linux-kernel - Re: [PATCH v1 3/3] arm64: dts: mt7622: Drop the general purpose timer node

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Date:   Fri, 23 Nov 2018 18:07:00 +0100
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Ryder Lee <ryder.lee@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Weijie Gao <weijie.gao@...iatek.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH v1 3/3] arm64: dts: mt7622: Drop the general purpose timer
 node



On 12/11/2018 02:28, Ryder Lee wrote:
> The crash http://termbin.com/zitb is caused by the timer register
> into system in early pahse during kernel boot, but the clock
> sources didn't get ready at that time.
> 
> A better way is to switch to use CLK_OF_DECLARE() in driver for things
> that need them early, but this node is actually useless in MT7622.
> So we drop it.

I suppose the root cause is, that the driver doesn't check the error
timer_of_init returned.

Would you mind to test the following patch to see if this fixes the problem?

--->8
>From be91e56ed527261137335af340845eb3dd3dd33a Mon Sep 17 00:00:00 2001
From: Matthias Brugger <matthias.bgg@...il.com>
Date: Fri, 23 Nov 2018 17:04:08 +0100
Subject: [PATCH] clocksource/drivers/timer-mediatek: error out on probe defer

If the clocks are not yet present, because they are loaded after
the timer is initialized, we are unable to boot.
Check if the return value of timer_of_init and return on EPROBE_DEFER.

Error seen is:
[    0.008337] Failed to get clock for /timer@...04000
[    0.013435] WARNING: CPU: 0 PID: 0 at ../drivers/clk/clk.c:3615
__clk_put+0xf0/0x120
[    0.021453] Modules linked in:
[    0.024614] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
4.20.0-rc1-00063-g2859d9abd7e8 #2
[    0.032902] Hardware name: MediaTek MT7622 RFB1 board (DT)
[    0.038580] pstate: 20000085 (nzCv daIf -PAN -UAO)
[    0.043538] pc : __clk_put+0xf0/0x120
[    0.047328] lr : clk_put+0xc/0x18
[    0.050753] sp : ffff000009163ed0
[    0.054178] x29: ffff000009163ed0 x28: 0000000041010018
[    0.059676] x27: 0000000000000000 x26: 0000000000000000
[    0.065174] x25: ffff0000090cb008 x24: ffff80001dfd7800
[    0.070672] x23: ffff000008f934b8 x22: ffff80001dfdeae0
[    0.076169] x21: ffff80001dfdeae0 x20: fffffffffffffdfb
[    0.081668] x19: ffff00000929ac40 x18: ffffffffffffffff
[    0.087166] x17: 0000000000000000 x16: 0000000000000000
[    0.092664] x15: ffff0000091696c8 x14: ffff0000892cd70f
[    0.098162] x13: ffff0000092cd71d x12: ffff000009181348
[    0.103661] x11: ffff000009181000 x10: 0000000005f5e0ff
[    0.109159] x9 : 0000000000000040 x8 : ffff000009181400
[    0.114657] x7 : ffff80001c800270 x6 : 0000000000000000
[    0.120155] x5 : ffff80001c800248 x4 : 0000000000000000
[    0.125653] x3 : 0000000000000000 x2 : 0000000000000000
[    0.131151] x1 : 0000000000000000 x0 : fffffffffffffdfb
[    0.136649] Call trace:
[    0.139175]  __clk_put+0xf0/0x120
[    0.142605]  timer_of_cleanup+0x60/0x7c
[    0.146572]  mtk_gpt_init+0x18c/0x1a0
[    0.150359]  timer_probe+0x74/0x10c
[    0.153969]  time_init+0x14/0x44
[    0.157307]  start_kernel+0x29c/0x414
[    0.161098] ---[ end trace c3137b005300b618 ]---

Fixes: a0858f937960 ("clocksource/drivers/timer-mediatek: Convert the driver to
timer-of")
Fixes: e3af677607d9 ("clocksource/drivers/timer-mediatek: Add support for system
timer")
Signed-off-by: Matthias Brugger <matthias.bgg@...il.com>
---
 drivers/clocksource/timer-mediatek.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/timer-mediatek.c
b/drivers/clocksource/timer-mediatek.c
index eb10321f8517..d40c77a65b08 100644
--- a/drivers/clocksource/timer-mediatek.c
+++ b/drivers/clocksource/timer-mediatek.c
@@ -276,8 +276,12 @@ static int __init mtk_syst_init(struct device_node *node)
 	to.of_irq.handler = mtk_syst_handler;

 	ret = timer_of_init(node, &to);
-	if (ret)
+	if (ret) {
+		if (ret == -EPROBE_DEFER)
+			return ret;
+
 		goto err;
+	}

 	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
 					TIMER_SYNC_TICKS, 0xffffffff);
@@ -301,8 +305,12 @@ static int __init mtk_gpt_init(struct device_node *node)
 	to.of_irq.handler = mtk_gpt_interrupt;

 	ret = timer_of_init(node, &to);
-	if (ret)
+	if (ret) {
+		if (ret == -EPROBE_DEFER)
+			return ret;
+
 		goto err;
+	}

 	/* Configure clock source */
 	mtk_gpt_setup(&to, TIMER_CLK_SRC, GPT_CTRL_OP_FREERUN);
-- 
2.19.1