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Diffstat (limited to 'Documentation/scsi/libsas.txt')
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diff --git a/Documentation/scsi/libsas.txt b/Documentation/scsi/libsas.txt new file mode 100644 index 000000000000..9e2078b2a615 --- /dev/null +++ b/Documentation/scsi/libsas.txt @@ -0,0 +1,484 @@ +SAS Layer +--------- + +The SAS Layer is a management infrastructure which manages +SAS LLDDs. It sits between SCSI Core and SAS LLDDs. The +layout is as follows: while SCSI Core is concerned with +SAM/SPC issues, and a SAS LLDD+sequencer is concerned with +phy/OOB/link management, the SAS layer is concerned with: + + * SAS Phy/Port/HA event management (LLDD generates, + SAS Layer processes), + * SAS Port management (creation/destruction), + * SAS Domain discovery and revalidation, + * SAS Domain device management, + * SCSI Host registration/unregistration, + * Device registration with SCSI Core (SAS) or libata + (SATA), and + * Expander management and exporting expander control + to user space. + +A SAS LLDD is a PCI device driver. It is concerned with +phy/OOB management, and vendor specific tasks and generates +events to the SAS layer. + +The SAS Layer does most SAS tasks as outlined in the SAS 1.1 +spec. + +The sas_ha_struct describes the SAS LLDD to the SAS layer. +Most of it is used by the SAS Layer but a few fields need to +be initialized by the LLDDs. + +After initializing your hardware, from the probe() function +you call sas_register_ha(). It will register your LLDD with +the SCSI subsystem, creating a SCSI host and it will +register your SAS driver with the sysfs SAS tree it creates. +It will then return. Then you enable your phys to actually +start OOB (at which point your driver will start calling the +notify_* event callbacks). + +Structure descriptions: + +struct sas_phy -------------------- +Normally this is statically embedded to your driver's +phy structure: + struct my_phy { + blah; + struct sas_phy sas_phy; + bleh; + }; +And then all the phys are an array of my_phy in your HA +struct (shown below). + +Then as you go along and initialize your phys you also +initialize the sas_phy struct, along with your own +phy structure. + +In general, the phys are managed by the LLDD and the ports +are managed by the SAS layer. So the phys are initialized +and updated by the LLDD and the ports are initialized and +updated by the SAS layer. + +There is a scheme where the LLDD can RW certain fields, +and the SAS layer can only read such ones, and vice versa. +The idea is to avoid unnecessary locking. + +enabled -- must be set (0/1) +id -- must be set [0,MAX_PHYS) +class, proto, type, role, oob_mode, linkrate -- must be set +oob_mode -- you set this when OOB has finished and then notify +the SAS Layer. + +sas_addr -- this normally points to an array holding the sas +address of the phy, possibly somewhere in your my_phy +struct. + +attached_sas_addr -- set this when you (LLDD) receive an +IDENTIFY frame or a FIS frame, _before_ notifying the SAS +layer. The idea is that sometimes the LLDD may want to fake +or provide a different SAS address on that phy/port and this +allows it to do this. At best you should copy the sas +address from the IDENTIFY frame or maybe generate a SAS +address for SATA directly attached devices. The Discover +process may later change this. + +frame_rcvd -- this is where you copy the IDENTIFY/FIS frame +when you get it; you lock, copy, set frame_rcvd_size and +unlock the lock, and then call the event. It is a pointer +since there's no way to know your hw frame size _exactly_, +so you define the actual array in your phy struct and let +this pointer point to it. You copy the frame from your +DMAable memory to that area holding the lock. + +sas_prim -- this is where primitives go when they're +received. See sas.h. Grab the lock, set the primitive, +release the lock, notify. + +port -- this points to the sas_port if the phy belongs +to a port -- the LLDD only reads this. It points to the +sas_port this phy is part of. Set by the SAS Layer. + +ha -- may be set; the SAS layer sets it anyway. + +lldd_phy -- you should set this to point to your phy so you +can find your way around faster when the SAS layer calls one +of your callbacks and passes you a phy. If the sas_phy is +embedded you can also use container_of -- whatever you +prefer. + + +struct sas_port -------------------- +The LLDD doesn't set any fields of this struct -- it only +reads them. They should be self explanatory. + +phy_mask is 32 bit, this should be enough for now, as I +haven't heard of a HA having more than 8 phys. + +lldd_port -- I haven't found use for that -- maybe other +LLDD who wish to have internal port representation can make +use of this. + + +struct sas_ha_struct -------------------- +It normally is statically declared in your own LLDD +structure describing your adapter: +struct my_sas_ha { + blah; + struct sas_ha_struct sas_ha; + struct my_phy phys[MAX_PHYS]; + struct sas_port sas_ports[MAX_PHYS]; /* (1) */ + bleh; +}; + +(1) If your LLDD doesn't have its own port representation. + +What needs to be initialized (sample function given below). + +pcidev +sas_addr -- since the SAS layer doesn't want to mess with + memory allocation, etc, this points to statically + allocated array somewhere (say in your host adapter + structure) and holds the SAS address of the host + adapter as given by you or the manufacturer, etc. +sas_port +sas_phy -- an array of pointers to structures. (see + note above on sas_addr). + These must be set. See more notes below. +num_phys -- the number of phys present in the sas_phy array, + and the number of ports present in the sas_port + array. There can be a maximum num_phys ports (one per + port) so we drop the num_ports, and only use + num_phys. + +The event interface: + + /* LLDD calls these to notify the class of an event. */ + void (*notify_ha_event)(struct sas_ha_struct *, enum ha_event); + void (*notify_port_event)(struct sas_phy *, enum port_event); + void (*notify_phy_event)(struct sas_phy *, enum phy_event); + +When sas_register_ha() returns, those are set and can be +called by the LLDD to notify the SAS layer of such events +the SAS layer. + +The port notification: + + /* The class calls these to notify the LLDD of an event. */ + void (*lldd_port_formed)(struct sas_phy *); + void (*lldd_port_deformed)(struct sas_phy *); + +If the LLDD wants notification when a port has been formed +or deformed it sets those to a function satisfying the type. + +A SAS LLDD should also implement at least one of the Task +Management Functions (TMFs) described in SAM: + + /* Task Management Functions. Must be called from process context. */ + int (*lldd_abort_task)(struct sas_task *); + int (*lldd_abort_task_set)(struct domain_device *, u8 *lun); + int (*lldd_clear_aca)(struct domain_device *, u8 *lun); + int (*lldd_clear_task_set)(struct domain_device *, u8 *lun); + int (*lldd_I_T_nexus_reset)(struct domain_device *); + int (*lldd_lu_reset)(struct domain_device *, u8 *lun); + int (*lldd_query_task)(struct sas_task *); + +For more information please read SAM from T10.org. + +Port and Adapter management: + + /* Port and Adapter management */ + int (*lldd_clear_nexus_port)(struct sas_port *); + int (*lldd_clear_nexus_ha)(struct sas_ha_struct *); + +A SAS LLDD should implement at least one of those. + +Phy management: + + /* Phy management */ + int (*lldd_control_phy)(struct sas_phy *, enum phy_func); + +lldd_ha -- set this to point to your HA struct. You can also +use container_of if you embedded it as shown above. + +A sample initialization and registration function +can look like this (called last thing from probe()) +*but* before you enable the phys to do OOB: + +static int register_sas_ha(struct my_sas_ha *my_ha) +{ + int i; + static struct sas_phy *sas_phys[MAX_PHYS]; + static struct sas_port *sas_ports[MAX_PHYS]; + + my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0]; + + for (i = 0; i < MAX_PHYS; i++) { + sas_phys[i] = &my_ha->phys[i].sas_phy; + sas_ports[i] = &my_ha->sas_ports[i]; + } + + my_ha->sas_ha.sas_phy = sas_phys; + my_ha->sas_ha.sas_port = sas_ports; + my_ha->sas_ha.num_phys = MAX_PHYS; + + my_ha->sas_ha.lldd_port_formed = my_port_formed; + + my_ha->sas_ha.lldd_dev_found = my_dev_found; + my_ha->sas_ha.lldd_dev_gone = my_dev_gone; + + my_ha->sas_ha.lldd_max_execute_num = lldd_max_execute_num; (1) + + my_ha->sas_ha.lldd_queue_size = ha_can_queue; + my_ha->sas_ha.lldd_execute_task = my_execute_task; + + my_ha->sas_ha.lldd_abort_task = my_abort_task; + my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set; + my_ha->sas_ha.lldd_clear_aca = my_clear_aca; + my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set; + my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2) + my_ha->sas_ha.lldd_lu_reset = my_lu_reset; + my_ha->sas_ha.lldd_query_task = my_query_task; + + my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port; + my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha; + + my_ha->sas_ha.lldd_control_phy = my_control_phy; + + return sas_register_ha(&my_ha->sas_ha); +} + +(1) This is normally a LLDD parameter, something of the +lines of a task collector. What it tells the SAS Layer is +whether the SAS layer should run in Direct Mode (default: +value 0 or 1) or Task Collector Mode (value greater than 1). + +In Direct Mode, the SAS Layer calls Execute Task as soon as +it has a command to send to the SDS, _and_ this is a single +command, i.e. not linked. + +Some hardware (e.g. aic94xx) has the capability to DMA more +than one task at a time (interrupt) from host memory. Task +Collector Mode is an optional feature for HAs which support +this in their hardware. (Again, it is completely optional +even if your hardware supports it.) + +In Task Collector Mode, the SAS Layer would do _natural_ +coalescing of tasks and at the appropriate moment it would +call your driver to DMA more than one task in a single HA +interrupt. DMBS may want to use this by insmod/modprobe +setting the lldd_max_execute_num to something greater than +1. + +(2) SAS 1.1 does not define I_T Nexus Reset TMF. + +Events +------ + +Events are _the only way_ a SAS LLDD notifies the SAS layer +of anything. There is no other method or way a LLDD to tell +the SAS layer of anything happening internally or in the SAS +domain. + +Phy events: + PHYE_LOSS_OF_SIGNAL, (C) + PHYE_OOB_DONE, + PHYE_OOB_ERROR, (C) + PHYE_SPINUP_HOLD. + +Port events, passed on a _phy_: + PORTE_BYTES_DMAED, (M) + PORTE_BROADCAST_RCVD, (E) + PORTE_LINK_RESET_ERR, (C) + PORTE_TIMER_EVENT, (C) + PORTE_HARD_RESET. + +Host Adapter event: + HAE_RESET + +A SAS LLDD should be able to generate + - at least one event from group C (choice), + - events marked M (mandatory) are mandatory (only one), + - events marked E (expander) if it wants the SAS layer + to handle domain revalidation (only one such). + - Unmarked events are optional. + +Meaning: + +HAE_RESET -- when your HA got internal error and was reset. + +PORTE_BYTES_DMAED -- on receiving an IDENTIFY/FIS frame +PORTE_BROADCAST_RCVD -- on receiving a primitive +PORTE_LINK_RESET_ERR -- timer expired, loss of signal, loss +of DWS, etc. (*) +PORTE_TIMER_EVENT -- DWS reset timeout timer expired (*) +PORTE_HARD_RESET -- Hard Reset primitive received. + +PHYE_LOSS_OF_SIGNAL -- the device is gone (*) +PHYE_OOB_DONE -- OOB went fine and oob_mode is valid +PHYE_OOB_ERROR -- Error while doing OOB, the device probably +got disconnected. (*) +PHYE_SPINUP_HOLD -- SATA is present, COMWAKE not sent. + +(*) should set/clear the appropriate fields in the phy, + or alternatively call the inlined sas_phy_disconnected() + which is just a helper, from their tasklet. + +The Execute Command SCSI RPC: + + int (*lldd_execute_task)(struct sas_task *, int num, + unsigned long gfp_flags); + +Used to queue a task to the SAS LLDD. @task is the tasks to +be executed. @num should be the number of tasks being +queued at this function call (they are linked listed via +task::list), @gfp_mask should be the gfp_mask defining the +context of the caller. + +This function should implement the Execute Command SCSI RPC, +or if you're sending a SCSI Task as linked commands, you +should also use this function. + +That is, when lldd_execute_task() is called, the command(s) +go out on the transport *immediately*. There is *no* +queuing of any sort and at any level in a SAS LLDD. + +The use of task::list is two-fold, one for linked commands, +the other discussed below. + +It is possible to queue up more than one task at a time, by +initializing the list element of struct sas_task, and +passing the number of tasks enlisted in this manner in num. + +Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued; + 0, the task(s) were queued. + +If you want to pass num > 1, then either +A) you're the only caller of this function and keep track + of what you've queued to the LLDD, or +B) you know what you're doing and have a strategy of + retrying. + +As opposed to queuing one task at a time (function call), +batch queuing of tasks, by having num > 1, greatly +simplifies LLDD code, sequencer code, and _hardware design_, +and has some performance advantages in certain situations +(DBMS). + +The LLDD advertises if it can take more than one command at +a time at lldd_execute_task(), by setting the +lldd_max_execute_num parameter (controlled by "collector" +module parameter in aic94xx SAS LLDD). + +You should leave this to the default 1, unless you know what +you're doing. + +This is a function of the LLDD, to which the SAS layer can +cater to. + +int lldd_queue_size + The host adapter's queue size. This is the maximum +number of commands the lldd can have pending to domain +devices on behalf of all upper layers submitting through +lldd_execute_task(). + +You really want to set this to something (much) larger than +1. + +This _really_ has absolutely nothing to do with queuing. +There is no queuing in SAS LLDDs. + +struct sas_task { + dev -- the device this task is destined to + list -- must be initialized (INIT_LIST_HEAD) + task_proto -- _one_ of enum sas_proto + scatter -- pointer to scatter gather list array + num_scatter -- number of elements in scatter + total_xfer_len -- total number of bytes expected to be transfered + data_dir -- PCI_DMA_... + task_done -- callback when the task has finished execution +}; + +When an external entity, entity other than the LLDD or the +SAS Layer, wants to work with a struct domain_device, it +_must_ call kobject_get() when getting a handle on the +device and kobject_put() when it is done with the device. + +This does two things: + A) implements proper kfree() for the device; + B) increments/decrements the kref for all players: + domain_device + all domain_device's ... (if past an expander) + port + host adapter + pci device + and up the ladder, etc. + +DISCOVERY +--------- + +The sysfs tree has the following purposes: + a) It shows you the physical layout of the SAS domain at + the current time, i.e. how the domain looks in the + physical world right now. + b) Shows some device parameters _at_discovery_time_. + +This is a link to the tree(1) program, very useful in +viewing the SAS domain: +ftp://mama.indstate.edu/linux/tree/ +I expect user space applications to actually create a +graphical interface of this. + +That is, the sysfs domain tree doesn't show or keep state if +you e.g., change the meaning of the READY LED MEANING +setting, but it does show you the current connection status +of the domain device. + +Keeping internal device state changes is responsibility of +upper layers (Command set drivers) and user space. + +When a device or devices are unplugged from the domain, this +is reflected in the sysfs tree immediately, and the device(s) +removed from the system. + +The structure domain_device describes any device in the SAS +domain. It is completely managed by the SAS layer. A task +points to a domain device, this is how the SAS LLDD knows +where to send the task(s) to. A SAS LLDD only reads the +contents of the domain_device structure, but it never creates +or destroys one. + +Expander management from User Space +----------------------------------- + +In each expander directory in sysfs, there is a file called +"smp_portal". It is a binary sysfs attribute file, which +implements an SMP portal (Note: this is *NOT* an SMP port), +to which user space applications can send SMP requests and +receive SMP responses. + +Functionality is deceptively simple: + +1. Build the SMP frame you want to send. The format and layout + is described in the SAS spec. Leave the CRC field equal 0. +open(2) +2. Open the expander's SMP portal sysfs file in RW mode. +write(2) +3. Write the frame you built in 1. +read(2) +4. Read the amount of data you expect to receive for the frame you built. + If you receive different amount of data you expected to receive, + then there was some kind of error. +close(2) +All this process is shown in detail in the function do_smp_func() +and its callers, in the file "expander_conf.c". + +The kernel functionality is implemented in the file +"sas_expander.c". + +The program "expander_conf.c" implements this. It takes one +argument, the sysfs file name of the SMP portal to the +expander, and gives expander information, including routing +tables. + +The SMP portal gives you complete control of the expander, +so please be careful. |
