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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b9832f43a65sm754692866b.7.2026.03.25.02.30.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Mar 2026 02:30:54 -0700 (PDT) Message-ID: <4920d196-9002-47fa-ae92-c6f14e99c958@oss.qualcomm.com> Date: Wed, 25 Mar 2026 10:30:52 +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 Subject: Re: [RFC PATCH 2/3] media: qcom: camss: Add CAMSS Offline Processing Engine driver To: Bryan O'Donoghue , Loic Poulain Cc: vladimir.zapolskiy@linaro.org, laurent.pinchart@ideasonboard.com, kieran.bingham@ideasonboard.com, robh@kernel.org, krzk+dt@kernel.org, andersson@kernel.org, konradybcio@kernel.org, linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, johannes.goede@oss.qualcomm.com, mchehab@kernel.org References: <20260323125824.211615-1-loic.poulain@oss.qualcomm.com> <20260323125824.211615-3-loic.poulain@oss.qualcomm.com> <1ba54ec0-be51-4694-a79b-f272e76303d2@kernel.org> <12194cc0-0960-486c-be7e-1a22d95de340@kernel.org> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <12194cc0-0960-486c-be7e-1a22d95de340@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDA2NyBTYWx0ZWRfXyflKTKbep22R 2JCBkJc6kkvBB45F9XoyMu/KbG1DcjmgK95/tOe3yNQj5jYlg6Erndx1PJSpxg6+jGpf7aoLpLF cH4R13x4roWnEYyjSGYjI5GYEKV+iR34QuNznPR8w/g0BK4aFHNranT4PYBSW64ojs6XNEN/kpL 3Cg+xYESeXM+KQIaTis1yXh9Bvr7Gwjerg/c1kpJT9GoTIlju8RqrHe1Ml4NTwngOCULw+tcond YYSTjj43GwNVTu26utqrcREiQxZqWJn+lWczooHYH5AHOhqxeZy5jI7LHFE6dYLhN0YnZ/Caah5 snX6jJZlJhPb+xGePm2Vyb3TGHqAopraKxuzAfiXqNySUAo7BS78oxfojiKZQho8CJ36eQS8DEY akm29o4/mjuirMF4iElsV2Vujq7HgdLngG5uv/LIYiPpHR78iV7vlEK8IrXxJ5oh/vY5bJqbHzg txiuMdahES3q7DlkiRA== X-Authority-Analysis: v=2.4 cv=VODQXtPX c=1 sm=1 tr=0 ts=69c3ab51 cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=MAgzBORBeBVPlHHXK98A:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 X-Proofpoint-GUID: 1B43OHGkFQbM9jwzBdZ_RLMbsX5OPmnA X-Proofpoint-ORIG-GUID: 1B43OHGkFQbM9jwzBdZ_RLMbsX5OPmnA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-25_03,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 priorityscore=1501 spamscore=0 impostorscore=0 clxscore=1015 adultscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250067 On 3/24/26 12:00 PM, Bryan O'Donoghue wrote: > On 23/03/2026 15:31, Loic Poulain wrote: [...] >>> So - this is where the CDM should be used - so that you don't have to do >>> all of these MMIO writes inside of your ISR. >> Indeed, and that also the reason stripes are computed ahead of time, >> so that they can be further 'queued' in a CDM. >> >>> Is that and additional step after the RFC ? >> The current implementation (without CDM) already provides good results >> and performance, so CDM can be viewed as a future enhancement. > > That's true but then the number of MMIO writes per ISR is pretty small right now. You have about 50 writes here. > >> As far as I understand, CDM could also be implemented in a generic way >> within CAMSS, since other CAMSS blocks make use of CDM as well. >> This is something we should discuss further. > My concern is even conservatively if each module adds another 10 ? writes by the time we get to denoising, sharpening, lens shade correction, those writes could easily look more like 100. > > What user-space should submit is well documented data-structures which then get translated into CDM buffers by the OPE and IFE for the various bits of the pipeline. Would simply switching to a threaded irq handler resolve this? Konrad