Document explaining ISH HID operation and implementation. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> --- Documentation/hid/intel-ish-hid.txt | 375 ++++++++++++++++++++++++++++++++++++ 1 file changed, 375 insertions(+) create mode 100644 Documentation/hid/intel-ish-hid.txt diff --git a/Documentation/hid/intel-ish-hid.txt b/Documentation/hid/intel-ish-hid.txt new file mode 100644 index 0000000..83a636e --- /dev/null +++ b/Documentation/hid/intel-ish-hid.txt @@ -0,0 +1,375 @@ +Intel Integrated Sensor Hub (ISH) +=============================== + +A sensor hub enables the ability to offload sensor polling and algorithm +processing to a dedicated low power co-processor. This allows the core +processor to go into low power modes more often, resulting in the increased +battery life. +There are many vendors providing external sensor hubs confirming to HID +Sensor usage tables, and used in several tablets, 2 in 1 convertible laptops +and embedded products. Linux had this support since Linux 3.9. + +Intel® introduced integrated sensor hubs as a part of the SoC starting from +Cherry Trail and now supported on multiple generations of CPU packages. There +are many commercial devices already shipped with Integrated Sensor Hubs (ISH). +These ISH also comply to HID sensor specification, but the difference is the +transport protocol used for communication. The current external sensor hubs +mainly use HID over i2C or USB. But ISH doesn't use either i2c or USB. + +This document provides an overview of transport protocol and how it is +implemented. + + +ISH Implementation: Block Diagram +---------------------------------------- + --------------------------- + | User Space Applications | + --------------------------- + +----------------IIO ABI---------------- + -------------------------- + | IIO Sensor Drivers | + -------------------------- + -------------------------- + | IIO core | + -------------------------- + -------------------------- + | HID Sensor Hub MFD | + -------------------------- + -------------------------- + | HID Core | + -------------------------- + -------------------------- + | HID over ISH Client | + -------------------------- + -------------------------- + | ISH Client over ISHTP | + -------------------------- + -------------------------- + | ISH Transport (ISHTP) | + -------------------------- + -------------------------- + | IPC Drivers | + -------------------------- +OS +---------------- PCI ----------------- +Hardware + Firmware + ---------------------------- + | ISH Hardware/Firmware(FW) | + ---------------------------- + +------------------------------------------ + +High level processing in above blocks: + +--- +Hardware Interface +The ISH is exposed as "Non-VGA unclassified PCI device" to the host. The PCI +product and vendor IDs are changed from different generations of processors. So +the source code which enumerate drivers needs to update from generation to +generation. + +--- +Inter Processor Communication (IPC) driver: +Location: drivers/hid/intel-ish-hid/ipc + +The IPC message used memory mapped I/O. The registers are defined in +hw-ish-regs.h. + +IPC/FW message types +There are two types of messages, one for management of link and other messages +are to and from transport layers. + +TX and RX of Transport messages: +A set of memory mapped register offers support of multi byte messages TX and +RX (E.g.IPC_REG_ISH2HOST_MSG, IPC_REG_HOST2ISH_MSG). The messaging uses +doorbell register to trigger processing on client and server side. +The IPC layer maintains internal queues to sequence messages and send them in +order to the FW. Optionally the caller can register handler to get notification +of completion. + +Transport layer interface +To abstract HW level IPC communication a set of callbacks are registered. +The transport layer uses them to send and receive messages. +Refer to struct ishtp_hw_ops for callbacks. + +--- +ISH Transport layer +Location: drivers/hid/intel-ish-hid/ishtp/ + +A Generic Transport Layer +The transport layer is a bi-directional protocol, which defines: +- Set of commands to start, stop, connect, disconnect and flow control +(ishtp/hbm.h) for details +- A flow control mechanism to avoid buffer overflows + +This protocol resembles bus messages described in the following document: +http://www.intel.com/content/dam/www/public/us/en/documents/technical-\ +specifications/dcmi-hi-1-0-spec.pdf +Chater 7: Bus Message Layer + +DMA +The transport layer allocate 1 MB TX and 1 MB RX buffer. This buffer is divided +into slots of 4K buffer. This buffer is shared among all connected clients. +So when a message is to be sent or received by a client, it finds an empty +slot and either fill for TX or send DMA address to FW for RX. +By default all RX messages uses DMA as there is more upstream data for sensors +than downstream. For TX client send interface has flag to send via DMA, which +is not set by default as there is less TX data other setting some feature +reports by HID sensor hub driver. + +Ring Buffers +When a client initiate a connection, a ring or RX and TX buffers are allocated. +The size of ring can be specified by the client. HID client set 16 and 32 for +TX and RX buffers respectively. On send request from client, the data to be +sent is copied to one of the send ring buffer and scheduled to be sent using +bus message protocol. These buffers are required because the FW may have not +processed last message and may not have enough flow control credits to send. +Same thing holds true on receive side and flow control is required. + +Host Enumeration +The host enumeration bus command allow discovery of clients present in +the FW. There can be multiple sensor clients and clients for calibration +function. +To ease in implantation and allow independent driver handle each client +this transport layer takes advantage of Linux Bus driver model. Each +client is registered as device on the the transport bus (ishtp bus). + +ISH Client over generic transport layer +The ISH client defines interface to send and receive HID style command +and responses. Refer to ishtp-hid.h. +These commands are for" +- Get HID descriptor +- Get report descriptor +- Get/Set feature report +- Get input reports + +--- +HID over ISH Client +Location: drivers/hid/intel-ish-hid + +This implanted as ISHTP client driver, which +- enumerate HID devices under FW ISH client +- Get Report descriptor +- Register with HID core as a LL driver +- Process Get/Set feature request +- Get input reports + +---- +HID Sensor Hub MFD and IIO sensor drivers + +The functionality in these drivers is the same as an external sensor hub. +These drivers don't require changes to handle ISH other than some +optimizations. +---- + +======================================================================================== +End to End Startup HID transport Sequence Diagram + +HID-ISH-CLN ISHTP IPC HW + | | | | + | | |-----WAKE UP------------------>| + | | | | + | | |-----HOST READY--------------->| + | | | | + | | |<----MNG_RESET_NOTIFY_ACK----- | + | | | | + | |<----ISHTP_START------ | | + | | | | + | |<-----------------HOST_START_RES_CMD-------------------| + | | | | + | |------------------QUERY_SUBSCRIBER-------------------->| + | | | | + | |------------------HOST_ENUM_REQ_CMD------------------->| + | | | | + | |<-----------------HOST_ENUM_RES_CMD--------------------| + | | | | + | |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>| + | | | | + | |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------| + | Create new device on in ishtp bus | | + | | | | + | |------------------HOST_CLIENT_PROPERTIES_REQ_CMD------>| + | | | | + | |<-----------------HOST_CLIENT_PROPERTIES_RES_CMD-------| + | Create new device on in ishtp bus | | + | | | | + | |--Repeat HOST_CLIENT_PROPERTIES_REQ_CMD-till last one--| + | | | | + probed() + |----ishtp_cl_connect-->|----------------- CLIENT_CONNECT_REQ_CMD-------------->| + | | | | + | |<----------------CLIENT_CONNECT_RES_CMD----------------| + | | | | + |register event callback| | | + | | | | + |ishtp_cl_send( + HOSTIF_DM_ENUM_DEVICES) |----------fill ishtp_msg_hdr struct write to HW----- >| + | | | | + | | |<-----IRQ(IPC_PROTOCOL_ISHTP---| + | | | | + | |<------------ DMA_XFER---------------------------------| + |<--ENUM_DEVICE RSP-----| | | + | |------------ DMA_XFER_ACK----------------------------->| + | | | | +for each enumerated device + |ishtp_cl_send( + HOSTIF_GET_HID_DESCRIPTOR |----------fill ishtp_msg_hdr struct write to HW--- >| + | | | | + ...Response + | | | | +for each enumerated device + |ishtp_cl_send( + HOSTIF_GET_REPORT_DESCRIPTOR |----------fill ishtp_msg_hdr struct write to HW- >| + | | | | + | | | | + hid_allocate_device + | | | | + hid_add_device | | | + | | | | + + +======================================================================================== +ISH Debugging + +To debug ISH, event tracing mechanism is used. To enable debug logs +echo 1 > /sys/kernel/debug/tracing/events/intel_ish/enable +cat sys/kernel/debug/tracing/trace + +======================================================================================== +ISH IIO sysfs Example on Lenovo thinkpad Yoga 260 + +root@otcpl-ThinkPad-Yoga-260:~# tree -l /sys/bus/iio/devices/ +/sys/bus/iio/devices/ +├── iio:device0 -> ../../../devices/0044:8086:22D8.0001/HID-SENSOR-200073.9.auto/iio:device0 +│ ├── buffer +│ │ ├── enable +│ │ ├── length +│ │ └── watermark +... +│ ├── in_accel_hysteresis +│ ├── in_accel_offset +│ ├── in_accel_sampling_frequency +│ ├── in_accel_scale +│ ├── in_accel_x_raw +│ ├── in_accel_y_raw +│ ├── in_accel_z_raw +│ ├── name +│ ├── scan_elements +│ │ ├── in_accel_x_en +│ │ ├── in_accel_x_index +│ │ ├── in_accel_x_type +│ │ ├── in_accel_y_en +│ │ ├── in_accel_y_index +│ │ ├── in_accel_y_type +│ │ ├── in_accel_z_en +│ │ ├── in_accel_z_index +│ │ └── in_accel_z_type +... +│ │ ├── devices +│ │ │ │ ├── buffer +│ │ │ │ │ ├── enable +│ │ │ │ │ ├── length +│ │ │ │ │ └── watermark +│ │ │ │ ├── dev +│ │ │ │ ├── in_intensity_both_raw +│ │ │ │ ├── in_intensity_hysteresis +│ │ │ │ ├── in_intensity_offset +│ │ │ │ ├── in_intensity_sampling_frequency +│ │ │ │ ├── in_intensity_scale +│ │ │ │ ├── name +│ │ │ │ ├── scan_elements +│ │ │ │ │ ├── in_intensity_both_en +│ │ │ │ │ ├── in_intensity_both_index +│ │ │ │ │ └── in_intensity_both_type +│ │ │ │ ├── trigger +│ │ │ │ │ └── current_trigger +... +│ │ │ │ ├── buffer +│ │ │ │ │ ├── enable +│ │ │ │ │ ├── length +│ │ │ │ │ └── watermark +│ │ │ │ ├── dev +│ │ │ │ ├── in_magn_hysteresis +│ │ │ │ ├── in_magn_offset +│ │ │ │ ├── in_magn_sampling_frequency +│ │ │ │ ├── in_magn_scale +│ │ │ │ ├── in_magn_x_raw +│ │ │ │ ├── in_magn_y_raw +│ │ │ │ ├── in_magn_z_raw +│ │ │ │ ├── in_rot_from_north_magnetic_tilt_comp_raw +│ │ │ │ ├── in_rot_hysteresis +│ │ │ │ ├── in_rot_offset +│ │ │ │ ├── in_rot_sampling_frequency +│ │ │ │ ├── in_rot_scale +│ │ │ │ ├── name +... +│ │ │ │ ├── scan_elements +│ │ │ │ │ ├── in_magn_x_en +│ │ │ │ │ ├── in_magn_x_index +│ │ │ │ │ ├── in_magn_x_type +│ │ │ │ │ ├── in_magn_y_en +│ │ │ │ │ ├── in_magn_y_index +│ │ │ │ │ ├── in_magn_y_type +│ │ │ │ │ ├── in_magn_z_en +│ │ │ │ │ ├── in_magn_z_index +│ │ │ │ │ ├── in_magn_z_type +│ │ │ │ │ ├── in_rot_from_north_magnetic_tilt_comp_en +│ │ │ │ │ ├── in_rot_from_north_magnetic_tilt_comp_index +│ │ │ │ │ └── in_rot_from_north_magnetic_tilt_comp_type +│ │ │ │ ├── trigger +│ │ │ │ │ └── current_trigger +... +│ │ │ │ ├── buffer +│ │ │ │ │ ├── enable +│ │ │ │ │ ├── length +│ │ │ │ │ └── watermark +│ │ │ │ ├── dev +│ │ │ │ ├── in_anglvel_hysteresis +│ │ │ │ ├── in_anglvel_offset +│ │ │ │ ├── in_anglvel_sampling_frequency +│ │ │ │ ├── in_anglvel_scale +│ │ │ │ ├── in_anglvel_x_raw +│ │ │ │ ├── in_anglvel_y_raw +│ │ │ │ ├── in_anglvel_z_raw +│ │ │ │ ├── name +│ │ │ │ ├── scan_elements +│ │ │ │ │ ├── in_anglvel_x_en +│ │ │ │ │ ├── in_anglvel_x_index +│ │ │ │ │ ├── in_anglvel_x_type +│ │ │ │ │ ├── in_anglvel_y_en +│ │ │ │ │ ├── in_anglvel_y_index +│ │ │ │ │ ├── in_anglvel_y_type +│ │ │ │ │ ├── in_anglvel_z_en +│ │ │ │ │ ├── in_anglvel_z_index +│ │ │ │ │ └── in_anglvel_z_type +│ │ │ │ ├── trigger +│ │ │ │ │ └── current_trigger +... +│ │ │ │ ├── buffer +│ │ │ │ │ ├── enable +│ │ │ │ │ ├── length +│ │ │ │ │ └── watermark +│ │ │ │ ├── dev +│ │ │ │ ├── in_anglvel_hysteresis +│ │ │ │ ├── in_anglvel_offset +│ │ │ │ ├── in_anglvel_sampling_frequency +│ │ │ │ ├── in_anglvel_scale +│ │ │ │ ├── in_anglvel_x_raw +│ │ │ │ ├── in_anglvel_y_raw +│ │ │ │ ├── in_anglvel_z_raw +│ │ │ │ ├── name +│ │ │ │ ├── scan_elements +│ │ │ │ │ ├── in_anglvel_x_en +│ │ │ │ │ ├── in_anglvel_x_index +│ │ │ │ │ ├── in_anglvel_x_type +│ │ │ │ │ ├── in_anglvel_y_en +│ │ │ │ │ ├── in_anglvel_y_index +│ │ │ │ │ ├── in_anglvel_y_type +│ │ │ │ │ ├── in_anglvel_z_en +│ │ │ │ │ ├── in_anglvel_z_index +│ │ │ │ │ └── in_anglvel_z_type +│ │ │ │ ├── trigger +│ │ │ │ │ └── current_trigger +... + -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
