linux-kernel - Re: CMA Regression issue - [PATCH v2] of: reserved_mem: Restructure code to call reserved mem init functions earlier

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Message-ID: <5c363e91-581c-4d33-ad5a-154da915b3fb@quicinc.com>
Date: Mon, 8 Jul 2024 16:10:01 -0700
From: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
To: Aisheng Dong <aisheng.dong@....com>
CC: Rob Herring <robh@...nel.org>,
        "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        Jason Liu <jason.hui.liu@....com>,
        "dongas86@...il.com" <dongas86@...il.com>,
        "saravanak@...gle.com"
	<saravanak@...gle.com>,
        Krzysztof Kozlowski <krzk@...nel.org>, <kernel@...cinc.com>
Subject: Re: CMA Regression issue - [PATCH v2] of: reserved_mem: Restructure
 code to call reserved mem init functions earlier


On 7/4/2024 4:41 AM, Aisheng Dong wrote:
> Hi Oreoluwa,
>
> We observed a CMA regression issue on MX8MN that the CMA region failed to be
> setup by rmem_cma_setup() since the following patch:
> f2a524d9ef5b ("of: reserved_mem: Restructure code to call reserved mem init functions earlier") [1]
> And the CMA node was incorrect parsed (e.g. non-reuseable) due to NULL node pointer.
> Below is one line boot log tested with the tag next-20240703 of linux-next tree.
> OF: reserved mem: 0x0000000058000000..0x000000007fffffff (655360 KiB) map non-reusable linux,cma
> NOTE: actually there is a reusable property:
> linux,cma {
>         compatible = "shared-dma-pool";
>         reusable;
>         size = <0 0x28000000>;
>         alloc-ranges = <0 0x40000000 0 0x40000000>;
>         linux,cma-default;
> };
>
> The root cause was that the CMA region was initialized at a very early stage
> since above commit in question.
> The call flow became:
> early_init_fdt_scan_reserved_mem()->fdt_scan_reserved_mem()->
> __reserved_mem_alloc_size()->of_reserved_mem_save_node(NULL, xxx)->
> of_init_reserved_mem_node()->__reserved_mem_init_node().
>
> The rmem->dev_node is still NULL when calling __reserved_mem_init_node()
> which fails to call the rmem_cma_setup().
>
> Please let me know if there's already a fix patch.
>
> [1] https://lore.kernel.org/all/20240620001027.2326275-1-quic_obabatun@quicinc.com/
>
> Regards
> Aisheng
Hi Aisheng,

I have uploaded a fix here:
https://lore.kernel.org/all/20240708230613.448846-1-quic_obabatun@quicinc.com/

Please test and see if this fixes the issue.

Thank you!
Oreoluwa