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References: <20210609060910.1500481-1-jens.wiklander@linaro.org> <20210609060910.1500481-5-jens.wiklander@linaro.org>
In-Reply-To: <20210609060910.1500481-5-jens.wiklander@linaro.org>
From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Wed, 9 Jun 2021 09:02:19 +0200
Message-ID: <CAMj1kXGP=ZzVNTYZ3zuUS6G8wmbiu1f52nxmXk8QWeFgvXhBeA@mail.gmail.com>
Subject: Re: [PATCH 4/4] optee: add asynchronous notifications
To:     Jens Wiklander <jens.wiklander@linaro.org>,
        Marc Zyngier <maz@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        op-tee@lists.trustedfirmware.org,
        Jerome Forissier <jerome@forissier.org>,
        Etienne Carriere <etienne.carriere@linaro.org>,
        Sumit Garg <sumit.garg@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>
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Precedence: bulk

(+ Marc)

Hi Jens,

On Wed, 9 Jun 2021 at 08:11, Jens Wiklander <jens.wiklander@linaro.org> wrote:
>
> Adds support for asynchronous notifications from secure world to normal
> world. This allows a design with a top half and bottom half type of
> driver where the top half runs in secure interrupt context and a
> notifications tells normal world to schedule a yielding call to do the
> bottom half processing.
>
> The protocol is defined in optee_msg.h optee_rpc_cmd.h and optee_smc.h.
>
> A notification consists of a 32-bit value which normal world can
> retrieve using a fastcall into secure world. The value
> OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF (0) has a special meaning.
> When this value is sent it means that normal world is supposed to make a
> yielding call OPTEE_MSG_CMD_DO_BOTTOM_HALF.
>
> Notification capability is negotiated while the driver is initialized.
> If both sides supports these notifications then they are enabled.
>
> A SPI interrupt is used to notify the driver that there are asynchronous
> notifications pending.

Wouldn't it be better for this interrupt to be described using DT or
ACPI, and use the normal IRQ request API, rather than putting GIC
specifics into this driver?

E.g., SynQuacer has a EXIU interrupt block that sits before the GIC,
and would probably be more suitable for delivering secure-to-normal
world software interrupts in this way, but I don't think your current
design would support that.


> The interrupt number is transmitted during
> capability exchange. The maximum needed notification value is also
> communicated at this stage. This allows scaling up when needed.
>
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> ---
>  drivers/tee/optee/call.c          |  27 ++++++++
>  drivers/tee/optee/core.c          |  99 ++++++++++++++++++++-------
>  drivers/tee/optee/notif.c         | 109 ++++++++++++++++++++++++++++--
>  drivers/tee/optee/optee_msg.h     |   9 +++
>  drivers/tee/optee/optee_private.h |   6 +-
>  drivers/tee/optee/optee_smc.h     |  79 +++++++++++++++++++++-
>  6 files changed, 296 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
> index 6132cc8d014c..9da66acac828 100644
> --- a/drivers/tee/optee/call.c
> +++ b/drivers/tee/optee/call.c
> @@ -390,6 +390,33 @@ int optee_cancel_req(struct tee_context *ctx, u32 cancel_id, u32 session)
>         return 0;
>  }
>
> +static int simple_call_with_arg(struct tee_context *ctx, u32 cmd)
> +{
> +       struct optee_msg_arg *msg_arg;
> +       phys_addr_t msg_parg;
> +       struct tee_shm *shm;
> +
> +       shm = get_msg_arg(ctx, 0, &msg_arg, &msg_parg);
> +       if (IS_ERR(shm))
> +               return PTR_ERR(shm);
> +
> +       msg_arg->cmd = cmd;
> +       optee_do_call_with_arg(ctx, msg_parg);
> +
> +       tee_shm_free(shm);
> +       return 0;
> +}
> +
> +int optee_do_bottom_half(struct tee_context *ctx)
> +{
> +       return simple_call_with_arg(ctx, OPTEE_MSG_CMD_DO_BOTTOM_HALF);
> +}
> +
> +int optee_stop_async_notif(struct tee_context *ctx)
> +{
> +       return simple_call_with_arg(ctx, OPTEE_MSG_CMD_STOP_ASYNC_NOTIF);
> +}
> +
>  /**
>   * optee_enable_shm_cache() - Enables caching of some shared memory allocation
>   *                           in OP-TEE
> diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
> index 2272696ac986..86eb72dc9a00 100644
> --- a/drivers/tee/optee/core.c
> +++ b/drivers/tee/optee/core.c
> @@ -7,9 +7,12 @@
>
>  #include <linux/arm-smccc.h>
>  #include <linux/errno.h>
> +#include <linux/interrupt.h>
>  #include <linux/io.h>
> +#include <linux/irqdomain.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_irq.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> @@ -353,6 +356,17 @@ static const struct tee_desc optee_supp_desc = {
>         .flags = TEE_DESC_PRIVILEGED,
>  };
>
> +static int enable_async_notif(optee_invoke_fn *invoke_fn)
> +{
> +       struct arm_smccc_res res;
> +
> +       invoke_fn(OPTEE_SMC_ENABLE_ASYNC_NOTIF, 0, 0, 0, 0, 0, 0, 0, &res);
> +
> +       if (res.a0)
> +               return -EINVAL;
> +       return 0;
> +}
> +
>  static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
>  {
>         struct arm_smccc_res res;
> @@ -402,7 +416,8 @@ static bool optee_msg_api_revision_is_compatible(optee_invoke_fn *invoke_fn)
>  }
>
>  static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
> -                                           u32 *sec_caps)
> +                                           u32 *sec_caps, u16 *notif_intid,
> +                                           u32 *max_notif_value)
>  {
>         union {
>                 struct arm_smccc_res smccc;
> @@ -425,6 +440,8 @@ static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
>                 return false;
>
>         *sec_caps = res.result.capabilities;
> +       *notif_intid = res.result.data0 & 0xffff;
> +       *max_notif_value = res.result.max_notif_value;
>         return true;
>  }
>
> @@ -609,6 +626,8 @@ static int optee_probe(struct platform_device *pdev)
>         struct optee *optee = NULL;
>         void *memremaped_shm = NULL;
>         struct tee_device *teedev;
> +       u32 max_notif_value;
> +       u16 notif_intid;
>         u32 sec_caps;
>         int rc;
>
> @@ -628,7 +647,8 @@ static int optee_probe(struct platform_device *pdev)
>                 return -EINVAL;
>         }
>
> -       if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps)) {
> +       if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps,
> +                                            &notif_intid, &max_notif_value)) {
>                 pr_warn("capabilities mismatch\n");
>                 return -EINVAL;
>         }
> @@ -651,7 +671,7 @@ static int optee_probe(struct platform_device *pdev)
>         optee = kzalloc(sizeof(*optee), GFP_KERNEL);
>         if (!optee) {
>                 rc = -ENOMEM;
> -               goto err;
> +               goto err_free_pool;
>         }
>
>         optee->invoke_fn = invoke_fn;
> @@ -660,24 +680,24 @@ static int optee_probe(struct platform_device *pdev)
>         teedev = tee_device_alloc(&optee_desc, NULL, pool, optee);
>         if (IS_ERR(teedev)) {
>                 rc = PTR_ERR(teedev);
> -               goto err;
> +               goto err_free_optee;
>         }
>         optee->teedev = teedev;
>
>         teedev = tee_device_alloc(&optee_supp_desc, NULL, pool, optee);
>         if (IS_ERR(teedev)) {
>                 rc = PTR_ERR(teedev);
> -               goto err;
> +               goto err_unreg_teedev;
>         }
>         optee->supp_teedev = teedev;
>
>         rc = tee_device_register(optee->teedev);
>         if (rc)
> -               goto err;
> +               goto err_unreg_supp_teedev;
>
>         rc = tee_device_register(optee->supp_teedev);
>         if (rc)
> -               goto err;
> +               goto err_unreg_supp_teedev;
>
>         mutex_init(&optee->call_queue.mutex);
>         INIT_LIST_HEAD(&optee->call_queue.waiters);
> @@ -687,10 +707,44 @@ static int optee_probe(struct platform_device *pdev)
>
>         platform_set_drvdata(pdev, optee);
>
> -       rc = optee_notif_init(optee, 255);
> -       if (rc) {
> -               optee_remove(pdev);
> -               return rc;
> +       if (sec_caps & OPTEE_SMC_SEC_CAP_ASYNC_NOTIF) {
> +               const unsigned int spi_base = 32;
> +               struct irq_fwspec fwspec;
> +               struct device_node *np;
> +               unsigned int irq;
> +
> +               if (notif_intid < spi_base) {
> +                       rc = -EINVAL;
> +                       goto err_unreg_supp_teedev;
> +               }
> +
> +               np = of_irq_find_parent(pdev->dev.of_node);
> +               fwspec.fwnode = of_node_to_fwnode(np);
> +               fwspec.param_count = 3;
> +               fwspec.param[0] = 0; /* SPI */
> +               fwspec.param[1] = notif_intid - spi_base;
> +               fwspec.param[2] = IRQ_TYPE_LEVEL_HIGH;
> +
> +               irq = irq_create_fwspec_mapping(&fwspec);
> +               if (!irq) {
> +                       rc = -EINVAL;
> +                       goto err_unreg_supp_teedev;
> +               }
> +
> +               rc = optee_notif_init(optee, max_notif_value, irq);
> +               if (rc) {
> +                       irq_dispose_mapping(irq);
> +                       optee_remove(pdev);
> +                       return rc;
> +               }
> +               enable_async_notif(optee->invoke_fn);
> +               pr_info("Asynchronous notifications enabled\n");
> +       } else {
> +               rc = optee_notif_init(optee, 255, 0);
> +               if (rc) {
> +                       optee_remove(pdev);
> +                       return rc;
> +               }
>         }
>
>         optee_enable_shm_cache(optee);
> @@ -706,20 +760,15 @@ static int optee_probe(struct platform_device *pdev)
>
>         pr_info("initialized driver\n");
>         return 0;
> -err:
> -       if (optee) {
> -               /*
> -                * tee_device_unregister() is safe to call even if the
> -                * devices hasn't been registered with
> -                * tee_device_register() yet.
> -                */
> -               tee_device_unregister(optee->supp_teedev);
> -               tee_device_unregister(optee->teedev);
> -               kfree(optee);
> -       }
> -       if (pool)
> -               tee_shm_pool_free(pool);
> -       if (memremaped_shm)
> +err_unreg_supp_teedev:
> +       tee_device_unregister(optee->supp_teedev);
> +err_unreg_teedev:
> +       tee_device_unregister(optee->teedev);
> +err_free_optee:
> +       kfree(optee);
> +err_free_pool:
> +       tee_shm_pool_free(pool);
> +       if (optee->memremaped_shm)
>                 memunmap(memremaped_shm);
>         return rc;
>  }
> diff --git a/drivers/tee/optee/notif.c b/drivers/tee/optee/notif.c
> index a28fa03dcd0e..ecfa82797695 100644
> --- a/drivers/tee/optee/notif.c
> +++ b/drivers/tee/optee/notif.c
> @@ -7,10 +7,14 @@
>
>  #include <linux/arm-smccc.h>
>  #include <linux/errno.h>
> +#include <linux/interrupt.h>
> +#include <linux/irqdomain.h>
>  #include <linux/slab.h>
>  #include <linux/spinlock.h>
>  #include <linux/tee_drv.h>
>  #include "optee_private.h"
> +#include "optee_smc.h"
> +#include "optee_rpc_cmd.h"
>
>  struct notif_entry {
>         struct list_head link;
> @@ -18,6 +22,54 @@ struct notif_entry {
>         u_int key;
>  };
>
> +static u32 get_async_notif_value(optee_invoke_fn *invoke_fn, bool *value_valid,
> +                                bool *value_pending)
> +{
> +       struct arm_smccc_res res;
> +
> +       invoke_fn(OPTEE_SMC_GET_ASYNC_NOTIF_VALUE, 0, 0, 0, 0, 0, 0, 0, &res);
> +
> +       if (res.a0)
> +               return 0;
> +       *value_valid = (res.a2 & OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID);
> +       *value_pending = (res.a2 & OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING);
> +       return res.a1;
> +}
> +
> +static irqreturn_t notif_irq_handler(int irq, void *dev_id)
> +{
> +       struct optee *optee = dev_id;
> +       bool do_bottom_half = false;
> +       bool value_valid;
> +       bool value_pending;
> +       u32 value;
> +
> +       do {
> +               value = get_async_notif_value(optee->invoke_fn, &value_valid,
> +                                             &value_pending);
> +               if (!value_valid)
> +                       break;
> +
> +               if (value == OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF)
> +                       do_bottom_half = true;
> +               else
> +                       optee_notif_send(optee, value);
> +       } while (value_pending);
> +
> +       if (do_bottom_half)
> +               return IRQ_WAKE_THREAD;
> +       return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t notif_irq_thread_fn(int irq, void *dev_id)
> +{
> +       struct optee *optee = dev_id;
> +
> +       optee_do_bottom_half(optee->notif.ctx);
> +
> +       return IRQ_HANDLED;
> +}
> +
>  static bool have_key(struct optee *optee, u_int key)
>  {
>         struct notif_entry *entry;
> @@ -106,20 +158,69 @@ int optee_notif_send(struct optee *optee, u_int key)
>         return 0;
>  }
>
> -int optee_notif_init(struct optee *optee, u_int max_key)
> +int optee_notif_init(struct optee *optee, u_int max_key, u_int irq)
>  {
> +       struct tee_context *ctx;
> +       int rc;
> +
> +       if (irq) {
> +               ctx = tee_dev_open_helper(optee->teedev);
> +               if (IS_ERR(ctx))
> +                       return PTR_ERR(ctx);
> +
> +               optee->notif.ctx = ctx;
> +       }
> +
>         spin_lock_init(&optee->notif.lock);
>         INIT_LIST_HEAD(&optee->notif.db);
>         optee->notif.bitmap = bitmap_zalloc(max_key, GFP_KERNEL);
> -       if (!optee->notif.bitmap)
> -               return -ENOMEM;
> -
> +       if (!optee->notif.bitmap) {
> +               rc = -ENOMEM;
> +               goto err_put_ctx;
> +       }
>         optee->notif.max_key = max_key;
>
> +       if (irq) {
> +               rc = request_threaded_irq(irq, notif_irq_handler,
> +                                         notif_irq_thread_fn,
> +                                         0, "optee_notification", optee);
> +               if (rc)
> +                       goto err_free_bitmap;
> +
> +               optee->notif.irq = irq;
> +       }
> +
>         return 0;
> +
> +err_free_bitmap:
> +       kfree(optee->notif.bitmap);
> +err_put_ctx:
> +       tee_dev_ctx_put(optee->notif.ctx);
> +       optee->notif.ctx = NULL;
> +
> +       return rc;
>  }
>
>  void optee_notif_uninit(struct optee *optee)
>  {
> +       if (optee->notif.ctx) {
> +               optee_stop_async_notif(optee->notif.ctx);
> +               if (optee->notif.irq) {
> +                       free_irq(optee->notif.irq, optee);
> +                       irq_dispose_mapping(optee->notif.irq);
> +               }
> +
> +               /*
> +                * The thread normally working with optee->notif.ctx was
> +                * stopped with free_irq() above.
> +                *
> +                * Note we're not using teedev_close_context() or
> +                * tee_client_close_context() since we have already called
> +                * tee_device_put() while initializing to avoid a circular
> +                * reference counting.
> +                */
> +               tee_dev_ctx_put(optee->notif.ctx);
> +       }
> +
>         kfree(optee->notif.bitmap);
>  }
> diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> index 81ff593ac4ec..35970932de34 100644
> --- a/drivers/tee/optee/optee_msg.h
> +++ b/drivers/tee/optee/optee_msg.h
> @@ -291,6 +291,13 @@ struct optee_msg_arg {
>   * [in] param[0].u.rmem.shm_ref                holds shared memory reference
>   * [in] param[0].u.rmem.offs           0
>   * [in] param[0].u.rmem.size           0
> + *
> + * OPTEE_MSG_CMD_DO_BOTTOM_HALF does the scheduled bottom half processing
> + * of a driver.
> + *
> + * OPTEE_MSG_CMD_STOP_ASYNC_NOTIF informs secure world that from now is
> + * normal world unable to process asynchronous notifications. Typically
> + * used when the driver is shut down.
>   */
>  #define OPTEE_MSG_CMD_OPEN_SESSION     0
>  #define OPTEE_MSG_CMD_INVOKE_COMMAND   1
> @@ -298,6 +305,8 @@ struct optee_msg_arg {
>  #define OPTEE_MSG_CMD_CANCEL           3
>  #define OPTEE_MSG_CMD_REGISTER_SHM     4
>  #define OPTEE_MSG_CMD_UNREGISTER_SHM   5
> +#define OPTEE_MSG_CMD_DO_BOTTOM_HALF   6
> +#define OPTEE_MSG_CMD_STOP_ASYNC_NOTIF 7
>  #define OPTEE_MSG_FUNCID_CALL_WITH_ARG 0x0004
>
>  #endif /* _OPTEE_MSG_H */
> diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
> index 7dc058d008b2..62365912a70b 100644
> --- a/drivers/tee/optee/optee_private.h
> +++ b/drivers/tee/optee/optee_private.h
> @@ -37,6 +37,8 @@ struct optee_call_queue {
>
>  struct optee_notif {
>         u_int max_key;
> +       unsigned int irq;
> +       struct tee_context *ctx;
>         /* Serializes access to the elements below in this struct */
>         spinlock_t lock;
>         struct list_head db;
> @@ -132,7 +134,7 @@ void optee_handle_rpc(struct tee_context *ctx, struct optee_rpc_param *param,
>                       struct optee_call_ctx *call_ctx);
>  void optee_rpc_finalize_call(struct optee_call_ctx *call_ctx);
>
> -int optee_notif_init(struct optee *optee, u_int max_key);
> +int optee_notif_init(struct optee *optee, u_int max_key, u_int irq);
>  void optee_notif_uninit(struct optee *optee);
>  int optee_notif_wait(struct optee *optee, u_int key);
>  int optee_notif_send(struct optee *optee, u_int key);
> @@ -159,6 +161,8 @@ int optee_close_session(struct tee_context *ctx, u32 session);
>  int optee_invoke_func(struct tee_context *ctx, struct tee_ioctl_invoke_arg *arg,
>                       struct tee_param *param);
>  int optee_cancel_req(struct tee_context *ctx, u32 cancel_id, u32 session);
> +int optee_do_bottom_half(struct tee_context *ctx);
> +int optee_stop_async_notif(struct tee_context *ctx);
>
>  void optee_enable_shm_cache(struct optee *optee);
>  void optee_disable_shm_cache(struct optee *optee);
> diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> index 80eb763a8a80..dcc275a1d66e 100644
> --- a/drivers/tee/optee/optee_smc.h
> +++ b/drivers/tee/optee/optee_smc.h
> @@ -107,6 +107,12 @@ struct optee_smc_call_get_os_revision_result {
>  /*
>   * Call with struct optee_msg_arg as argument
>   *
> + * When calling this function normal world has a few responsibilities:
> + * 1. It must be able to handle eventual RPCs
> + * 2. Non-secure interrupts should not be masked
> + * 3. If asynchronous notifications has be negotiated successfully, then
> + *    asynchronous notifications should be unmasked during this call.
> + *
>   * Call register usage:
>   * a0  SMC Function ID, OPTEE_SMC*CALL_WITH_ARG
>   * a1  Upper 32 bits of a 64-bit physical pointer to a struct optee_msg_arg
> @@ -195,7 +201,10 @@ struct optee_smc_get_shm_config_result {
>   * Normal return register usage:
>   * a0  OPTEE_SMC_RETURN_OK
>   * a1  bitfield of secure world capabilities OPTEE_SMC_SEC_CAP_*
> - * a2-7        Preserved
> + * a2  Bit[15:0]  Asynchronous notification interrupt ID, if supported
> + *     Bit[31:16] MBZ
> + * a3  The maximum secure world notification number
> + * a4-7        Preserved
>   *
>   * Error return register usage:
>   * a0  OPTEE_SMC_RETURN_ENOTAVAIL, can't use the capabilities from normal world
> @@ -218,6 +227,8 @@ struct optee_smc_get_shm_config_result {
>  #define OPTEE_SMC_SEC_CAP_VIRTUALIZATION       BIT(3)
>  /* Secure world supports Shared Memory with a NULL reference */
>  #define OPTEE_SMC_SEC_CAP_MEMREF_NULL          BIT(4)
> +/* Secure world supports asynchronous notification of normal world */
> +#define OPTEE_SMC_SEC_CAP_ASYNC_NOTIF          BIT(5)
>
>  #define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES 9
>  #define OPTEE_SMC_EXCHANGE_CAPABILITIES \
> @@ -226,8 +237,8 @@ struct optee_smc_get_shm_config_result {
>  struct optee_smc_exchange_capabilities_result {
>         unsigned long status;
>         unsigned long capabilities;
> -       unsigned long reserved0;
> -       unsigned long reserved1;
> +       unsigned long data0;
> +       unsigned long max_notif_value;
>  };
>
>  /*
> @@ -319,6 +330,68 @@ struct optee_smc_disable_shm_cache_result {
>  #define OPTEE_SMC_GET_THREAD_COUNT \
>         OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_THREAD_COUNT)
>
> +/*
> + * Inform OP-TEE that normal world is able to receive asynchronous
> + * notifications.
> + *
> + * Call requests usage:
> + * a0  SMC Function ID, OPTEE_SMC_ENABLE_ASYNC_NOTIF
> + * a1-6        Not used
> + * a7  Hypervisor Client ID register
> + *
> + * Normal return register usage:
> + * a0  OPTEE_SMC_RETURN_OK
> + * a1-7        Preserved
> + *
> + * Not supported return register usage:
> + * a0  OPTEE_SMC_RETURN_ENOTAVAIL
> + * a1-7        Preserved
> + */
> +#define OPTEE_SMC_FUNCID_ENABLE_ASYNC_NOTIF    16
> +#define OPTEE_SMC_ENABLE_ASYNC_NOTIF \
> +       OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_ENABLE_ASYNC_NOTIF)
> +
> +/*
> + * Retrieve a value of notifications pended since the last call of this
> + * function.
> + *
> + * OP-TEE keeps a records of all posted values. When an interrupts is
> + * received which indicates that there are posed values this function
> + * should be called until all pended values has been retrieved. When a
> + * value is retrieved it's cleared from the record in secure world.
> + *
> + * Call requests usage:
> + * a0  SMC Function ID, OPTEE_SMC_GET_ASYNC_NOTIF_VALUE
> + * a1-6        Not used
> + * a7  Hypervisor Client ID register
> + *
> + * Normal return register usage:
> + * a0  OPTEE_SMC_RETURN_OK
> + * a1  value
> + * a2  Bit[0]: OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID if the value in a1 is
> + *             valid, else 0 if no values where pending
> + * a2  Bit[1]: OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING if another value is
> + *             pending, else 0.
> + *     Bit[31:2]: MBZ
> + * a3-7        Preserved
> + *
> + * Not supported return register usage:
> + * a0  OPTEE_SMC_RETURN_ENOTAVAIL
> + * a1-7        Preserved
> + */
> +#define OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID      BIT(0)
> +#define OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING    BIT(1)
> +
> +/*
> + * Notification that OP-TEE expects a yielding call to do some bottom half
> + * work in a driver.
> + */
> +#define OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF     0
> +
> +#define OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE 17
> +#define OPTEE_SMC_GET_ASYNC_NOTIF_VALUE \
> +       OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE)
> +
>  /*
>   * Resume from RPC (for example after processing a foreign interrupt)
>   *
> --
> 2.31.1
>
>
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