Messages in this thread | | | Date | Thu, 25 May 2023 21:29:06 +0530 | Subject | Re: [PATCH v3 03/18] docs: qcom: Add qualcomm minidump guide | From | Mukesh Ojha <> |
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On 5/14/2023 12:16 AM, Randy Dunlap wrote: > > > On 5/3/23 10:02, Mukesh Ojha wrote: >> 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 <quic_mojha@quicinc.com> >> --- >> 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 > > RAM dumps for {post-mortem or postmortem} debugging. > > >> +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 > > contents > ? > >> + SS-ToC: Subsystem table of content > > contents > ? > >> + 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 > > memory (SMEM), > >> +allocates a small section of it to minidump table i.e also called > > table, i.e. > >> +global table of content (G-ToC). Each subsystem (APSS, ADSP, ...) has > > contents > >> +their own table of segments to be included in the minidump, all > > its own table > >> +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 > > its > >> +could be anywhere scattered in the DDR. >> + >> +Minidump kernel driver concept >> +------------------------------ >> + >> +Qualcomm minidump kernel driver adds the capability to add linux region > > Linux > >> +to be dumped as part of ram dump collection. At the moment, shared memory > > RAM > >> +driver creates plaform device for minidump driver and give a means to > > platform > >> +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 > > APSS > >> +address for the client whose addresses keeps on changing e.g Current stack > > changing, e.g., current stack > >> +address of task keep on changing on context switch for each core. So these > > keeps > >> +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 > > choose one: postmortem or post-mortem > >> +header as first region that gets updated each time a new region gets >> +registered. >> + >> +The solution supports extracting the ramdump/minidump produced either > > RAM dump/minidump > >> +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 > > s/thing // > >> +firmware whether it supports minidump or not. So, if the minidump >> +smem id is present in shared memory, it indicates that minidump > > SMEM ID > >> +is supported from boot firmware and it is possible to dump linux > > 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 > > needs > >> +structure object which consist of the region name, region's > > consists > >> +virtual and physical address and its size. >> + >> +Below is one sample client driver snippet which try to allocate > > tries > >> +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 <soc/qcom/qcom_minidump.h> >> + [...] >> + >> + >> + [... 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 > > DDR > >> +full dump) by writing appropriate value to Qualcomm's top control and >> +status register(tcsr) in driver/firmware/qcom_scm.c . > > register (tcsr) > >> + >> +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" > > DDR > >> +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 > > starting > >> +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 > > needs > >> +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 > > needs > >> +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 > > passed dexter.exe (Qualcomm tool) > >> +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 > > USB, i.e. regions > > >> +starts with md_*. >> + >> +Replacing the dexter.exe with some open source tool can be added as future >> +scope of this document. >
Thanks for the review, applied the change for the next version.
-- Mukesh
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