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Mon, 13 Jul 2026 00:20:05 -0700 (PDT) X-Received: by 2002:a17:90b:4c02:b0:37f:e326:6557 with SMTP id 98e67ed59e1d1-38dc74c4b29mr7787302a91.4.1783927205229; Mon, 13 Jul 2026 00:20:05 -0700 (PDT) Received: from [10.217.219.169] ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38a583a16c2sm6071162a91.13.2026.07.13.00.20.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Jul 2026 00:20:04 -0700 (PDT) Message-ID: <05af9d4f-ac6a-4a7d-bb7a-41fd50fc9935@oss.qualcomm.com> Date: Mon, 13 Jul 2026 12:50:00 +0530 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: [PATCH v6 1/7] Add documentation for Sahara protocol To: Randy Dunlap , Jonathan Corbet , Shuah Khan , Jeff Hugo , Carl Vanderlip , Oded Gabbay , Manivannan Sadhasivam Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, mhi@lists.linux.dev References: <20260701-sahara_protocol_new_v2-v6-0-3a78362c4741@oss.qualcomm.com> <20260701-sahara_protocol_new_v2-v6-1-3a78362c4741@oss.qualcomm.com> <699644e7-2fc2-41b5-9e02-7f4dbc2aa3a7@infradead.org> Content-Language: en-US From: Kishore Batta In-Reply-To: <699644e7-2fc2-41b5-9e02-7f4dbc2aa3a7@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Info: AW1haW4tMjYwNzEzMDA3NCBTYWx0ZWRfX7leVyXR369gv F3dZQRMAC0Umb4QrNNHllkvqcZoEguYnw+uYPRf4C36FuFMUcDa5/nmOeAxfHZ/l1q3hfCjDHN4 xx5NAtj/rBgF1bZ+7iUVP8oxiNGkvBc= X-Proofpoint-ORIG-GUID: WqOcR5u0wrdZYyde4tSDKBFjGt0nVPuo X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzEzMDA3NCBTYWx0ZWRfX4GjLEKTIWbbF 7S7BZ4WQMpqRTSNx5VIkf916PsQaiaXDb0uztDguE1QYf2A8CI6C8kb/YEnpIUlByyJuDsUHKSj WVMwSgoi8BbpaEL0RCJ42TBwntwl5UKlDbNoI/UaYb1Z3FGc28pST/9dlCS0kveHY2rGU2wxMOT 9K9rIoivNe3VV8yg/Pmc6jGDtsgMwEtRfqxJVnFUbg0r3duNOrmgL/NZhjse1d+YGRoxo4nVyz1 yWgcz+DS5l1/WBSaRAl/AVF9tUZ5mgp086pa42bji1141zI1jCIk97GSB2paKgnXb3CmkjYoLXr lYGxHq96gaHVolH+MP1gPXxxNUxz24hVeIpREoi2wYjjWNEFwzetRfPecFOGiaaAAzTPyGkJ5lb 4bFPN+cULBfkoj3RNu87TleTIPyb7eZLdF1Ii4ibsEcQsMPoNGG8bnhe4RCJ+wKZZ6eycJx/HiO L2k1SXYYi9CeTG0DLSA== X-Proofpoint-GUID: WqOcR5u0wrdZYyde4tSDKBFjGt0nVPuo X-Authority-Analysis: v=2.4 cv=KM9qylFo c=1 sm=1 tr=0 ts=6a5491a6 cx=c_pps a=RP+M6JBNLl+fLTcSJhASfg==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=s-wG5dvStlP9jbJ101gA:9 a=QEXdDO2ut3YA:10 a=iS9zxrgQBfv6-_F4QbHw:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-13_02,2026-07-10_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 phishscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 adultscore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607130074 On 7/8/2026 10:16 AM, Randy Dunlap wrote: > On 7/1/26 3:37 AM, Kishore Batta wrote: >> +The packet flow sequence is as follows : >> + >> +1. The target sends the hello packet to the host to initiate the protocol >> + with the mode set to image transfer pending. >> + >> +2. The host sends a hello response packet with a success status and sets the >> + mode to image transfer pending after it receives the hello packet and >> + validates the protocol version running on the target. >> + >> +3. After the target receives the hello response, it initiates the data >> + transfer by requesting the size of DDR training/calibration data. >> + >> +4. The host sends back the DDR training/calibration data to the target. >> + >> +5. The target decodes the training data and does not find valid DDR >> + calibration data, target sends END_IMAGE_TX to interrupt the transfer. >> + >> +6. The host sends DONE after receives END_IMAGE_TX. >> + >> +7. The target sends DONE_RESP with mode = IMAGE_TX_PENDING because it has >> + not received all images. >> + >> +8. The target executes DDR training process to generate valid DDR calibration >> + data and prepares to push back to host. >> + >> +9. The target initiates protocol by sending a hello packet with COMMAND_MODE >> + to the host. >> + >> +10. The host sends a hello response packet with a success status and sets the >> + mode to COMMAND_MODE. >> + >> +11. The target sends CMD_READY to the host. >> + >> +12. The host receives CMD_READY and starts to get command IDs to be executed. >> + >> +13. The target sends CMD_ID = 9 to push DDR calibration data to host. >> + >> +14. The host executes CMD_ID = 9 to get DDR calibration data from the target. >> + >> +15. The target sends RAW_DATA with the payload which contains DDR calibration >> + data to host. >> + >> +16. The host saves training data in the kernel buffer and exposes to userspace >> + via the sysfs entry. The host sends CMD_SWITCH_MODE with the mode set to >> + IMAGE_TX_PENDING to continue booting. >> + >> +17. After the target receives the CMD_SWITCH_MODE command, it sends HELLO to >> + the host with the mode set to IMAGE_TX_PENDING. The target and the host >> + repeat the packet flow for image transfer to get all booting-required >> + images. >> + >> +18. Upon successful transfer of all images, the target sends an END_IMAGE_TX >> + packet with a success status to the host. >> + >> +19. The host sends DONE after it receives END_IMAGE_TX. >> + >> +20. The target sends DONE_RESP with the mode set to IMAGE_TX_COMPLETE because >> + it has received all images. The process has been completed after the host >> + receives DONE_RESP with the mode set to IMAGE_TX_COMPLETE. >> + >> +Subsequent boot scenario with valid DDR calibration data >> +-------------------------------------------------------- >> + >> +The below firgure shows the subsequent boot scenario with valid DDR calibration >> +data process being loaded from host to target. >> + >> +.. code-block:: text >> + >> + Host Target >> + | HELLO | >> + | (mode = image transfer) | >> + |<--------------------------| >> + | | >> + | HELLO RESP | >> + | (mode = image transfer) | >> + |-------------------------->| >> + | | >> + | READ_DATA | >> + | (img ID:34, 0, offset, | >> + | size of DDR training data)| >> + |<--------------------------| >> + | | >> + | RAW_DATA | >> + |(size of DDR training data)| >> + |-------------------------->| >> + | | >> + | | >> + | END_IMAGE_TX | >> + |<--------------------------| >> + | | >> + | | >> + | DONE | >> + |-------------------------->| >> + | | >> + | | >> + | DONE_RESP | >> + | (mode = IMAGE_TX_PENDING) | >> + |<--------------------------| >> + | | >> + | Subsequent boot scenario | >> + | (valid calibration data) | >> + | DDR driver configures DDR | >> + | using valid calibration | >> + | data | >> + | | >> + | | >> + | HELLO | >> + | (mode = IMAGE_TX_PENDING) | >> + |<--------------------------| >> + | | >> + | HELLO RESP | >> + | (mode = IMAGE_TX_PENDING) | >> + |-------------------------->| >> + | | >> + | Boot/Load rest of the | >> + | images.... | >> + | | >> + | END_IMAGE_TX | >> + |<--------------------------| >> + | | >> + | | >> + | DONE | >> + |-------------------------->| >> + | | >> + | | >> + | DONE_RESP | >> + |(mode = IMAGE_TX_COMPLETE) | >> + |<--------------------------| >> + | | >> + >> +The packet flow is as follows : >> + > s/as follows :/as follows:/ > in 2 places. ACK. I'll remove the extra space before the colon in both places in the next version. > >> +1. The target sends the hello packet to the host to initiate the protocol >> + with the mode set to image transfer pending.