linux-kernel - Re: [PATCH AUTOSEL 4.19 102/177] nvmem: imx-ocotp: reset error status on probe

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Message-Id: <CF40B493-27C8-4DF4-BB43-624CC797B12C@armadeus.com>
Date:   Tue, 7 Jan 2020 20:29:12 +0100
From:   Sébastien Szymanski 
        <sebastien.szymanski@...adeus.com>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        Fabio Estevam <festevam@...il.com>
Subject: Re: [PATCH AUTOSEL 4.19 102/177] nvmem: imx-ocotp: reset error status
 on probe

Hi Lucas,

> On 7 Jan 2020, at 18:53, Lucas Stach <l.stach@...gutronix.de> wrote:
> 
> Hi Sébastien,
> 
> On Di, 2020-01-07 at 15:50 +0100, Sébastien Szymanski wrote:
>> On 12/10/19 10:31 PM, Sasha Levin wrote:
>>> From: Lucas Stach <l.stach@...gutronix.de>
>>> 
>>> [ Upstream commit c33c585f1b3a99d53920bdac614aca461d8db06f ]
>>> 
>>> If software running before the OCOTP driver is loaded left the
>>> controller with the error status pending, the driver will never
>>> be able to complete the read timing setup. Reset the error status
>>> on probe to make sure the controller is in usable state.
>>> 
>>> Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
>>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>>> Link: https://lore.kernel.org/r/20191029114240.14905-6-srinivas.kandagatla@linaro.org
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>>> ---
>>> drivers/nvmem/imx-ocotp.c | 4 ++++
>>> 1 file changed, 4 insertions(+)
>>> 
>>> diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
>>> index afb429a417fe0..926d9cc080cf4 100644
>>> --- a/drivers/nvmem/imx-ocotp.c
>>> +++ b/drivers/nvmem/imx-ocotp.c
>>> @@ -466,6 +466,10 @@ static int imx_ocotp_probe(struct platform_device *pdev)
>>> 	if (IS_ERR(priv->clk))
>>> 		return PTR_ERR(priv->clk);
>>> 
>>> +	clk_prepare_enable(priv->clk);
>>> +	imx_ocotp_clr_err_if_set(priv->base);
>>> +	clk_disable_unprepare(priv->clk);
>>> +
>>> 	priv->params = of_device_get_match_data(&pdev->dev);
>>> 	imx_ocotp_nvmem_config.size = 4 * priv->params->nregs;
>>> 	imx_ocotp_nvmem_config.dev = dev;
>>> 
>> 
>> Hi,
>> 
>> This patch makes kernel 4.19.{92,93} hang at boot on my i.MX6ULL based
>> board. It hanks at
>> 
>> [    3.730078] cpu cpu0: Linked as a consumer to regulator.2
>> [    3.737760] cpu cpu0: Linked as a consumer to regulator.3
>> 
>> Full boot log is here: https://pastebin.com/TS8EFxkr
>> 
>> The config is imx_v6_v7_defconfig.
>> 
>> Reverting it makes the kernels boot again.
> 
> Can you check if it actually hangs in imx_ocotp_clr_err_if_set(), or if
> the clk_disable_unprepare() is the culprit?
> 
> If the clock disable hangs the system there is a missing clock
> reference somewhere else that we need to track down.

Yes, the system hangs in the imx6q-cpufreq driver, here:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/cpufreq/imx6q-cpufreq.c?h=v4.19.93#n322

Kernel 5.4.8 works thanks to commits:

2733fb0d0699 (“cpufreq: imx6q: read OCOTP through nvmem for imx6ul/imx6ull”)
92f0eb08c66a ("ARM: dts: imx6ul: use nvmem-cells for cpu speed grading”)

Regards,

-- 
Sébastien Szymanski, Armadeus Systems
Software engineer

> 
> Regards,
> Lucas
>