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authorPhilipp Rossak <embed3d@gmail.com>2018-02-27 00:19:01 +0300
committerAlexandre Belloni <alexandre.belloni@bootlin.com>2018-03-17 16:20:50 +0300
commit561f8281cf90051bc5f11017ac5ebb21eec45ad9 (patch)
tree939372d1a1b0d4ca44736d59ceb03ba8cc0283c8 /drivers/rtc/rtc-ac100.c
parent188306ac9536ec47674ffa9dd330f69927679aeb (diff)
downloadlinux-561f8281cf90051bc5f11017ac5ebb21eec45ad9.tar.xz
rtc: ac100: Fix ac100 determine rate bug
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 <embed3d@gmail.com> Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Diffstat (limited to 'drivers/rtc/rtc-ac100.c')
-rw-r--r--drivers/rtc/rtc-ac100.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
index 080e3c04be43..3fe576fdd45e 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);