linux-kernel - Re: [PATCH V2 4/4] ARM64 LPC: support earlycon for UART connected to LPC

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Date:   Wed, 14 Sep 2016 14:36:39 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     zhichang <zhichang.yuan02@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Zhichang Yuan <yuanzhichang@...ilicon.com>,
        linuxarm@...wei.com, linux-kernel@...r.kernel.org,
        lorenzo.pieralisi@....com, minyard@....org,
        benh@...nel.crashing.org, gabriele.paoloni@...wei.com,
        john.garry@...wei.com, liviu.dudau@....com, zourongrong@...il.com
Subject: Re: [PATCH V2 4/4] ARM64 LPC: support earlycon for UART connected to LPC

On Wednesday, September 14, 2016 7:26:22 PM CEST zhichang wrote:
> 
> > 
> >> Hip06 LPC uart need two base addresses for earlycon.
> >> 2. the IO type is mmio to introduce a memory base address to access LPC register file. But the real uart
> >> IO type is UPIO_PORT. This is spcial...
> > 
> > This sounds like a deficiency in the of_setup_earlycon() function,
> > which can only handle MMIO addresses, and won't actually
> > be able to understand nodes without a "ranges" property like
> > you have here.
> > 
> Yes.
> The current of_setup_earlycon only support MMIO and the first reg property must be memory.
> 
> We can not support our LPC uart without any new code.
> But we can implement a private earlycon setup function and register
> it to the __earlycon_table, things will be ok.

I still think you should adapt of_setup_earlycon instead to handle IORESOURCE_IO
registers.

	Arnd