linux-kernel - Re: [PATCH -next] spi: stm32-qspi: Simpify resource lookup

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Message-ID: <765ccc96-a48c-8a7a-ebf4-344fec67d95f@huawei.com>
Date: Fri, 23 Aug 2024 14:22:59 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Mark Brown <broonie@...nel.org>
CC: <mcoquelin.stm32@...il.com>, <alexandre.torgue@...s.st.com>,
	<linux-spi@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] spi: stm32-qspi: Simpify resource lookup



On 2024/8/22 22:58, Mark Brown wrote:
> On Tue, Aug 20, 2024 at 08:37:07PM +0800, Jinjie Ruan wrote:
>> Use the devm_platform_ioremap_resource_byname() helper instead of
>> calling platform_get_resource_byname() and devm_ioremap_resource()
>> separately.
> 
> This breaks boot on the Avenger96 board, it causes a NULL pointer
> dereference:
> 
> [    2.350480] Unable to handle kernel NULL pointer dereference at virtual address 00000000 when read
> 
> ...
> 
> [    2.695787] Call trace:
> [    2.695807]  stm32_qspi_probe from platform_probe+0x5c/0xb0
> [    2.703914]  platform_probe from really_probe+0xc8/0x2c8
> [    2.709284]  really_probe from __driver_probe_device+0x88/0x19c
> [    2.715145]  __driver_probe_device from driver_probe_device+0x30/0x104
> 
> https://lava.sirena.org.uk/scheduler/job/650792
> 
>> -	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "qspi");
>> -	qspi->io_base = devm_ioremap_resource(dev, res);
>> +	qspi->io_base = devm_platform_ioremap_resource_byname(pdev, "qspi");
>>  	if (IS_ERR(qspi->io_base))
>>  		return PTR_ERR(qspi->io_base);
>>  
>>  	qspi->phys_base = res->start;
>>  
>> -	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "qspi_mm");
>> -	qspi->mm_base = devm_ioremap_resource(dev, res);
>> +	qspi->mm_base = devm_platform_ioremap_resource_byname(pdev, "qspi_mm");
>>  	if (IS_ERR(qspi->mm_base))
>>  		return PTR_ERR(qspi->mm_base);
> 
> I can't identify any obvious error here, these look like a direct
> subsitution - the implementation of devm_platform_ioremap_resource_byname()
> looks to be the same as the replaced code and dev is set to &pdev->dev
> but I'm seeing the above behaviour.

Sorry, from lkp@...el.com，I identify that the "res" returned by
platform_get_resource_byname() is used by "qspi->phys_base =
res->start;" later，so the devm_platform_ioremap_resource_byname() is not
inapplicable here.