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Wed, 3 May 2023 17:03:10 GMT Received: from hu-mojha-hyd.qualcomm.com (10.80.80.8) by nasanex01c.na.qualcomm.com (10.45.79.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.42; Wed, 3 May 2023 10:03:04 -0700 From: Mukesh Ojha To: , , , , , , , , , , , , , CC: , , , , , , "Mukesh Ojha" Subject: [PATCH v3 03/18] docs: qcom: Add qualcomm minidump guide Date: Wed, 3 May 2023 22:32:17 +0530 Message-ID: <1683133352-10046-4-git-send-email-quic_mojha@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1683133352-10046-1-git-send-email-quic_mojha@quicinc.com> References: <1683133352-10046-1-git-send-email-quic_mojha@quicinc.com> MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nasanex01c.na.qualcomm.com (10.45.79.139) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: V6yj7ZJP8E4f1rkmRHy-wa5R9HkPvFjT X-Proofpoint-GUID: V6yj7ZJP8E4f1rkmRHy-wa5R9HkPvFjT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-03_12,2023-05-03_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 impostorscore=0 adultscore=0 mlxlogscore=999 spamscore=0 phishscore=0 clxscore=1015 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303200000 definitions=main-2305030145 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230503_100330_974492_65617A3A X-CRM114-Status: GOOD ( 33.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add the qualcomm minidump guide for the users which tries to cover the dependency and the way to test and collect minidump on Qualcomm supported platforms. Signed-off-by: Mukesh Ojha --- Documentation/admin-guide/qcom_minidump.rst | 246 ++++++++++++++++++++++++++++ 1 file changed, 246 insertions(+) create mode 100644 Documentation/admin-guide/qcom_minidump.rst diff --git a/Documentation/admin-guide/qcom_minidump.rst b/Documentation/admin-guide/qcom_minidump.rst new file mode 100644 index 0000000..062c797 --- /dev/null +++ b/Documentation/admin-guide/qcom_minidump.rst @@ -0,0 +1,246 @@ +Qualcomm Minidump Feature +========================= + +Introduction +------------ + +Minidump is a best effort mechanism to collect useful and predefined +data for first level of debugging on end user devices running on +Qualcomm SoCs. It is built on the premise that System on Chip (SoC) +or subsystem part of SoC crashes, due to a range of hardware and +software bugs. Hence, the ability to collect accurate data is only +a best-effort. The data collected could be invalid or corrupted, data +collection itself could fail, and so on. + +Qualcomm devices in engineering mode provides a mechanism for generating +full system ramdumps for post mortem debugging. But in some cases it's +however not feasible to capture the entire content of RAM. The minidump +mechanism provides the means for selecting region should be included in +the ramdump. + +:: + + +-----------------------------------------------+ + | DDR +-------------+ | + | | SS0-ToC| | + | +----------------+ +----------------+ | | + | |Shared memory | | SS1-ToC| | | + | |(SMEM) | | | | | + | | | +-->|--------+ | | | + | |G-ToC | | | SS-ToC \ | | | + | |+-------------+ | | | +-----------+ | | | + | ||-------------| | | | |-----------| | | | + | || SS0-ToC | | | +-|<|SS1 region1| | | | + | ||-------------| | | | | |-----------| | | | + | || SS1-ToC |-|>+ | | |SS1 region2| | | | + | ||-------------| | | | |-----------| | | | + | || SS2-ToC | | | | | ... | | | | + | ||-------------| | | | |-----------| | | | + | || ... | | |-|<|SS1 regionN| | | | + | ||-------------| | | | |-----------| | | | + | || SSn-ToC | | | | +-----------+ | | | + | |+-------------+ | | | | | | + | | | | |----------------| | | + | | | +>| regionN | | | + | | | | |----------------| | | + | +----------------+ | | | | | + | | |----------------| | | + | +>| region1 | | | + | |----------------| | | + | | | | | + | |----------------|-+ | + | | region5 | | + | |----------------| | + | | | | + | Region information +----------------+ | + | +---------------+ | + | |region name | | + | |---------------| | + | |region address | | + | |---------------| | + | |region size | | + | +---------------+ | + +-----------------------------------------------+ + G-ToC: Global table of content + SS-ToC: Subsystem table of content + SS0-SSn: Subsystem numbered from 0 to n + +The core of minidump feature is part of Qualcomm's boot firmware code. +It initializes shared memory(SMEM), which is a part of DDR and +allocates a small section of it to minidump table i.e also called +global table of content (G-ToC). Each subsystem (APSS, ADSP, ...) has +their own table of segments to be included in the minidump, all +references from a descriptor in SMEM (G-ToC). Each segment/region has +some details like name, physical address and it's size etc. and it +could be anywhere scattered in the DDR. + +Minidump kernel driver concept +------------------------------ + +Qualcomm minidump kernel driver adds the capability to add linux region +to be dumped as part of ram dump collection. At the moment, shared memory +driver creates plaform device for minidump driver and give a means to +APSS minidump to initialize itself on probe. + +This driver provides ``qcom_apss_minidump_region_register`` and +``qcom_apss_minidump_region_unregister`` API's to register and unregister +apss minidump region. It also gives a mechanism to update physical/virtual +address for the client whose addresses keeps on changing e.g Current stack +address of task keep on changing on context switch for each core. So these +clients can update their addresses with ``qcom_apss_minidump_update_region`` +API. + +The driver also supports registration for the clients who came before +minidump driver was initialized. It maintains pending list of clients +who came before minidump and once minidump is initialized it registers +them in one go. + +To simplify post mortem debugging, driver creates and maintain an ELF +header as first region that gets updated each time a new region gets +registered. + +The solution supports extracting the ramdump/minidump produced either +over USB or stored to an attached storage device. + +Dependency of minidump kernel driver +------------------------------------ + +It is to note that whole of minidump thing depends on Qualcomm boot +firmware whether it supports minidump or not. So, if the minidump +smem id is present in shared memory, it indicates that minidump +is supported from boot firmware and it is possible to dump linux +(APSS) region as part of minidump collection. + +How a kernel client driver can register region with minidump +------------------------------------------------------------ + +Client driver can use ``qcom_apss_minidump_region_register`` API's to +register and ``qcom_apss_minidump_region_unregister`` to unregister +their region from minidump driver. + +Client need to fill their region by filling qcom_apss_minidump_region +structure object which consist of the region name, region's +virtual and physical address and its size. + +Below is one sample client driver snippet which try to allocate +a region from kernel heap of certain size and it writes a certain +known pattern (that can help in verification after collection +that we got the exact pattern, what we wrote) and registers it with +minidump. + + .. code-block:: c + + #include + [...] + + + [... inside a function ...] + struct qcom_apss_minidump_region region; + + [...] + + client_mem_region = kzalloc(region_size, GFP_KERNEL); + if (!client_mem_region) + return -ENOMEM; + + [... Just write a pattern ...] + memset(client_mem_region, 0xAB, region_size); + + [... Fill up the region object ...] + strlcpy(region.name, "REGION_A", sizeof(region.name)); + region.virt_addr = client_mem_region; + region.phys_addr = virt_to_phys(client_mem_region); + region.size = region_size; + + ret = qcom_apss_minidump_region_register(®ion); + if (ret < 0) { + pr_err("failed to add region in minidump: err: %d\n", ret); + return ret; + } + + [...] + + +Test +---- + +Existing Qualcomm devices already supports entire ddr dump (also called +full dump) by writing appropriate value to Qualcomm's top control and +status register(tcsr) in driver/firmware/qcom_scm.c . + +SCM device Tree bindings required to support download mode +For example (sm8450) :: + + / { + + [...] + + firmware { + scm: scm { + compatible = "qcom,scm-sm8450", "qcom,scm"; + [... tcsr register ... ] + qcom,dload-mode = <&tcsr 0x13000>; + + [...] + }; + }; + + [...] + + soc: soc@0 { + + [...] + + tcsr: syscon@1fc0000 { + compatible = "qcom,sm8450-tcsr", "syscon"; + reg = <0x0 0x1fc0000 0x0 0x30000>; + }; + + [...] + }; + [...] + + }; + +User of minidump can pass qcom_scm.download_mode="mini" to kernel +commandline to set the current download mode to minidump. +Similarly, "full" is passed to set the download mode to full dump +where entire ddr dump will be collected while setting it "full,mini" +will collect minidump along with fulldump. + +Writing to sysfs node can also be used to set the mode to minidump. + +:: + echo "mini" > /sys/module/qcom_scm/parameter/download_mode + +Once the download mode is set, any kind of crash will make the device collect +respective dump as per set download mode. + +Dump collection +--------------- + +The solution supports extracting the minidump produced either over USB or +stored to an attached storage device. + +By default, dumps are downloaded via USB to the attached x86_64 machine +running PCAT (Qualcomm tool) software. Upon download, we will see +a set of binary blobs starts with name md_* in PCAT configured directory +in x86_64 machine, so for above example from the client it will be +md_REGION_A.BIN. This binary blob depends on region content to determine +whether it needs external parser support to get the content of the region, +so for simple plain ASCII text we don't need any parsing and the content +can be seen just opening the binary file. + +To collect the dump to attached storage type, one need to write appropriate +value to IMEM register, in that case dumps are collected in rawdump +partition on the target device itself. + +One need to read the entire rawdump partition and pull out content to +save it onto the attached x86_64 machine over USB. Later, this rawdump +can be pass it to another tool dexter.exe(Qualcomm tool) which converts +this into the similar binary blobs which we have got it when download type +was set to USB i.e a set of registered region as blobs and their name +starts with md_*. + +Replacing the dexter.exe with some open source tool can be added as future +scope of this document.