From: rnayak@ti.com (Rajendra Nayak)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: OMAP4: clock: Lock PLLs in the right sequence
Date: Thu, 8 Aug 2013 15:44:11 +0530 [thread overview]
Message-ID: <1375956851-842-1-git-send-email-rnayak@ti.com> (raw)
On OMAP4 we have clk_set_rate()s being done for a few
DPLL clock nodes, as part of the clock init code, since
the bootloaders no longer locks these DPLLs.
So we have a clk_set_rate() done for a ABE DPLL node (which
inturn locks it) followed by a clk_set_rate() for the USB DPLL.
With USB DPLL being in bypass, we have this parent->child
relationship thats formed while the clocks get registered.
dpll_abe_ck
|
V
dpll_abe_x2_ck
|
V
dpll_abe_m3x2_ck
|
V
usb_hs_clk_div_ck
|
V
dpll_usb_ck
This is because usb_hs_clk_div_ck is bypass clock for dpll_usb_ck.
So with this parent->child relationship in place, a clk_set_rate()
on ABE DPLL results eventually in a clk_set_rate() call on USB DPLL,
because CCF does a clk_change_rate() (as part of clk_set_rate()) on
all downstream clocks resulting from a rate change on the top clock.
So its important that we lock USB DPLL before we lock ABE DPLL.
Without which we see these error logs at boot.
[These error logs will not be seen if using a bootloader that locks
USB DPLL]
[ 0.000000] clock: dpll_usb_ck failed transition to 'locked'
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[ 0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[ 0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[ 0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[ 0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[ 0.000000] clock: trace_clk_div_ck: could not find divisor for target rate 0 for parent pmd_trace_clk_mux_ck
[ 0.000000] Division by zero in kernel.
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
---
arch/arm/mach-omap2/cclock44xx_data.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/arch/arm/mach-omap2/cclock44xx_data.c b/arch/arm/mach-omap2/cclock44xx_data.c
index 88e37a4..1d5b529 100644
--- a/arch/arm/mach-omap2/cclock44xx_data.c
+++ b/arch/arm/mach-omap2/cclock44xx_data.c
@@ -1707,6 +1707,18 @@ int __init omap4xxx_clk_init(void)
omap2_clk_disable_autoidle_all();
/*
+ * A set rate of ABE DPLL inturn triggers a set rate of USB DPLL
+ * when its in bypass. So always lock USB before ABE DPLL.
+ */
+ /*
+ * Lock USB DPLL on OMAP4 devices so that the L3INIT power
+ * domain can transition to retention state when not in use.
+ */
+ rc = clk_set_rate(&dpll_usb_ck, OMAP4_DPLL_USB_DEFFREQ);
+ if (rc)
+ pr_err("%s: failed to configure USB DPLL!\n", __func__);
+
+ /*
* On OMAP4460 the ABE DPLL fails to turn on if in idle low-power
* state when turning the ABE clock domain. Workaround this by
* locking the ABE DPLL on boot.
@@ -1718,13 +1730,5 @@ int __init omap4xxx_clk_init(void)
if (rc)
pr_err("%s: failed to configure ABE DPLL!\n", __func__);
- /*
- * Lock USB DPLL on OMAP4 devices so that the L3INIT power
- * domain can transition to retention state when not in use.
- */
- rc = clk_set_rate(&dpll_usb_ck, OMAP4_DPLL_USB_DEFFREQ);
- if (rc)
- pr_err("%s: failed to configure USB DPLL!\n", __func__);
-
return 0;
}
--
1.7.9.5
next reply other threads:[~2013-08-08 10:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-08 10:14 Rajendra Nayak [this message]
2013-08-09 1:18 ` [PATCH] ARM: OMAP4: clock: Lock PLLs in the right sequence Mike Turquette
2013-08-09 3:47 ` Paul Walmsley
2013-08-09 5:35 ` Mike Turquette
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