Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 7/8] arm64: dts: allwinner: Add Allwinner H616 .dtsi file
To:     Samuel Holland <samuel@sholland.org>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@siol.net>
Cc:     devicetree@vger.kernel.org,
        Linus Walleij <linus.walleij@linaro.org>,
        linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com,
        Rob Herring <robh+dt@kernel.org>,
        Icenowy Zheng <icenowy@aosc.xyz>,
        Yangtao Li <frank@allwinnertech.com>,
        linux-arm-kernel@lists.infradead.org
References: <20201202135409.13683-1-andre.przywara@arm.com>
 <20201202135409.13683-8-andre.przywara@arm.com>
 <3b4f4bf6-2fba-5d35-bdf5-74b8ced10357@sholland.org>
From:   =?UTF-8?Q?Andr=c3=a9_Przywara?= <andre.przywara@arm.com>
Autocrypt: addr=andre.przywara@arm.com; prefer-encrypt=mutual; keydata=
 xsFNBFNPCKMBEAC+6GVcuP9ri8r+gg2fHZDedOmFRZPtcrMMF2Cx6KrTUT0YEISsqPoJTKld
 tPfEG0KnRL9CWvftyHseWTnU2Gi7hKNwhRkC0oBL5Er2hhNpoi8x4VcsxQ6bHG5/dA7ctvL6
 kYvKAZw4X2Y3GTbAZIOLf+leNPiF9175S8pvqMPi0qu67RWZD5H/uT/TfLpvmmOlRzNiXMBm
 kGvewkBpL3R2clHquv7pB6KLoY3uvjFhZfEedqSqTwBVu/JVZZO7tvYCJPfyY5JG9+BjPmr+
 REe2gS6w/4DJ4D8oMWKoY3r6ZpHx3YS2hWZFUYiCYovPxfj5+bOr78sg3JleEd0OB0yYtzTT
 esiNlQpCo0oOevwHR+jUiaZevM4xCyt23L2G+euzdRsUZcK/M6qYf41Dy6Afqa+PxgMEiDto
 ITEH3Dv+zfzwdeqCuNU0VOGrQZs/vrKOUmU/QDlYL7G8OIg5Ekheq4N+Ay+3EYCROXkstQnf
 YYxRn5F1oeVeqoh1LgGH7YN9H9LeIajwBD8OgiZDVsmb67DdF6EQtklH0ycBcVodG1zTCfqM
 AavYMfhldNMBg4vaLh0cJ/3ZXZNIyDlV372GmxSJJiidxDm7E1PkgdfCnHk+pD8YeITmSNyb
 7qeU08Hqqh4ui8SSeUp7+yie9zBhJB5vVBJoO5D0MikZAODIDwARAQABzS1BbmRyZSBQcnp5
 d2FyYSAoQVJNKSA8YW5kcmUucHJ6eXdhcmFAYXJtLmNvbT7CwXsEEwECACUCGwMGCwkIBwMC
 BhUIAgkKCwQWAgMBAh4BAheABQJTWSV8AhkBAAoJEAL1yD+ydue63REP/1tPqTo/f6StS00g
 NTUpjgVqxgsPWYWwSLkgkaUZn2z9Edv86BLpqTY8OBQZ19EUwfNehcnvR+Olw+7wxNnatyxo
 D2FG0paTia1SjxaJ8Nx3e85jy6l7N2AQrTCFCtFN9lp8Pc0LVBpSbjmP+Peh5Mi7gtCBNkpz
 KShEaJE25a/+rnIrIXzJHrsbC2GwcssAF3bd03iU41J1gMTalB6HCtQUwgqSsbG8MsR/IwHW
 XruOnVp0GQRJwlw07e9T3PKTLj3LWsAPe0LHm5W1Q+euoCLsZfYwr7phQ19HAxSCu8hzp43u
 zSw0+sEQsO+9wz2nGDgQCGepCcJR1lygVn2zwRTQKbq7Hjs+IWZ0gN2nDajScuR1RsxTE4WR
 lj0+Ne6VrAmPiW6QqRhliDO+e82riI75ywSWrJb9TQw0+UkIQ2DlNr0u0TwCUTcQNN6aKnru
 ouVt3qoRlcD5MuRhLH+ttAcmNITMg7GQ6RQajWrSKuKFrt6iuDbjgO2cnaTrLbNBBKPTG4oF
 D6kX8Zea0KvVBagBsaC1CDTDQQMxYBPDBSlqYCb/b2x7KHTvTAHUBSsBRL6MKz8wwruDodTM
 4E4ToV9URl4aE/msBZ4GLTtEmUHBh4/AYwk6ACYByYKyx5r3PDG0iHnJ8bV0OeyQ9ujfgBBP
 B2t4oASNnIOeGEEcQ2rjzsFNBFNPCKMBEACm7Xqafb1Dp1nDl06aw/3O9ixWsGMv1Uhfd2B6
 it6wh1HDCn9HpekgouR2HLMvdd3Y//GG89irEasjzENZPsK82PS0bvkxxIHRFm0pikF4ljIb
 6tca2sxFr/H7CCtWYZjZzPgnOPtnagN0qVVyEM7L5f7KjGb1/o5EDkVR2SVSSjrlmNdTL2Rd
 zaPqrBoxuR/y/n856deWqS1ZssOpqwKhxT1IVlF6S47CjFJ3+fiHNjkljLfxzDyQXwXCNoZn
 BKcW9PvAMf6W1DGASoXtsMg4HHzZ5fW+vnjzvWiC4pXrcP7Ivfxx5pB+nGiOfOY+/VSUlW/9
 GdzPlOIc1bGyKc6tGREH5lErmeoJZ5k7E9cMJx+xzuDItvnZbf6RuH5fg3QsljQy8jLlr4S6
 8YwxlObySJ5K+suPRzZOG2+kq77RJVqAgZXp3Zdvdaov4a5J3H8pxzjj0yZ2JZlndM4X7Msr
 P5tfxy1WvV4Km6QeFAsjcF5gM+wWl+mf2qrlp3dRwniG1vkLsnQugQ4oNUrx0ahwOSm9p6kM
 CIiTITo+W7O9KEE9XCb4vV0ejmLlgdDV8ASVUekeTJkmRIBnz0fa4pa1vbtZoi6/LlIdAEEt
 PY6p3hgkLLtr2GRodOW/Y3vPRd9+rJHq/tLIfwc58ZhQKmRcgrhtlnuTGTmyUqGSiMNfpwAR
 AQABwsFfBBgBAgAJBQJTTwijAhsMAAoJEAL1yD+ydue64BgP/33QKczgAvSdj9XTC14wZCGE
 U8ygZwkkyNf021iNMj+o0dpLU48PIhHIMTXlM2aiiZlPWgKVlDRjlYuc9EZqGgbOOuR/pNYA
 JX9vaqszyE34JzXBL9DBKUuAui8z8GcxRcz49/xtzzP0kH3OQbBIqZWuMRxKEpRptRT0wzBL
 O31ygf4FRxs68jvPCuZjTGKELIo656/Hmk17cmjoBAJK7JHfqdGkDXk5tneeHCkB411p9WJU
 vMO2EqsHjobjuFm89hI0pSxlUoiTL0Nuk9Edemjw70W4anGNyaQtBq+qu1RdjUPBvoJec7y/
 EXJtoGxq9Y+tmm22xwApSiIOyMwUi9A1iLjQLmngLeUdsHyrEWTbEYHd2sAM2sqKoZRyBDSv
 ejRvZD6zwkY/9nRqXt02H1quVOP42xlkwOQU6gxm93o/bxd7S5tEA359Sli5gZRaucpNQkwd
 KLQdCvFdksD270r4jU/rwR2R/Ubi+txfy0dk2wGBjl1xpSf0Lbl/KMR5TQntELfLR4etizLq
 Xpd2byn96Ivi8C8u9zJruXTueHH8vt7gJ1oax3yKRGU5o2eipCRiKZ0s/T7fvkdq+8beg9ku
 fDO4SAgJMIl6H5awliCY2zQvLHysS/Wb8QuB09hmhLZ4AifdHyF1J5qeePEhgTA+BaUbiUZf
 i4aIXCH3Wv6K
Organization: ARM Ltd.
Message-ID: <34e5618e-4a3d-9a46-5077-179c82592fce@arm.com>
Date:   Thu, 3 Dec 2020 10:53:54 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.12.0
MIME-Version: 1.0
In-Reply-To: <3b4f4bf6-2fba-5d35-bdf5-74b8ced10357@sholland.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-GB
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 03/12/2020 03:16, Samuel Holland wrote:

Hi,

> On 12/2/20 7:54 AM, Andre Przywara wrote:
> ...
>> +	soc {
>> +		compatible = "simple-bus";
>> +		#address-cells = <1>;
>> +		#size-cells = <1>;
>> +		ranges = <0x0 0x0 0x0 0x40000000>;
>> +
>> +		syscon: syscon@3000000 {
>> +			compatible = "allwinner,sun50i-h616-system-control",
>> +				     "allwinner,sun50i-a64-system-control";
>> +			reg = <0x03000000 0x1000>;
>> +			#address-cells = <1>;
>> +			#size-cells = <1>;
>> +			ranges;
>> +
>> +			sram_c: sram@28000 {
>> +				compatible = "mmio-sram";
>> +				reg = <0x00028000 0x30000>;
>> +				#address-cells = <1>;
>> +				#size-cells = <1>;
>> +				ranges = <0 0x00028000 0x30000>;
>> +			};
>> +
>> +			sram_c1: sram@1a00000 {
>> +				compatible = "mmio-sram";
>> +				reg = <0x01a00000 0x200000>;
>> +				#address-cells = <1>;
>> +				#size-cells = <1>;
>> +				ranges = <0 0x01a00000 0x200000>;
>> +
>> +				ve_sram: sram-section@0 {
>> +					compatible = "allwinner,sun50i-h616-sram-c1",
>> +						     "allwinner,sun4i-a10-sram-c1";
>> +					reg = <0x000000 0x200000>;
>> +				};
>> +			};
>> +		};
> 
> You mentioned that you could not find a SRAM A2. How were these SRAM ranges
> verified? If you can load eGON.BT0 larger than 32 KiB, then presumably NBROM
> uses SRAM C, and it is in the manual, but I see no mention of SRAM C1.

The manual says that SRAM C *can* be used by "the system", at boot time,
as long as it's configured correctly. I couldn't find any details on how
to switch clock sources for SRAM C, and the manual stanza on this is
quite gibberish. I presume it's configured either by BROM or by reset
default this way. I think the idea is that the later users (VE, DE) take
ownership at some point (which means we can't run any firmware in there).
The BSP boot0 is 48KB already, so reaching into SRAM C, and the code
itself heavily uses SRAM C (found by hacking boot0 to drop to FEL and
inspecting the memory afterwards).

For C1: I copied this name from the H6 .dtsi, the manual calls this
"VE-SRAM", in both manuals, and the description looks identical there
for both SoCs. I think this will be later used by the video engine, so I
kept it in. The large size made me suspicious, and from former
experiments it looks like being aliased to (parts of) SRAM C.

Maybe some guys with more VE knowledge can shine some light on this?

Cheers,
Andre