On Wed, Jun 28, 2023 at 6:36 AM Mukesh Ojha <quic_mojha@xxxxxxxxxxx> 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/index.rst | 1 + > Documentation/admin-guide/qcom_minidump.rst | 293 ++++++++++++++++++++++++++++ > 2 files changed, 294 insertions(+) > create mode 100644 Documentation/admin-guide/qcom_minidump.rst > > diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst > index 43ea35613dfc..251d070486c2 100644 > --- a/Documentation/admin-guide/index.rst > +++ b/Documentation/admin-guide/index.rst > @@ -120,6 +120,7 @@ configure specific aspects of kernel behavior to your liking. > perf-security > pm/index > pnp > + qcom_minidump > rapidio > ras > rtc > diff --git a/Documentation/admin-guide/qcom_minidump.rst b/Documentation/admin-guide/qcom_minidump.rst > new file mode 100644 > index 000000000000..a3a8cfee4555 > --- /dev/null > +++ b/Documentation/admin-guide/qcom_minidump.rst > @@ -0,0 +1,293 @@ > +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 RAM dumps 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 contents > + SS-ToC: Subsystem table of contents > + SS0-SSn: Subsystem numbered from 0 to n > + > +It depends on targets how the underlying hardware taking care of the > +implementation part for minidump like above diagram is for shared > +memory and it is possible that this could be implemented via memory > +mapped regions but the general idea remain same. > + > +In this document, SMEM will be used as the backend implementation of > +minidump. > + > +SMEM as backend > +---------------- > + > +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 contents (G-ToC). Each subsystem (APSS, ADSP, ...) has > +its 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 its size etc. and it > +could be anywhere scattered in the DDR. > + > +Minidump kernel driver concept > +------------------------------ > +:: > + > + Minidump Client-1 Client-2 Client-5 Client-n > + | | | | > + | | ... | ... | > + | | | | > + | | | | > + | | | | > + | | | | > + | | | | > + | | | | > + | +---+--------------+----+ | > + +-----------+ qcom_minidump(core) +--------+ > + | | > + +------+-----+------+---+ > + | | | > + | | | > + +---------------+ | +--------------------+ > + | | | > + | | | > + | | | > + v v v > + +-------------------+ +-------------------+ +------------------+ > + |qcom_minidump_smem | |qcom_minidump_mmio | | qcom_minidump_rm | > + | | | | | | > + +-------------------+ +-------------------+ +------------------+ > + Shared memory Memory mapped IO Resource manager > + (backend) (backend) (backend) > + > + > +Kernel implementation of minidump driver is divided into two parts one is, > +the core implementation called frontend driver ``qcom_minidump.c`` and this > +is the driver will be exposing the API for clients and the other part is, > +backend driver and its depends whether it is based on SMEM, MMIO or some > +other way corressponding driver will be hooking itself up with the core > +driver to get itself working. As of now, at a time one and only one backend > +can be attached to the front-end either it is HOST or a guest VM. > + > +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 platform device for minidump driver and give a means to > +APSS minidump to initialize itself on probe. > + > +This driver provides ``qcom_minidump_region_register`` and > +``qcom_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 keeps on changing on context switch for each core. So these > +clients can update their addresses with ``qcom_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 RAM dump/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 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_minidump_region_register`` API's to > +register and ``qcom_minidump_region_unregister`` to unregister > +their region from minidump driver. > + > +Client needs to fill their region by filling ``qcom_minidump_region`` > +structure object which consists of the region name, region's > +virtual and physical address and its size. > + > +Below is one sample client driver snippet which tries 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 <soc/qcom/qcom_minidump.h> > + [...] > + > + > + [... 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); > + > + [... 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_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 RAM 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 RAM 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 starting with name ``md_*`` in PCAT configured directory > +in x86_64 machine, so for above example from the client it will be So I can't use my QCom laptop or M1 MacBook? This text won't age well, so perhaps reword it. Rob