From patchwork Wed Mar 11 23:13:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 11433055 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7E0D013B1 for ; Wed, 11 Mar 2020 23:14:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0674420751 for ; Wed, 11 Mar 2020 23:14:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="OuQIIP/D" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731502AbgCKXOo (ORCPT ); Wed, 11 Mar 2020 19:14:44 -0400 Received: from mail-pg1-f174.google.com ([209.85.215.174]:44881 "EHLO mail-pg1-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731488AbgCKXOV (ORCPT ); Wed, 11 Mar 2020 19:14:21 -0400 Received: by mail-pg1-f174.google.com with SMTP id 37so2012697pgm.11 for ; Wed, 11 Mar 2020 16:14:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=NaNAdzL2XEfcvjYu5mo/uVEx+JASRSRpLwar1oYdQ5M=; b=OuQIIP/Dm1fv4rd0kw0c5G9svnZZ1Th9xVsAoLnt/knYbLg8d12TIZTSIU6bvGTMX1 Y7dkbg+ujvEFSItl8RiRCbcZjuv0OYvM4vYogod7Uq9kGIk6cLWmB/UZJRgO5kbPQQnw QPQdb/XMNYRa/slyYDP1xedZJE8v/RRwZiMYM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=NaNAdzL2XEfcvjYu5mo/uVEx+JASRSRpLwar1oYdQ5M=; b=LByqz8f/C3q1ib0f/3k+y+S3263VpP3xU5pTqlG43TD484MqNFx4wkZPnksxwxKzYg gk7Gha307FjgY5BY7dSmYTNZWAgzjTklWc8yDiUImKfm+4dCwdvv8dXmnc3J7lfuuUrS 8sgkbuos3P7sim02/jzhKCjQgulI19hYj6/GZ/cT4qDBPIPULCWSXOcpnt6XXxCH2ntv CIK2wHL7Ta4zVNAR3Y3/gR1qgkWZAOLP2II9zdO/3SRnsMLgpU6CFsKsnggeH3IiWZQp Ci0wZAbBwOiYw1CTVj3wcbvDB3OXTV934LXFfACXngPGDn3dgO2oTqEB2tiPDKUxuCbC t4Og== X-Gm-Message-State: ANhLgQ1q6UeAw5Sfs/XUTq1bF5oC6vC5JB5+fLzy/rwMQAGGa8Y2+Kcd bV7xvZQCACUWa8w53Rj2Zf7lvA== X-Google-Smtp-Source: ADFU+vuAZaEjcG8pGAg04HxVBKzMuundPylxaarEWc/ti/6gjDutaCHrApU/XeNcmVrg0CxEvQt3gA== X-Received: by 2002:a63:b949:: with SMTP id v9mr4801566pgo.336.1583968458318; Wed, 11 Mar 2020 16:14:18 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:24fa:e766:52c9:e3b2]) by smtp.gmail.com with ESMTPSA id g75sm2606334pje.37.2020.03.11.16.14.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2020 16:14:17 -0700 (PDT) From: Douglas Anderson To: Andy Gross , Bjorn Andersson , Maulik Shah Cc: mka@chromium.org, Rajendra Nayak , evgreen@chromium.org, Lina Iyer , swboyd@chromium.org, Douglas Anderson , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFT PATCH v2 05/10] drivers: qcom: rpmh-rsc: A lot of comments Date: Wed, 11 Mar 2020 16:13:43 -0700 Message-Id: <20200311161104.RFT.v2.5.I52653eb85d7dc8981ee0dafcd0b6cc0f273e9425@changeid> X-Mailer: git-send-email 2.25.1.481.gfbce0eb801-goog In-Reply-To: <20200311231348.129254-1-dianders@chromium.org> References: <20200311231348.129254-1-dianders@chromium.org> MIME-Version: 1.0 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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. This should be a no-op. It's just comment changes. Signed-off-by: Douglas Anderson --- Changes in v2: - More clear that active-only xfers can happen on wake TCS sometimes. - Document locks for updating "tcs_in_use" more. - Document tcs_is_free() without drv->lock OK for tcs_invalidate(). - Document bug of tcs_write() not handling -EAGAIN. - Document get_tcs_for_msg() => -EAGAIN only for ACTIVE_ONLY. - Reword tcs_write() doc a bit. - Document two get_tcs_for_msg() issues if zero-active TCS. - Document that rpmh_rsc_send_data() can be an implicit invalidate. - Fixed documentation of "tcs" param in find_slots(). drivers/soc/qcom/rpmh-internal.h | 52 +++--- drivers/soc/qcom/rpmh-rsc.c | 264 +++++++++++++++++++++++++++++-- 2 files changed, 281 insertions(+), 35 deletions(-) diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h index 6eec32b97f83..b756d3036e96 100644 --- a/drivers/soc/qcom/rpmh-internal.h +++ b/drivers/soc/qcom/rpmh-internal.h @@ -22,16 +22,25 @@ 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 - * @cmd_cache: flattened cache of cmds in sleep/wake 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 + * @cmd_cache: Flattened cache of cmds in sleep/wake TCS; num_tcs * ncpt big. + * @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; @@ -84,14 +93,21 @@ 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 - * @tcs: TCS groups - * @tcs_in_use: s/w state of the TCS - * @lock: synchronize state of the controller - * @client: handle to the DRV's client. + * @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. + * @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 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. + * @client: Handle to the DRV's client. */ struct rsc_drv { const char *name; diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c index c9f29cbd5ee5..9d2669cbd994 100644 --- a/drivers/soc/qcom/rpmh-rsc.c +++ b/drivers/soc/qcom/rpmh-rsc.c @@ -164,12 +164,38 @@ 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. + * + * 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 TCSs 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; @@ -196,9 +222,11 @@ 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) { @@ -211,6 +239,20 @@ 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 TCSs. + * + * Called without drv->lock held and with no tcs_lock locks held. + * + * 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. + * Only ever returns -EAGAIN for ACTIVE_ONLY transfers. + */ static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv, const struct tcs_request *msg) { @@ -246,12 +288,35 @@ static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv, ret = rpmh_rsc_invalidate(drv); if (ret) return ERR_PTR(ret); + + /* + * TODO: + * - Temporarily enable IRQs on the wake tcs. + * - Make sure nobody else race with us and re-write + * to this TCS; document how this works. + */ } } 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) { @@ -268,7 +333,14 @@ static const struct tcs_request *get_req_from_tcs(struct rsc_drv *drv, } /** - * 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 TCSs (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) { @@ -278,6 +350,7 @@ static irqreturn_t tcs_tx_done(int irq, void *p) const struct tcs_request *req; struct tcs_cmd *cmd; + /* NOTE: interrupt status for all TCSs are found in TCS 0 */ irq_status = read_tcs_reg(drv, RSC_DRV_IRQ_STATUS, 0); for_each_set_bit(i, &irq_status, BITS_PER_LONG) { @@ -318,6 +391,16 @@ 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 TCSs (active, sleep, and wake). + */ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id, const struct tcs_request *msg) { @@ -351,6 +434,15 @@ 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); } +/** + * __tcs_trigger() - Start transferring on the given TCS. + * + * The TCS given is probably the active-only one, but could be a wake one + * that we borrowed if there are zero active-only TCSs. + * + * @drv: The controller. + * @tcs_id: The global ID of this TCS. + */ static void __tcs_trigger(struct rsc_drv *drv, int tcs_id) { u32 enable; @@ -373,6 +465,27 @@ static void __tcs_trigger(struct rsc_drv *drv, int tcs_id) write_tcs_reg_sync(drv, RSC_DRV_CONTROL, tcs_id, 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). + * + * Only for use for ACTIVE_ONLY tcs_group, since those are the only ones + * that might be actively sending. + * + * This will walk through the TCSs 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. + * + * 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) { @@ -399,6 +512,15 @@ 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_ONLY. + * @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; @@ -411,6 +533,20 @@ 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 ACTIVE_ONLY TCSs 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; @@ -418,16 +554,14 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg) unsigned long flags; int ret; + /* TODO: get_tcs_for_msg() can return -EAGAIN and nobody handles */ tcs = get_tcs_for_msg(drv, msg); if (IS_ERR(tcs)) return PTR_ERR(tcs); spin_lock_irqsave(&tcs->lock, flags); + spin_lock(&drv->lock); - /* - * The h/w does not like if we send a request to the same address, - * when one is already in-flight or being processed. - */ ret = check_for_req_inflight(drv, tcs, msg); if (ret) { spin_unlock(&drv->lock); @@ -454,14 +588,30 @@ 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. + * - If there are no active TCS calling this function can cause an implicit + * call to rpmh_rsc_invalidate(). Unless you know for sure that you have + * an active TCS you should assume that you need to re-write sleep/wake + * values after calling this function. * * 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) { @@ -485,6 +635,63 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg) return ret; } +/** + * find_match() - Find if the cmd sequence is in the tcs_group + * @tcs: The tcs_group to search. Either sleep or wake. + * @cmd: The command sequence to search for; only addr is looked at. + * @len: The number of commands in the sequence. + * + * Searches through the given tcs_group to see if a given command sequence + * is in there. + * + * Two sequences are matches if they modify the same set of addresses in + * the same order. The value of the data is not considered when deciding if + * two things are matches. + * + * How this function works is best understood by example. For our example, + * we'll imagine our tcs group contains these (cmd, data) tuples: + * [(a, A), (b, B), (c, C), (d, D), (e, E), (f, F), (g, G), (h, H)] + * ...in other words it has an element where (addr=a, data=A), etc. + * ...we'll assume that there is one TCS in the group that can store 8 commands. + * + * - find_match([(a, X)]) => 0 + * - find_match([(c, X), (d, X)]) => 2 + * - find_match([(c, X), (d, X), (e, X)]) => 2 + * - find_match([(z, X)]) => -ENODATA + * - find_match([(a, X), (y, X)]) => -EINVAL (and warning printed) + * - find_match([(g, X), (h, X), (i, X)]) => -EINVAL (and warning printed) + * - find_match([(y, X), (a, X)]) => -ENODATA + * + * NOTE: This function overall seems like it has questionable value. + * - It can be used to update a message in the TCS with new data, but I + * don't believe we actually do that--we always fully invalidate and + * re-write everything. Specifically it would be too limiting to force + * someone not to change the set of addresses written to each time. + * - This function could be attempting to avoid writing different data to + * the same address twice in a tcs_group. If that's the goal, it doesn't + * do a great job since find_match([(y, X), (a, X)]) return -ENODATA in my + * above example. + * - If you originally wrote [(a, A), (b, B), (c, C)] and later tried to + * write [(a, A), (b, B)] it'd look like a match and we wouldn't consider + * it an error that the size got shorter. + * - If two clients wrote sequences that happened to be placed in slots next + * to each other then a later check could match a sequence that was the + * size of both together. + * + * TODO: in light of the above, prehaps we can just remove this function? + * If we later come up with fancy algorithms for updating everything without + * full invalidations we can come up with something then. + * + * Only for use on sleep/wake TCSs since those are the only ones we maintain + * tcs->slots and tcs->cmd_cache for. + * + * Must be called with the tcs_lock for the group held. + * + * Return: If the given command sequence wasn't in the tcs_group: -ENODATA. + * If the given command sequence was in the tcs_group: the index of + * the slot in the tcs_group where the first command is. + * In some error cases (see above), -EINVAL. + */ static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd, int len) { @@ -497,6 +704,11 @@ static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd, if (i + len >= tcs->num_tcs * tcs->ncpt) goto seq_err; for (j = 0; j < len; j++) { + /* + * TODO: it's actually not valid to look at + * "cmd_cache[x]" if "slots[x]" doesn't have a bit + * set. Should add a check. + */ if (tcs->cmd_cache[i + j] != cmd[j].addr) goto seq_err; } @@ -510,6 +722,23 @@ static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd, return -EINVAL; } +/** + * 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 TCSs since those are the only ones we maintain + * tcs->slots and tcs->cmd_cache 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) { @@ -521,7 +750,7 @@ static int find_slots(struct tcs_group *tcs, const struct tcs_request *msg, if (slot >= 0) goto copy_data; - /* 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); @@ -544,12 +773,13 @@ static int find_slots(struct tcs_group *tcs, const struct tcs_request *msg, } /** - * rpmh_rsc_write_ctrl_data: Write request to the controller - * - * @drv: the controller - * @msg: the data to be written 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. * * 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) {