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Subject: Re: [PATCH v11 3/6] arm64: dts: allwinner: Add Allwinner H616 .dtsi
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To:     Andre Przywara <andre.przywara@arm.com>,
        =?UTF-8?Q?Jernej_=c5=a0krabec?= <jernej.skrabec@gmail.com>
Cc:     Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Icenowy Zheng <icenowy@aosc.io>,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Samuel Holland <samuel@sholland.org>
Message-ID: <39537f95-2ed4-f526-5912-364c1c1ed512@sholland.org>
Date:   Thu, 7 Jul 2022 01:30:32 -0500
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Hi Andre, Jernej,

On 7/6/22 8:16 AM, Andre Przywara wrote:
> so after seemingly having finished writing this email, I realised that
> this won't really help, as I think this diverts the discussion. And the
> problem has been around for a while, and won't probably be solved easily
> or quickly. I think we agree to disagree here, or we should admit that
> there are different approaches ("bundled firmware" vs. "UEFI"), so in the
> interest of not blocking the H616 series:
> 
> Shall I just keep the firmware node? This would work both ways, whereas
> dropping the node would impede the "bundled firmware" approach?

Let me try to sum up the relevant portion of my thoughts (and save the rest for
elsewhere):

The only reason to add the reserved-memory node is to support externally-loaded
DTBs. By adding the node, we are committing to support externally-loaded DTBs on
this SoC.

Upgrading the kernel is not allowed to break boot. If we support
externally-loaded DTBs, that rule extends to DTBs shipped with the kernel.

If we remove the reserved-memory node, the combination of old U-Boot + new
externally-loaded DTB will stop booting (the kernel version is irrelevant).
Therefore, if we add the node, we can never remove it, full stop.

I will (begrudgingly) accept that, as long as the node matches what TF-A
actually generates today. That means, please:
 - Drop the label and update the node name
 - Reduce the size to 256 KiB, matching (BL31_LIMIT - BL31_BASE)

Regards,
Samuel