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Tue, 14 Apr 2026 02:56:52 -0700 (PDT) X-Received: by 2002:a05:6a00:ad8d:b0:82f:316:3208 with SMTP id d2e1a72fcca58-82f0c35628bmr16502526b3a.29.1776160612161; Tue, 14 Apr 2026 02:56:52 -0700 (PDT) Received: from [10.217.219.169] ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f0c30ee4bsm15060311b3a.2.2026.04.14.02.56.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Apr 2026 02:56:51 -0700 (PDT) Message-ID: <8f620562-2e1e-4d61-a823-767fbe51828a@oss.qualcomm.com> Date: Tue, 14 Apr 2026 15:26:47 +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 v4 8/9] bus: mhi: Expose DDR training data via controller sysfs To: Manivannan Sadhasivam Cc: Jonathan Corbet , Shuah Khan , Jeff Hugo , Carl Vanderlip , Oded Gabbay , andersson@kernel.org, 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: <20260319-sahara_protocol_new_v2-v4-0-47ad79308762@oss.qualcomm.com> <20260319-sahara_protocol_new_v2-v4-8-47ad79308762@oss.qualcomm.com> Content-Language: en-US From: Kishore Batta In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE0MDA5MiBTYWx0ZWRfXzbdSvc2ne0Un d7Jzx44uh0d8AlGyHLtmutsFLLKKlJUggdipOG8ZHvThZVdL/fHCtSbIqejctKzd5rdh/y1CQnF vM4i8jzU3Z6AM+RabDSESgMLKkY6VCY4JVPVBnbRgLXPMyToZDQh3b3g3BEjDhswD9OyHdLHSKx xVIC3LAHdj802UM01kWEoR67pzYpf+i9ZW9EUVso/5oBOCykztgv0G3SUfS5npb6u13O8esUqhA V9SP5/MJ/lWKD1VhbVmnL52K0V/qZ8aX9j5Hw+8aAv0HyFxwtZLoj3/VGnk44ad8JPk67+ceMM1 JluXGs/59UDrwYW/aAWc8uUxl40Dbo2CbOwA4lm77ZpXXMnpP3iUr4T/acU2zotm0dDf5wUujAy dFvFjjBSjYdkWu9xnxQZErUUc4mWiAxygMpddyAcmsUqclCb/a/6KdtheQWlt2DWlkQGbKeDIVF jQf2YxseNPoPevhlXuw== X-Proofpoint-ORIG-GUID: APUxvJbEKe589rlWWd_bK9uPPK83NMJu X-Authority-Analysis: v=2.4 cv=Iowutr/g c=1 sm=1 tr=0 ts=69de0f65 cx=c_pps a=oF/VQ+ItUULfLr/lQ2/icg==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=EUspDBNiAAAA:8 a=7NWoxAv4aW94f8snxxYA:9 a=QEXdDO2ut3YA:10 a=3WC7DwWrALyhR5TkjVHa:22 X-Proofpoint-GUID: APUxvJbEKe589rlWWd_bK9uPPK83NMJu 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=2026-04-14_02,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 bulkscore=0 spamscore=0 phishscore=0 clxscore=1015 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604140092 On 4/13/2026 5:28 PM, Manivannan Sadhasivam wrote: > On Thu, Mar 19, 2026 at 12:01:48PM +0530, Kishore Batta wrote: >> DDR training data captured during Sahara command mode needs to be >> accessible to userspace so it can be persisted and reused on subsequent >> boots. Currently, the training data is stored internally in the driver >> but has no external visibility once the sahara channel is torn down. >> > Maybe share some steps on how the userspace is expected to use this calibration > data. Sure. will update the commit message with the required details in the next version. >> Expose the captured DDR training data via a read-only binary sysfs >> attribute on the MHI controller device. The sysfs file is created under >> the controller node, allowing userspace to read the training data even >> after the sahara channel device has been removed. >> > So once the calibration data is read, how it can be used further? The userspace will store the calibration data in "mdmddr_0x.mbn format. In the next boot, Sahara driver loads the real DDR calibration data and training data will be restored. No repeated DDR training is performed at target end. > >> The sysfs attribute reads directly from controller-scoped storage and >> relies on device managed resources for cleanup when the controller >> device is destroyed. No explicit sysfs removal is required, avoiding >> lifetime dependencies on the Sahara channel device. >> > Missing ABI documentation. > > - Mani Currently i have added in a separate patch(9/9). I will squash it with this patch in the next version. >> Signed-off-by: Kishore Batta >> --- >> drivers/bus/mhi/sahara/sahara.c | 69 +++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 69 insertions(+) >> >> diff --git a/drivers/bus/mhi/sahara/sahara.c b/drivers/bus/mhi/sahara/sahara.c >> index c88f1220199ac4373d3552167870c19a0d5f23b9..b7208738df10fc3c3895acd46873412818dc1730 100644 >> --- a/drivers/bus/mhi/sahara/sahara.c >> +++ b/drivers/bus/mhi/sahara/sahara.c >> @@ -415,6 +415,73 @@ static struct sahara_ctrl_trng_data *sahara_ctrl_trng_get(struct device *dev) >> return ct; >> } >> >> +static ssize_t ddr_training_data_read(struct file *filp, struct kobject *kobj, >> + const struct bin_attribute *attr, char *buf, >> + loff_t offset, size_t count) >> +{ >> + struct device *dev = kobj_to_dev(kobj); >> + struct sahara_ctrl_trng_data *ct; >> + size_t available; >> + >> + ct = sahara_ctrl_trng_get(dev); >> + if (!ct) >> + return -ENODEV; >> + >> + mutex_lock(&ct->lock); >> + >> + /* No data yet or offset past end */ >> + if (!ct->data || offset >= ct->size) { >> + mutex_unlock(&ct->lock); >> + return 0; >> + } >> + >> + available = ct->size - offset; >> + count = min(count, available); >> + memcpy(buf, (u8 *)ct->data + offset, count); >> + >> + mutex_unlock(&ct->lock); >> + >> + return count; >> +} >> + >> +static const struct bin_attribute ddr_training_data_attr = { >> + .attr = { >> + .name = "ddr_training_data", >> + .mode = 0444, >> + }, >> + .read = ddr_training_data_read, >> +}; >> + >> +static void sahara_sysfs_devres_release(struct device *dev, void *res) >> +{ >> + device_remove_bin_file(dev, &ddr_training_data_attr); >> +} >> + >> +static void sahara_sysfs_create(struct mhi_device *mhi_dev) >> +{ >> + struct device *dev = &mhi_dev->mhi_cntrl->mhi_dev->dev; >> + void *cookie; >> + int ret; >> + >> + if (devres_find(dev, sahara_sysfs_devres_release, NULL, NULL)) >> + return; >> + >> + ret = device_create_bin_file(dev, &ddr_training_data_attr); >> + if (ret) { >> + dev_warn(&mhi_dev->dev, >> + "Failed to create DDR training sysfs node (%d)\n", ret); >> + return; >> + } >> + >> + cookie = devres_alloc(sahara_sysfs_devres_release, 1, GFP_KERNEL); >> + if (!cookie) { >> + device_remove_bin_file(dev, &ddr_training_data_attr); >> + return; >> + } >> + >> + devres_add(dev, cookie); >> +} >> + >> static int sahara_find_image(struct sahara_context *context, u32 image_id) >> { >> char *fw_path; >> @@ -1272,6 +1339,8 @@ static int sahara_mhi_probe(struct mhi_device *mhi_dev, const struct mhi_device_ >> return ret; >> } >> >> + sahara_sysfs_create(mhi_dev); >> + >> return 0; >> } >> >> >> -- >> 2.34.1 >>