Re: [PATCH] soc: imx8m: Increase the clock enable before reading the register

From: "Wang, Xiaolei" <xiaolei.wang@windriver.com>
To: Shawn Guo <shawnguo@kernel.org>
Cc: s.hauer@pengutronix.de, kernel@pengutronix.de,
	festevam@gmail.com, l.stach@pengutronix.de, linux-imx@nxp.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] soc: imx8m: Increase the clock enable before reading the register
Date: Fri, 11 Nov 2022 11:01:15 +0800	[thread overview]
Message-ID: <f0e35731-07df-bd80-329f-a5ad9818e1e8@windriver.com> (raw)
In-Reply-To: <20221111024607.GH125525@dragon>

On 11/11/2022 10:46 AM, Shawn Guo wrote:
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> On Fri, Oct 28, 2022 at 12:14:18PM +0800, Xiaolei Wang wrote:
>> When executing kdump to start the second kernel,
>> since IMX-OCOTP has turned off the clock, the clock
>> needs to be re-enabled, otherwise the system will hang.
>>
>> Fixes: ac34de14ac30 ("Revert "soc: imx8m: change to use platform driver"")
> Are you saying this fixes a regression caused by ac34de14ac30?

Yes,

Although there is a problem with commit 7d981405d0fd, it also solves the 
kexec kernel hang, commit 7d981405d0fd is reverted, and the kexec kernel 
hang will also be introduced, so the clock needs to be enabled when the 
kexec kernel starts.

thanks

xiaolei

>
> Shawn
>
>> Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
>> ---
>>   drivers/soc/imx/soc-imx8m.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/soc/imx/soc-imx8m.c b/drivers/soc/imx/soc-imx8m.c
>> index cc57a384d74d..28144c699b0c 100644
>> --- a/drivers/soc/imx/soc-imx8m.c
>> +++ b/drivers/soc/imx/soc-imx8m.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/platform_device.h>
>>   #include <linux/arm-smccc.h>
>>   #include <linux/of.h>
>> +#include <linux/clk.h>
>>
>>   #define REV_B1                               0x21
>>
>> @@ -56,6 +57,7 @@ static u32 __init imx8mq_soc_revision(void)
>>        void __iomem *ocotp_base;
>>        u32 magic;
>>        u32 rev;
>> +     struct clk *clk;
>>
>>        np = of_find_compatible_node(NULL, NULL, "fsl,imx8mq-ocotp");
>>        if (!np)
>> @@ -63,6 +65,13 @@ static u32 __init imx8mq_soc_revision(void)
>>
>>        ocotp_base = of_iomap(np, 0);
>>        WARN_ON(!ocotp_base);
>> +     clk = of_clk_get_by_name(np, NULL);
>> +     if (!clk) {
>> +             WARN_ON(!clk);
>> +             return 0;
>> +     }
>> +
>> +     clk_prepare_enable(clk);
>>
>>        /*
>>         * SOC revision on older imx8mq is not available in fuses so query
>> @@ -79,6 +88,8 @@ static u32 __init imx8mq_soc_revision(void)
>>        soc_uid <<= 32;
>>        soc_uid |= readl_relaxed(ocotp_base + OCOTP_UID_LOW);
>>
>> +     clk_disable_unprepare(clk);
>> +     clk_put(clk);
>>        iounmap(ocotp_base);
>>        of_node_put(np);
>>
>> --
>> 2.25.1
>>