Re: [PATCH v4 1/3] firmware: qcom_scm-64: Add atomic version of qcom_scm_call

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Hi Stephen,

On 2019-09-06 20:42, Stephen Boyd wrote:
Quoting Vivek Gautam (2019-08-22 23:32:46)
There are scnenarios where drivers are required to make a
scm call in atomic context, such as in one of the qcom's
arm-smmu-500 errata [1].

[1] ("https://source.codeaurora.org/quic/la/kernel/msm-4.9/
      tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4842")

Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
drivers/firmware/qcom_scm-64.c | 136 ++++++++++++++++++++++++++++-------------
 1 file changed, 92 insertions(+), 44 deletions(-)

diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
index 91d5ad7cf58b..b6dca32c5ac4 100644
--- a/drivers/firmware/qcom_scm-64.c
+++ b/drivers/firmware/qcom_scm-64.c
@@ -62,32 +62,71 @@ static DEFINE_MUTEX(qcom_scm_lock);
 #define FIRST_EXT_ARG_IDX 3
 #define N_REGISTER_ARGS (MAX_QCOM_SCM_ARGS - N_EXT_QCOM_SCM_ARGS + 1)

-/**
- * qcom_scm_call() - Invoke a syscall in the secure world
- * @dev:       device
- * @svc_id:    service identifier
- * @cmd_id:    command identifier
- * @desc: Descriptor structure containing arguments and return values
- *
- * Sends a command to the SCM and waits for the command to finish processing.
- * This should *only* be called in pre-emptible context.
-*/
-static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
-                        const struct qcom_scm_desc *desc,
-                        struct arm_smccc_res *res)
+static void __qcom_scm_call_do(const struct qcom_scm_desc *desc,
+                              struct arm_smccc_res *res, u32 fn_id,
+                              u64 x5, u32 type)
+{
+       u64 cmd;
+ struct arm_smccc_quirk quirk = {.id = ARM_SMCCC_QUIRK_QCOM_A6};

Nitpick: Put spaces around braces please.

+
+       cmd = ARM_SMCCC_CALL_VAL(type, qcom_smccc_convention,
+                                ARM_SMCCC_OWNER_SIP, fn_id);
+
+       quirk.state.a6 = 0;
+
+       do {
+               arm_smccc_smc_quirk(cmd, desc->arginfo, desc->args[0],
+                                   desc->args[1], desc->args[2], x5,
+                                   quirk.state.a6, 0, res, &quirk);
+
+               if (res->a0 == QCOM_SCM_INTERRUPTED)
+                       cmd = res->a0;
+
+       } while (res->a0 == QCOM_SCM_INTERRUPTED);
+}
+
+static void qcom_scm_call_do(const struct qcom_scm_desc *desc,
+                            struct arm_smccc_res *res, u32 fn_id,
+                            u64 x5, bool atomic)
+{
+       int retry_count = 0;
+
+       if (!atomic) {
+               do {
+                       mutex_lock(&qcom_scm_lock);
+
+                       __qcom_scm_call_do(desc, res, fn_id, x5,
+                                          ARM_SMCCC_STD_CALL);
+
+                       mutex_unlock(&qcom_scm_lock);
+
+                       if (res->a0 == QCOM_SCM_V2_EBUSY) {
+ if (retry_count++ > QCOM_SCM_EBUSY_MAX_RETRY)
+                                       break;
+                               msleep(QCOM_SCM_EBUSY_WAIT_MS);
+                       }
+               }  while (res->a0 == QCOM_SCM_V2_EBUSY);
+       } else {
+ __qcom_scm_call_do(desc, res, fn_id, x5, ARM_SMCCC_FAST_CALL);
+       }

To save on some indentation maybe you could write it like:

	if (atomic) {
		__qcom_scm_call_do(..)
		return;
	}

	do {
		mutex_lock(..)
		...
	} while (..);

+}
+
+static int ___qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
+                           const struct qcom_scm_desc *desc,
+                           struct arm_smccc_res *res, bool atomic)
 {
        int arglen = desc->arginfo & 0xf;
-       int retry_count = 0, i;
+       int i;
        u32 fn_id = QCOM_SCM_FNID(svc_id, cmd_id);
-       u64 cmd, x5 = desc->args[FIRST_EXT_ARG_IDX];
+       u64 x5 = desc->args[FIRST_EXT_ARG_IDX];
        dma_addr_t args_phys = 0;
        void *args_virt = NULL;
        size_t alloc_len;
- struct arm_smccc_quirk quirk = {.id = ARM_SMCCC_QUIRK_QCOM_A6};
+       gfp_t flag = atomic ? GFP_ATOMIC : GFP_KERNEL;

        if (unlikely(arglen > N_REGISTER_ARGS)) {
                alloc_len = N_EXT_QCOM_SCM_ARGS * sizeof(u64);
- args_virt = kzalloc(PAGE_ALIGN(alloc_len), GFP_KERNEL);
+               args_virt = kzalloc(PAGE_ALIGN(alloc_len), flag);

                if (!args_virt)
                        return -ENOMEM;
@@ -156,6 +169,41 @@ static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
        return 0;
 }

+/**
+ * qcom_scm_call() - Invoke a syscall in the secure world
+ * @dev:       device
+ * @svc_id:    service identifier
+ * @cmd_id:    command identifier
+ * @desc: Descriptor structure containing arguments and return values
+ *
+ * Sends a command to the SCM and waits for the command to finish processing.
+ * This should *only* be called in pre-emptible context.

Add a might_sleep() then?

+ */
+static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
+                        const struct qcom_scm_desc *desc,
+                        struct arm_smccc_res *res)
+{
+ return ___qcom_scm_call(dev, svc_id, cmd_id, desc, res, false);
+}
+
+/**
+ * qcom_scm_call_atomic() - atomic variation of qcom_scm_call()
+ * @dev:       device
+ * @svc_id:    service identifier
+ * @cmd_id:    command identifier
+ * @desc: Descriptor structure containing arguments and return values
+ * @res:       Structure containing results from SMC/HVC call
+ *
+ * Sends a command to the SCM and waits for the command to finish processing.
+ * This should be called in atomic context only.

Maybe add a cant_sleep()?

+ */
+static int qcom_scm_call_atomic(struct device *dev, u32 svc_id, u32 cmd_id,
+                               const struct qcom_scm_desc *desc,
+                               struct arm_smccc_res *res)
+{
+       return ___qcom_scm_call(dev, svc_id, cmd_id, desc, res, true);
+}
+

Have addressed all your comments in v5.

Thanks,
Sai

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation



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