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([2a01:e0a:106d:1080:73bc:1eca:d39e:509]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4851fafe4c9sm47514905e9.15.2026.03.05.03.35.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Mar 2026 03:35:52 -0800 (PST) Message-ID: <278f5018-9183-4eeb-bde1-7c19adecab06@linaro.org> Date: Thu, 5 Mar 2026 12:35:52 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: Neil Armstrong Subject: Re: [PATCH RFC v4 1/4] media: dt-bindings: Add Amlogic V4L2 video decoder To: Krzysztof Kozlowski , Zhentao Guo , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Kevin Hilman , Jerome Brunet , Martin Blumenstingl Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org References: <20260213-b4-s4-vdec-upstream-v4-0-c7112d00d662@amlogic.com> <20260213-b4-s4-vdec-upstream-v4-1-c7112d00d662@amlogic.com> <75e55ceb-e6dd-47b5-a829-66f6fbb3e13e@amlogic.com> <2f68ee18-e9d9-4da6-900c-93a7663b3c9d@kernel.org> <598c161c-d157-40e5-992c-912540589d7e@amlogic.com> <58d57a6c-7c69-4f5b-a4c2-f34ef0238511@kernel.org> <26d0f52e-3681-46ce-b0dc-0cb020e8d9a1@amlogic.com> <69900d76-3820-467a-9fbc-13f79189df2f@kernel.org> Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: <69900d76-3820-467a-9fbc-13f79189df2f@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/5/26 12:08, Krzysztof Kozlowski wrote: > On 05/03/2026 12:01, Zhentao Guo wrote: >> >> 2. Why canvas is needed? >> >> 1. Since the ARM IOMMU HW is not integrated into the Amlogic SOCs,we >> need canvas to prevent the DDR memory used by the decoder from being >> rewrote by other hardware. Canvas provides the decoder with a >> configurable DDR memory range, as well as hardware-based detection >> and blocking for out-of-bounds access. >> 2. From the diagram above, we can see a lite CPU called AMRISC. AMRISC >> is the controller of the decoder HW and the decoder driver needs to >> access the decoder hardware through AMRISC. However, AMRISC is a >> 16-bit CPU and cannot directly handle 32-bit or 64-bit physical >> addresses. Therefore, canvas is required to convert the addresses >> into index to facilitate processing by the AMRISC core. > > This suggests "Canvas" is IOMMU, thus use proper IOMMU abstractions and > you cannot have own phandle for it. No it is not, canvas was used for a long time for the display and video processing side. It's absolutely not like an IOMMU, the diagram is quite clear. Neil > > Best regards, > Krzysztof