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@xxxxxxxxxxx> > --- > 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. -- ~Randy