linux-kernel - Re: [PATCH v2 2/3] microblaze: remove redundant early

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Message-ID: <CAL_JsqJGvf1deWwqTxGaj5fKSL6eTvoY4gQ3Pn8x6YF6W7NMkg@mail.gmail.com>
Date:   Mon, 23 Apr 2018 11:34:29 -0500
From:   Rob Herring <robh@...nel.org>
To:     Michal Simek <monstr@...str.eu>
Cc:     Michal Simek <michal.simek@...inx.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] microblaze: remove redundant early_printk support

On Mon, Apr 23, 2018 at 5:50 AM, Michal Simek <monstr@...str.eu> wrote:
> On 13.4.2018 16:11, Rob Herring wrote:
>> On Tue, Apr 10, 2018 at 8:44 AM, Michal Simek <michal.simek@...inx.com> wrote:
>>> Hi Rob,
>>>
>>> On 28.3.2018 04:06, Rob Herring wrote:
>>>> With earlycon support now enabled, the arch specific early_printk support
>>>> can be removed.
>>>
>>> earlycon is not the full replacement of early_printk support as is
>>> designed right now.
>>> Definitely current early_printk is pretty old and contains code
>>> duplication but it starts much earlier then earlycon.
>>
>> Yes, essentially it's after MMU enabling rather than before. But it is
>> still before any h/w specific setup (dependent on the DT) which is
>> where one would typically fail to boot. Generally, I've found before
>> DT unflattening to be early enough. What can go wrong at this early
>> stage? Memory is flaky or you've passed in bad memory ranges or image
>> locations. An earlier console may or may not help there and those
>> problems are easier to debug in the bootloader.
>>
>> So it is a question of what you want to maintain.
>>
>>>> Signed-off-by: Rob Herring <robh@...nel.org>
>>>> Cc: Michal Simek <monstr@...str.eu>
>>>> ---
>>>> v2:
>>>> - Fix booting. The setup_memory call needed to be before the
>>>>   parse_early_param call.
>>>
>>> What's the reason for calling setup_memory before parse_early_param?
>>> Is there any dependency?
>>
>> Yes, either fixmap or ioremap (in your case) has to be functional when
>> earlycon is setup which happens via parse_early_param.
>
> Ok. Let's add it and see if there is any issue. Do you have any code
> which depends on this series?

No, I don't.

Rob