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 <[email protected]>
---
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
On Mon, Feb 26, 2018 at 10:19:01PM +0100, Philipp Rossak wrote:
> 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 <[email protected]>
Acked-by: Maxime Ripard <[email protected]>
Thanks!
Maxime
--
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
On 26/02/2018 at 22:19:01 +0100, Philipp Rossak wrote:
> 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 <[email protected]>
> ---
>
> 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(-)
>
Applied, thanks.
--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com