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From:   Guru Das Srinagesh <quic_gurus@quicinc.com>
To:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
CC:     David Heidelberg <david@ixit.cz>,
        Robert Marko <robimarko@gmail.com>,
        Rajendra Nayak <quic_rjendra@quicinc.com>,
        Elliot Berman <quic_eberman@quicinc.com>,
        Guru Das Srinagesh <quic_gurus@quicinc.com>
Subject: [PATCH v2 5/5] firmware: qcom: scm: Add wait-queue handling logic
Date:   Fri, 22 Jul 2022 15:37:18 -0700
Message-ID: <1658529438-9234-6-git-send-email-quic_gurus@quicinc.com>
In-Reply-To: <1658529438-9234-1-git-send-email-quic_gurus@quicinc.com>
References: <1658529438-9234-1-git-send-email-quic_gurus@quicinc.com>
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Add logic to handle QCOM_SCM_WAITQ_SLEEP or QCOM_SCM_WAITQ_WAKE return
codes.

Scenario 1: Requests made by 2 different VMs:

  VM_1                     VM_2                            Firmware
    │                        │                                 │
    │                        │                                 │
    │                        │                                 │
    │                        │                                 │
    │      REQUEST_1         │                                 │
    ├────────────────────────┼─────────────────────────────────┤
    │                        │                                 │
    │                        │                              ┌──┼──┐
    │                        │                              │  │  │
    │                        │     REQUEST_2                │  │  │
    │                        ├──────────────────────────────┼──┤  │
    │                        │                              │  │  │Resource
    │                        │                              │  │  │is busy
    │                        │       {WQ_SLEEP}             │  │  │
    │                        │◄─────────────────────────────┼──┤  │
    │                        │  wq_ctx, smc_call_ctx        │  │  │
    │                        │                              └──┼──┘
    │   REQUEST_1 COMPLETE   │                                 │
    │◄───────────────────────┼─────────────────────────────────┤
    │                        │                                 │
    │                        │         IRQ                     │
    │                        │◄─-------------------------------│
    │                        │                                 │
    │                        │      get_wq_ctx()               │
    │                        ├────────────────────────────────►│
    │                        │                                 │
    │                        │                                 │
    │                        │◄────────────────────────────────┤
    │                        │   wq_ctx, flags, and            │
    │                        │        more_pending             │
    │                        │                                 │
    │                        │                                 │
    │                        │ wq_resume(smc_call_ctx)         │
    │                        ├────────────────────────────────►│
    │                        │                                 │
    │                        │                                 │
    │                        │      REQUEST_2 COMPLETE         │
    │                        │◄────────────────────────────────┤
    │                        │                                 │
    │                        │                                 │

Scenario 2: Two Requests coming in from same VM:

  VM_1                                                     Firmware
    │                                                          │
    │                                                          │
    │                                                          │
    │                                                          │
    │      REQUEST_1                                           │
    ├──────────────────────────────────────────────────────────┤
    │                                                          │
    │                                                     ┌────┼───┐
    │                                                     │    │   │
    │                                                     │    │   │
    │                                                     │    │   │
    │      REQUEST_2                                      │    │   │
    ├─────────────────────────────────────────────────────┼───►│   │
    │                                                     │    │   │Resource
    │                                                     │    │   │is busy
    │      {WQ_SLEEP}                                     │    │   │
    │◄────────────────────────────────────────────────────┼────┤   │
    │      wq_ctx, req2_smc_call_ctx                      │    │   │
    │                                                     │    │   │
    │                                                     └────┼───┘
    │                                                          │
    │      {WQ_WAKE}                                           │
    │◄─────────────────────────────────────────────────────────┤
    │      wq_ctx, req1_smc_call_ctx, flags                    │
    │                                                          │
    │                                                          │
    │      wq_wake_ack(req1_smc_call_ctx)                      │
    ├─────────────────────────────────────────────────────────►│
    │                                                          │
    │      REQUEST_1 COMPLETE                                  │
    │◄─────────────────────────────────────────────────────────┤
    │                                                          │
    │                                                          │
    │      wq_resume(req_2_smc_call_ctx)                       │
    ├─────────────────────────────────────────────────────────►│
    │                                                          │
    │      REQUEST_2 COMPLETE                                  │
    │◄─────────────────────────────────────────────────────────┤
    │                                                          │

With the exception of get_wq_ctx(), the other two newly-introduced SMC
calls, wq_ack() and wq_resume() can themselves return WQ_SLEEP (these
nested rounds of WQ_SLEEP are not shown in the above diagram for the
sake of simplicity). Therefore, introduce a new do-while loop to handle
multiple WQ_SLEEP return values for the same parent SCM call.

Request Completion in the above diagram refers to either a success
return value (zero) or error (and not SMC_WAITQ_SLEEP or
SMC_WAITQ_WAKE).

Signed-off-by: Guru Das Srinagesh <quic_gurus@quicinc.com>
---
[v2]
- Combined the error and success cases in scm_smc_do_quirk().

 drivers/firmware/qcom_scm-smc.c | 76 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 69 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/qcom_scm-smc.c b/drivers/firmware/qcom_scm-smc.c
index 4150da1..09cca48 100644
--- a/drivers/firmware/qcom_scm-smc.c
+++ b/drivers/firmware/qcom_scm-smc.c
@@ -53,6 +53,9 @@ static void __scm_smc_do_quirk(const struct arm_smccc_args *smc,
 	} while (res->a0 == QCOM_SCM_INTERRUPTED);
 }
 
+#define IS_WAITQ_SLEEP_OR_WAKE(res) \
+	(res->a0 == QCOM_SCM_WAITQ_SLEEP || res->a0 == QCOM_SCM_WAITQ_WAKE)
+
 static void fill_wq_resume_args(struct arm_smccc_args *resume, u32 smc_call_ctx)
 {
 	memset(resume->args, 0, ARRAY_SIZE(resume->args));
@@ -109,25 +112,77 @@ int scm_get_wq_ctx(u32 *wq_ctx, u32 *flags, u32 *more_pending)
 	return 0;
 }
 
-static void __scm_smc_do(const struct arm_smccc_args *smc,
+static int scm_smc_do_quirk(struct device *dev, struct arm_smccc_args *smc,
+			    struct arm_smccc_res *res)
+{
+	struct completion *wq = NULL;
+	struct qcom_scm *qscm;
+	u32 wq_ctx, smc_call_ctx, flags;
+
+	do {
+		__scm_smc_do_quirk(smc, res);
+
+		if (IS_WAITQ_SLEEP_OR_WAKE(res)) {
+			wq_ctx = res->a1;
+			smc_call_ctx = res->a2;
+			flags = res->a3;
+
+			if (!dev)
+				return -EPROBE_DEFER;
+
+			qscm = dev_get_drvdata(dev);
+			wq = qcom_scm_lookup_wq(qscm, wq_ctx);
+			if (IS_ERR_OR_NULL(wq)) {
+				pr_err("No waitqueue found for wq_ctx %d: %ld\n",
+						wq_ctx, PTR_ERR(wq));
+				return PTR_ERR(wq);
+			}
+
+			if (res->a0 == QCOM_SCM_WAITQ_SLEEP) {
+				wait_for_completion(wq);
+				fill_wq_resume_args(smc, smc_call_ctx);
+				wq = NULL;
+				continue;
+			} else {
+				fill_wq_wake_ack_args(smc, smc_call_ctx);
+				continue;
+			}
+		} else if (!res->a0 || (long)res->a0 < 0) {
+			/*
+			 * Success, or error.
+			 * wq will be set only if a prior WAKE happened.
+			 * Its value will be the one from the prior WAKE.
+			 */
+			if (wq)
+				scm_waitq_flag_handler(wq, flags);
+			break;
+		}
+	} while (IS_WAITQ_SLEEP_OR_WAKE(res));
+
+	return 0;
+}
+
+static int __scm_smc_do(struct device *dev, struct arm_smccc_args *smc,
 			 struct arm_smccc_res *res, bool atomic)
 {
-	int retry_count = 0;
+	int ret, retry_count = 0;
 
 	if (atomic) {
 		__scm_smc_do_quirk(smc, res);
-		return;
+		return 0;
 	}
 
 	do {
 		if (!qcom_scm_allow_multicall)
 			mutex_lock(&qcom_scm_lock);
 
-		__scm_smc_do_quirk(smc, res);
+		ret = scm_smc_do_quirk(dev, smc, res);
 
 		if (!qcom_scm_allow_multicall)
 			mutex_unlock(&qcom_scm_lock);
 
+		if (ret)
+			return ret;
 
 		if (res->a0 == QCOM_SCM_V2_EBUSY) {
 			if (retry_count++ > QCOM_SCM_EBUSY_MAX_RETRY)
@@ -135,6 +190,8 @@ static void __scm_smc_do(const struct arm_smccc_args *smc,
 			msleep(QCOM_SCM_EBUSY_WAIT_MS);
 		}
 	}  while (res->a0 == QCOM_SCM_V2_EBUSY);
+
+	return 0;
 }
 
 
@@ -143,7 +200,7 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc,
 		   struct qcom_scm_res *res, bool atomic)
 {
 	int arglen = desc->arginfo & 0xf;
-	int i;
+	int i, ret;
 	dma_addr_t args_phys = 0;
 	void *args_virt = NULL;
 	size_t alloc_len;
@@ -195,19 +252,24 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc,
 		smc.args[SCM_SMC_LAST_REG_IDX] = args_phys;
 	}
 
-	__scm_smc_do(&smc, &smc_res, atomic);
+	ret = __scm_smc_do(dev, &smc, &smc_res, atomic);
+	/* ret error check follows after args_virt cleanup*/
 
 	if (args_virt) {
 		dma_unmap_single(dev, args_phys, alloc_len, DMA_TO_DEVICE);
 		kfree(args_virt);
 	}
 
+	if (ret)
+		return ret;
+
 	if (res) {
 		res->result[0] = smc_res.a1;
 		res->result[1] = smc_res.a2;
 		res->result[2] = smc_res.a3;
 	}
 
-	return (long)smc_res.a0 ? qcom_scm_remap_error(smc_res.a0) : 0;
+	ret = (long)smc_res.a0 ? qcom_scm_remap_error(smc_res.a0) : 0;
 
+	return ret;
 }
-- 
2.7.4