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soc: qcom: rpmh-rsc: A lot of comments 

I've been pouring through the rpmh-rsc code and trying to understand
it.  Document everything to the best of my ability.  All documentation
here is strictly from code analysis--no actual knowledge of the
hardware was used.  If something is wrong in here I either
misunderstood the code, had a typo, or the code has a bug in it
leading to my incorrect understanding.

In a few places here I have documented things that don't make tons of
sense.  A future patch will try to address this.  While this means I'm
adding comments / todos and then later fixing them in the series, it
seemed more urgent to get things documented first so that people could
understand the later patches.

Any comments I adjusted I also tried to make match kernel-doc better.
Specifically:
- kernel-doc says do not leave a blank line between the function
  description and the arguments
- kernel-doc examples always have things starting w/ a capital and
  ending with a period.

This should be a no-op.  It's just comment changes.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Maulik Shah <mkshah@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20200413100321.v4.6.I52653eb85d7dc8981ee0dafcd0b6cc0f273e9425@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
This commit is contained in:
Douglas Anderson 2020-04-13 10:04:11 -07:00 committed by Bjorn Andersson
parent 1bc92a933f
commit e40b0c1628
2 changed files with 247 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
drivers/soc/qcom/rpmh-internal.h
View File

@ -22,15 +22,24 @@ struct rsc_drv;
* struct tcs_group: group of Trigger Command Sets (TCS) to send state requests
* to the controller
*
* @drv: the controller
* @type: type of the TCS in this group - active, sleep, wake
* @mask: mask of the TCSes relative to all the TCSes in the RSC
* @offset: start of the TCS group relative to the TCSes in the RSC
* @num_tcs: number of TCSes in this type
* @ncpt: number of commands in each TCS
* @lock: lock for synchronizing this TCS writes
* @req: requests that are sent from the TCS
* @slots: indicates which of @cmd_addr are occupied
* @drv: The controller.
* @type: Type of the TCS in this group - active, sleep, wake.
* @mask: Mask of the TCSes relative to all the TCSes in the RSC.
* @offset: Start of the TCS group relative to the TCSes in the RSC.
* @num_tcs: Number of TCSes in this type.
* @ncpt: Number of commands in each TCS.
* @lock: Lock for synchronizing this TCS writes.
* @req: Requests that are sent from the TCS; only used for ACTIVE_ONLY
* transfers (could be on a wake/sleep TCS if we are borrowing for
* an ACTIVE_ONLY transfer).
* Start: grab drv->lock, set req, set tcs_in_use, drop drv->lock,
* trigger
* End: get irq, access req,
* grab drv->lock, clear tcs_in_use, drop drv->lock
* @slots: Indicates which of @cmd_addr are occupied; only used for
* SLEEP / WAKE TCSs. Things are tightly packed in the
* case that (ncpt < MAX_CMDS_PER_TCS). That is if ncpt = 2 and
* MAX_CMDS_PER_TCS = 16 then bit[2] = the first bit in 2nd TCS.
*/
struct tcs_group {
struct rsc_drv *drv;
@ -82,19 +91,28 @@ struct rpmh_ctrlr {
* struct rsc_drv: the Direct Resource Voter (DRV) of the
* Resource State Coordinator controller (RSC)
*
* @name: Controller identifier
* @tcs_base: Start address of the TCS registers in this controller
* @id: Instance id in the controller (Direct Resource Voter)
* @num_tcs: Number of TCSes in this DRV
* @rsc_pm: CPU PM notifier for controller
* Used when solver mode is not present
* @cpus_entered_pm: CPU mask for cpus in idle power collapse
* Used when solver mode is not present
* @tcs: TCS groups
* @tcs_in_use: S/W state of the TCS
* @lock: Synchronize state of the controller
* @pm_lock: Synchronize during PM notifications
* Used when solver mode is not present
* @name: Controller identifier.
* @tcs_base: Start address of the TCS registers in this controller.
* @id: Instance id in the controller (Direct Resource Voter).
* @num_tcs: Number of TCSes in this DRV.
* @rsc_pm: CPU PM notifier for controller.
* Used when solver mode is not present.
* @cpus_entered_pm: CPU mask for cpus in idle power collapse.
* Used when solver mode is not present.
* @tcs: TCS groups.
* @tcs_in_use: S/W state of the TCS; only set for ACTIVE_ONLY
* transfers, but might show a sleep/wake TCS in use if
* it was borrowed for an active_only transfer. You
* must hold both the lock in this struct and the
* tcs_lock for the TCS in order to mark a TCS as
* in-use, but you only need the lock in this structure
* (aka the drv->lock) to mark one freed.
* @lock: Synchronize state of the controller. If you will be
* grabbing this lock and a tcs_lock at the same time,
* grab the tcs_lock first so we always have a
* consistent lock ordering.
* @pm_lock: Synchronize during PM notifications.
* Used when solver mode is not present.
* @client: Handle to the DRV's client.
*/
struct rsc_drv {

222
drivers/soc/qcom/rpmh-rsc.c
View File

@ -171,12 +171,39 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
}
}
/**
* tcs_is_free() - Return if a TCS is totally free.
* @drv: The RSC controller.
* @tcs_id: The global ID of this TCS.
*
* Returns true if nobody has claimed this TCS (by setting tcs_in_use).
* If the TCS looks free, checks that the hardware agrees.
*
* Context: Must be called with the drv->lock held or the tcs_lock for the TCS
* being tested. If only the tcs_lock is held then it is possible that
* this function will return that a tcs is still busy when it has been
* recently been freed but it will never return free when a TCS is
* actually in use.
*
* Return: true if the given TCS is free.
*/
static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
{
return !test_bit(tcs_id, drv->tcs_in_use) &&
read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id);
}
/**
* tcs_invalidate() - Invalidate all TCSes of the given type (sleep or wake).
* @drv: The RSC controller.
* @type: SLEEP_TCS or WAKE_TCS
*
* This will clear the "slots" variable of the given tcs_group and also
* tell the hardware to forget about all entries.
*
* Return: 0 if no problem, or -EAGAIN if the caller should try again in a
* bit. Caller should make sure to enable interrupts between tries.
*/
static int tcs_invalidate(struct rsc_drv *drv, int type)
{
int m;
@ -203,9 +230,11 @@ static int tcs_invalidate(struct rsc_drv *drv, int type)
}
/**
* rpmh_rsc_invalidate - Invalidate sleep and wake TCSes
* rpmh_rsc_invalidate() - Invalidate sleep and wake TCSes.
* @drv: The RSC controller.
*
* @drv: the RSC controller
* Return: 0 if no problem, or -EAGAIN if the caller should try again in a
* bit. Caller should make sure to enable interrupts between tries.
*/
int rpmh_rsc_invalidate(struct rsc_drv *drv)
{
@ -218,6 +247,18 @@ int rpmh_rsc_invalidate(struct rsc_drv *drv)
return ret;
}
/**
* get_tcs_for_msg() - Get the tcs_group used to send the given message.
* @drv: The RSC controller.
* @msg: The message we want to send.
*
* This is normally pretty straightforward except if we are trying to send
* an ACTIVE_ONLY message but don't have any active_only TCSes.
*
* Called without drv->lock held and with no tcs_lock locks held.
*
* Return: A pointer to a tcs_group or an ERR_PTR.
*/
static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv,
const struct tcs_request *msg)
{
@ -241,7 +282,9 @@ static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv,
/*
* If we are making an active request on a RSC that does not have a
* dedicated TCS for active state use, then re-purpose a wake TCS to
* send active votes.
* send active votes. This is safe because we ensure any active-only
* transfers have finished before we use it (maybe by running from
* the last CPU in PM code).
*/
tcs = &drv->tcs[type];
if (msg->state == RPMH_ACTIVE_ONLY_STATE && !tcs->num_tcs)
@ -250,6 +293,22 @@ static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv,
return tcs;
}
/**
* get_req_from_tcs() - Get a stashed request that was xfering on the given TCS.
* @drv: The RSC controller.
* @tcs_id: The global ID of this TCS.
*
* For ACTIVE_ONLY transfers we want to call back into the client when the
* transfer finishes. To do this we need the "request" that the client
* originally provided us. This function grabs the request that we stashed
* when we started the transfer.
*
* This only makes sense for ACTIVE_ONLY transfers since those are the only
* ones we track sending (the only ones we enable interrupts for and the only
* ones we call back to the client for).
*
* Return: The stashed request.
*/
static const struct tcs_request *get_req_from_tcs(struct rsc_drv *drv,
int tcs_id)
{
@ -265,6 +324,23 @@ static const struct tcs_request *get_req_from_tcs(struct rsc_drv *drv,
return NULL;
}
/**
* __tcs_set_trigger() - Start xfer on a TCS or unset trigger on a borrowed TCS
* @drv: The controller.
* @tcs_id: The global ID of this TCS.
* @trigger: If true then untrigger/retrigger. If false then just untrigger.
*
* In the normal case we only ever call with "trigger=true" to start a
* transfer. That will un-trigger/disable the TCS from the last transfer
* then trigger/enable for this transfer.
*
* If we borrowed a wake TCS for an active-only transfer we'll also call
* this function with "trigger=false" to just do the un-trigger/disable
* before using the TCS for wake purposes again.
*
* Note that the AP is only in charge of triggering active-only transfers.
* The AP never triggers sleep/wake values using this function.
*/
static void __tcs_set_trigger(struct rsc_drv *drv, int tcs_id, bool trigger)
{
u32 enable;
@ -289,6 +365,15 @@ static void __tcs_set_trigger(struct rsc_drv *drv, int tcs_id, bool trigger)
}
}
/**
* enable_tcs_irq() - Enable or disable interrupts on the given TCS.
* @drv: The controller.
* @tcs_id: The global ID of this TCS.
* @enable: If true then enable; if false then disable
*
* We only ever call this when we borrow a wake TCS for an active-only
* transfer. For active-only TCSes interrupts are always left enabled.
*/
static void enable_tcs_irq(struct rsc_drv *drv, int tcs_id, bool enable)
{
u32 data;
@ -302,7 +387,14 @@ static void enable_tcs_irq(struct rsc_drv *drv, int tcs_id, bool enable)
}
/**
* tcs_tx_done: TX Done interrupt handler
* tcs_tx_done() - TX Done interrupt handler.
* @irq: The IRQ number (ignored).
* @p: Pointer to "struct rsc_drv".
*
* Called for ACTIVE_ONLY transfers (those are the only ones we enable the
* IRQ for) when a transfer is done.
*
* Return: IRQ_HANDLED
*/
static irqreturn_t tcs_tx_done(int irq, void *p)
{
@ -367,6 +459,16 @@ static irqreturn_t tcs_tx_done(int irq, void *p)
return IRQ_HANDLED;
}
/**
* __tcs_buffer_write() - Write to TCS hardware from a request; don't trigger.
* @drv: The controller.
* @tcs_id: The global ID of this TCS.
* @cmd_id: The index within the TCS to start writing.
* @msg: The message we want to send, which will contain several addr/data
* pairs to program (but few enough that they all fit in one TCS).
*
* This is used for all types of transfers (active, sleep, and wake).
*/
static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
const struct tcs_request *msg)
{
@ -400,6 +502,26 @@ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
write_tcs_reg(drv, RSC_DRV_CMD_ENABLE, tcs_id, cmd_enable);
}
/**
* check_for_req_inflight() - Look to see if conflicting cmds are in flight.
* @drv: The controller.
* @tcs: A pointer to the tcs_group used for ACTIVE_ONLY transfers.
* @msg: The message we want to send, which will contain several addr/data
* pairs to program (but few enough that they all fit in one TCS).
*
* This will walk through the TCSes in the group and check if any of them
* appear to be sending to addresses referenced in the message. If it finds
* one it'll return -EBUSY.
*
* Only for use for active-only transfers.
*
* Must be called with the drv->lock held since that protects tcs_in_use.
*
* Return: 0 if nothing in flight or -EBUSY if we should try again later.
* The caller must re-enable interrupts between tries since that's
* the only way tcs_is_free() will ever return true and the only way
* RSC_DRV_CMD_ENABLE will ever be cleared.
*/
static int check_for_req_inflight(struct rsc_drv *drv, struct tcs_group *tcs,
const struct tcs_request *msg)
{
@ -426,6 +548,15 @@ static int check_for_req_inflight(struct rsc_drv *drv, struct tcs_group *tcs,
return 0;
}
/**
* find_free_tcs() - Find free tcs in the given tcs_group; only for active.
* @tcs: A pointer to the active-only tcs_group (or the wake tcs_group if
* we borrowed it because there are zero active-only ones).
*
* Must be called with the drv->lock held since that protects tcs_in_use.
*
* Return: The first tcs that's free.
*/
static int find_free_tcs(struct tcs_group *tcs)
{
int i;
@ -438,6 +569,20 @@ static int find_free_tcs(struct tcs_group *tcs)
return -EBUSY;
}
/**
* tcs_write() - Store messages into a TCS right now, or return -EBUSY.
* @drv: The controller.
* @msg: The data to be sent.
*
* Grabs a TCS for ACTIVE_ONLY transfers and writes the messages to it.
*
* If there are no free TCSes for ACTIVE_ONLY transfers or if a command for
* the same address is already transferring returns -EBUSY which means the
* client should retry shortly.
*
* Return: 0 on success, -EBUSY if client should retry, or an error.
* Client should have interrupts enabled for a bit before retrying.
*/
static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
{
struct tcs_group *tcs;
@ -491,14 +636,26 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
}
/**
* rpmh_rsc_send_data: Validate the incoming message and write to the
* appropriate TCS block.
* rpmh_rsc_send_data() - Validate the incoming message + write to TCS block.
* @drv: The controller.
* @msg: The data to be sent.
*
* @drv: the controller
* @msg: the data to be sent
* NOTES:
* - This is only used for "ACTIVE_ONLY" since the limitations of this
* function don't make sense for sleep/wake cases.
* - To do the transfer, we will grab a whole TCS for ourselves--we don't
* try to share. If there are none available we'll wait indefinitely
* for a free one.
* - This function will not wait for the commands to be finished, only for
* data to be programmed into the RPMh. See rpmh_tx_done() which will
* be called when the transfer is fully complete.
* - This function must be called with interrupts enabled. If the hardware
* is busy doing someone else's transfer we need that transfer to fully
* finish so that we can have the hardware, and to fully finish it needs
* the interrupt handler to run. If the interrupts is set to run on the
* active CPU this can never happen if interrupts are disabled.
*
* Return: 0 on success, -EINVAL on error.
* Note: This call blocks until a valid data is written to the TCS.
*/
int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
{
@ -522,13 +679,30 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
return ret;
}
/**
* find_slots() - Find a place to write the given message.
* @tcs: The tcs group to search.
* @msg: The message we want to find room for.
* @tcs_id: If we return 0 from the function, we return the global ID of the
* TCS to write to here.
* @cmd_id: If we return 0 from the function, we return the index of
* the command array of the returned TCS where the client should
* start writing the message.
*
* Only for use on sleep/wake TCSes since those are the only ones we maintain
* tcs->slots for.
*
* Must be called with the tcs_lock for the group held.
*
* Return: -ENOMEM if there was no room, else 0.
*/
static int find_slots(struct tcs_group *tcs, const struct tcs_request *msg,
int *tcs_id, int *cmd_id)
{
int slot, offset;
int i = 0;
/* Do over, until we can fit the full payload in a TCS */
/* Do over, until we can fit the full payload in a single TCS */
do {
slot = bitmap_find_next_zero_area(tcs->slots, MAX_TCS_SLOTS,
i, msg->num_cmds, 0);
@ -547,12 +721,14 @@ static int find_slots(struct tcs_group *tcs, const struct tcs_request *msg,
}
/**
* rpmh_rsc_write_ctrl_data: Write request to the controller
* rpmh_rsc_write_ctrl_data() - Write request to controller but don't trigger.
* @drv: The controller.
* @msg: The data to be written to the controller.
*
* @drv: the controller
* @msg: the data to be written to the controller
* This should only be called for for sleep/wake state, never active-only
* state.
*
* There is no response returned for writing the request to the controller.
* Return: 0 if no error; else -error.
*/
int rpmh_rsc_write_ctrl_data(struct rsc_drv *drv, const struct tcs_request *msg)
{
@ -587,7 +763,6 @@ int rpmh_rsc_write_ctrl_data(struct rsc_drv *drv, const struct tcs_request *msg)
/**
* rpmh_rsc_ctrlr_is_busy() - Check if any of the AMCs are busy.
*
* @drv: The controller
*
* Checks if any of the AMCs are busy in handling ACTIVE sets.
@ -624,6 +799,23 @@ static bool rpmh_rsc_ctrlr_is_busy(struct rsc_drv *drv)
return false;
}
/**
* rpmh_rsc_cpu_pm_callback() - Check if any of the AMCs are busy.
* @nfb: Pointer to the notifier block in struct rsc_drv.
* @action: CPU_PM_ENTER, CPU_PM_ENTER_FAILED, or CPU_PM_EXIT.
* @v: Unused
*
* This function is given to cpu_pm_register_notifier so we can be informed
* about when CPUs go down. When all CPUs go down we know no more active
* transfers will be started so we write sleep/wake sets. This function gets
* called from cpuidle code paths and also at system suspend time.
*
* If its last CPU going down and AMCs are not busy then writes cached sleep
* and wake messages to TCSes. The firmware then takes care of triggering
* them when entering deepest low power modes.
*
* Return: See cpu_pm_register_notifier()
*/
static int rpmh_rsc_cpu_pm_callback(struct notifier_block *nfb,
unsigned long action, void *v)
{