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Wed, 22 Mar 2023 13:30:54 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 15.2.986.41; Wed, 22 Mar 2023 06:30:49 -0700 From: Mukesh Ojha To: , , , , , , , , CC: , , , , , , "Mukesh Ojha" Subject: [PATCH v2 3/6] docs: qcom: Add qualcomm minidump guide Date: Wed, 22 Mar 2023 19:00:14 +0530 Message-ID: <1679491817-2498-4-git-send-email-quic_mojha@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1679491817-2498-1-git-send-email-quic_mojha@quicinc.com> References: <1679491817-2498-1-git-send-email-quic_mojha@quicinc.com> MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) 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: gEgzXNIWWcCzxdI622U76Q6lInvUJxqB X-Proofpoint-GUID: gEgzXNIWWcCzxdI622U76Q6lInvUJxqB 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=2023-03-22_11,2023-03-22_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxscore=0 bulkscore=0 spamscore=0 impostorscore=0 malwarescore=0 suspectscore=0 clxscore=1015 mlxlogscore=999 adultscore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303150002 definitions=main-2303220098 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230322_063114_893983_463B9C4A X-CRM114-Status: GOOD ( 34.58 ) 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 | 240 ++++++++++++++++++++++++++++ 1 file changed, 240 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..bdff1c9 --- /dev/null +++ b/Documentation/admin-guide/qcom_minidump.rst @@ -0,0 +1,240 @@ +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. It provides appropriate +symbol to check its enablement and register client region. + +To simplify post mortem debugging, it 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 noted that minidump kernel driver depends on Qualcomm's +shared memory (SMEM) driver and its device tree entry (device +presence). If above support is present and Qualcomm boot firmware +has minidump support, so it is possible to dump linux region as +part of minidump collection. + +How a kernel client driver can register region with minidump +------------------------------------------------------------ + +Client driver can use qcom_minidump_ready() symbol to check if the +minidump driver is supported on the target and if it return -ENODEV +then it means minidump is not supported on this target and the client +should not try to register their minidump region further and +continue with their normal execution, and if it is supported it +can go ahead register its region with qcom_minidump_region_register(). + +Client need to fill their region by filling qcom_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 with +minidump. + + .. code-block:: c + + #include + [...] + + + [... inside a function ...] + struct qcom_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); + + [... Check if minidump is ready return -EPROBE_DEFER + if this is a probe function otherwise return accordingly ...] + err = qcom_minidump_ready(); + if (err && err != -ENODEV) + return -EPROBE_DEFER; + + 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; + + if (!err) { + ret = qcom_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) via 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 "both" +will set the mode to both (mini + full). + +sysfs 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_*.