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

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Message-ID: <5a8ad8dd-c768-3abe-9ea3-537cdb9b304c@gmail.com>
Date:   Mon, 26 Nov 2018 11:15:35 +0100
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Ryder Lee <ryder.lee@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Weijie Gao <weijie.gao@...iatek.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 3/3] arm64: dts: mt7622: Drop the general purpose timer
 node



On 26/11/2018 04:49, Ryder Lee wrote:
> On Fri, 2018-11-23 at 18:07 +0100, Matthias Brugger wrote:
>>
>> 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);
> 
> I tried this patch, but it didn't work. I think *_OF_DECLARE() is not
> compatible with EPROBE_DEFER.
> 
> I also found the similar discussion about this issue:
> https://patchwork.kernel.org/patch/10580345/
> 

Got it. So from my research we would need to use CLK_OF_DECLARE_DRIVER for:
    mainpll (pll)

    syspll4_d16 (div)

    f10m_ref_sel (mux)

    infra_apxgpt_pd (gate)

Anyway, as a quick fix we can delete the device node. I'll reword you commit
message and I'll also reword commit message for 1/3

In the future please try to not put links into the commit message but explain
what is happening.

Regards,
Matthias