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

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Message-ID: <ZsdR-G9S5nYbQX4s@finisterre.sirena.org.uk>
Date: Thu, 22 Aug 2024 15:58:00 +0100
From: Mark Brown <broonie@...nel.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>
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 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.

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