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

[Jinjie Ruan <ruanjinjie@xxxxxxxxxx>]

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.

Mark, thank you very much, I can't identify the error here too. This bug
may be easy to locate if have a reproduction environment, but it's good
to keep it the way it is.