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Date:   Thu, 27 Oct 2022 11:28:34 +0200
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Subject: Re: [PATCH 7/7] arm64: dts: mediatek: Add support for MT6795 Sony
 Xperia M5 smartphone
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To:     Konrad Dybcio <konrad.dybcio@somainline.org>, robh+dt@kernel.org
Cc:     krzysztof.kozlowski+dt@linaro.org, vkoul@kernel.org,
        chaotian.jing@mediatek.com, ulf.hansson@linaro.org,
        matthias.bgg@gmail.com, hsinyi@chromium.org,
        nfraprado@collabora.com, allen-kh.cheng@mediatek.com,
        fparent@baylibre.com, sam.shih@mediatek.com,
        sean.wang@mediatek.com, long.cheng@mediatek.com,
        wenbin.mei@mediatek.com, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
        linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, phone-devel@vger.kernel.org,
        ~postmarketos/upstreaming@lists.sr.ht
References: <20220729104441.39177-1-angelogioacchino.delregno@collabora.com>
 <20220729104441.39177-8-angelogioacchino.delregno@collabora.com>
 <a8fa9e22-8c3f-60b2-a0db-01cfd5c37765@somainline.org>
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
In-Reply-To: <a8fa9e22-8c3f-60b2-a0db-01cfd5c37765@somainline.org>
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Precedence: bulk

Il 29/07/22 14:00, Konrad Dybcio ha scritto:
> 
> 
> On 29.07.2022 12:44, AngeloGioacchino Del Regno wrote:
>> Add a basic support for the Sony Xperia M5 (codename "Holly")
>> smartphone, powered by a MediaTek Helio X10 SoC.
>>
>> This achieves a console boot.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Hello Konrad,
First of all, I'm sorry for the very late reply.

>> ---
>>   arch/arm64/boot/dts/mediatek/Makefile         |  1 +
>>   .../dts/mediatek/mt6795-sony-xperia-m5.dts    | 90 +++++++++++++++++++
>>   2 files changed, 91 insertions(+)
>>   create mode 100644 arch/arm64/boot/dts/mediatek/mt6795-sony-xperia-m5.dts
>>
>> diff --git a/arch/arm64/boot/dts/mediatek/Makefile b/arch/arm64/boot/dts/mediatek/Makefile
>> index af362a085a02..72fd683c9264 100644
>> --- a/arch/arm64/boot/dts/mediatek/Makefile
>> +++ b/arch/arm64/boot/dts/mediatek/Makefile
>> @@ -3,6 +3,7 @@ dtb-$(CONFIG_ARCH_MEDIATEK) += mt2712-evb.dtb
>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt6755-evb.dtb
>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt6779-evb.dtb
>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt6795-evb.dtb
>> +dtb-$(CONFIG_ARCH_MEDIATEK) += mt6795-sony-xperia-m5.dtb
> -holly.dtb?
> 

I prefer using the commercial name to identify the device.
"Holly" is the smartphone project codename and that is mentioned almost nowhere:
the aim here is to enhance readability as to make it immediately understandable
that this devicetree is for the Xperia M5 device.

>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt6797-evb.dtb
>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt6797-x20-dev.dtb
>>   dtb-$(CONFIG_ARCH_MEDIATEK) += mt7622-rfb1.dtb
>> diff --git a/arch/arm64/boot/dts/mediatek/mt6795-sony-xperia-m5.dts b/arch/arm64/boot/dts/mediatek/mt6795-sony-xperia-m5.dts
>> new file mode 100644
>> index 000000000000..94d011c4126c
>> --- /dev/null
>> +++ b/arch/arm64/boot/dts/mediatek/mt6795-sony-xperia-m5.dts
>> @@ -0,0 +1,90 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2022, Collabora Ltd
>> + * Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
>> + */
>> +
>> +/dts-v1/;
>> +#include "mt6795.dtsi"
>> +
>> +#include <dt-bindings/gpio/gpio.h>
> Looks unused.
> 

Right, I'll remove that in v2.

>> +
>> +/ {
>> +	model = "Sony Xperia M5";
>> +	compatible = "sony,xperia-m5", "mediatek,mt6795";
> sony,holly?
> 

I'm sorry, but I can't understand the sense of adding that compatible string to
the mix. To the kernel, it doesn't mean anything - and we already have another
string advertising the specific machine, which is "sony,xperia-m5".

Of course, there is no Xperia M5 with a different SoC and, even if there was a
xperia-m5 with a different SoC, we anyway have both a machine compatible and a
SoC compatible in here, so that would still not pose any issue.

>> +	chassis-type = "handset";
>> +
>> +	aliases {
>> +		mmc0 = &mmc0;
>> +		mmc1 = &mmc1;
>> +		serial0 = &uart0;
>> +		serial1 = &uart1;
>> +	};
>> +
>> +	memory@40000000 {
>> +		device_type = "memory";
>> +		reg = <0 0x40000000 0 0x1E800000>;
> Lowercase hex in size. Also, doesn't the bootloader fill it in?
> 

Updating the device to the latest software version will give you a bootloader
that fills that in, but the first-ever software release contains one that will
not do that in particular conditions (fastboot boot).

>> +	};
>> +
>> +	reserved_memory: reserved-memory {
>> +		#address-cells = <2>;
>> +		#size-cells = <2>;
>> +		ranges;
>> +
>> +		/* 128 KiB reserved for ARM Trusted Firmware (BL31) */
> Is that true for all devices with this SoC, or..? If so, it may be worth
> moving this into mt6795.dtsi.
> 
>> +		bl31_secmon_reserved: secmon@43000000 {
> memory@, everywhere. Use labels to name the nodes.
> 

I'm afraid that's not possible, as the bootloader is reading the devicetree
and requires these nodes to follow this naming.

>> +			no-map;
> reg goes first.

Will fix in v2.

Best regards,
Angelo