linux-kernel - Re: [linux-sunxi] [PATCH 2/4] drivers: soc: sunxi: fix error processing on base address when claiming

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Message-ID: <CAGb2v67Mxq+y6mEKQ10y+vod5mxT=0Kz8dMPKC46By2-LO3EAg@mail.gmail.com>
Date:   Fri, 18 Aug 2017 14:29:35 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH 2/4] drivers: soc: sunxi: fix error
 processing on base address when claiming

On Fri, Aug 18, 2017 at 2:23 PM, Icenowy Zheng <icenowy@...c.io> wrote:
>
>
> 于 2017年8月18日 GMT+08:00 下午2:21:07, Chen-Yu Tsai <wens@...e.org> 写到:
>>Hi,
>>
>>On Wed, Aug 9, 2017 at 4:56 PM, Icenowy Zheng <icenowy@...c.io> wrote:
>>> When claiming SRAM, if the base is set to an error, it means that the
>>> SRAM controller has been probed, but failed to remap the controller
>>> memory zone. If the base is zero, thus the SRAM controller should be
>>not
>>> probed at all, and it should return -EPROBE_DEFER. However, currently
>>we
>>> returned -EPROBE_DEFER in the former situation, and ignored the
>>latter
>>> situation (which will lead to the kernel to panic).
>>>
>>> Fix the behavior on abnormal base address processing when claiming.
>>
>>Could you describe how you actually ran into this? The failure seems
>>unlikely for a properly written device tree.
>
> In fact it's possible, as the probe defering used to be broken.
>
> On the A64 situation, the SRAM is referenced by the DE2 CCU driver, which
> will be probed very early -- before SRAM is probed, and the problem happens.

OK. I see it's because the DE block's address if before almost everything
else. I was wondering why we never ran into this before.

Given there are no actual users in the kernel that could trigger this,
I'll queue this for 4.14 instead.

ChenYu