On Thu, Nov 13, 2025 at 12:11:11PM +0530, Ekansh Gupta wrote: > For any remote call to DSP, after sending an invocation message, > fastRPC driver waits for glink response and during this time the > CPU can go into low power modes. This adds latency to overall fastrpc > call as CPU wakeup and scheduling latencies are included. Add polling > mode support with which fastRPC driver will poll continuously on a > memory after sending a message to remote subsystem which will eliminate > CPU wakeup and scheduling latencies and reduce fastRPC overhead. Poll > mode can be enabled by user by making a remote_handle64_control request.
Which request?? I thought it's enabled by making an IOCTL. > > Signed-off-by: Ekansh Gupta <[email protected]> > --- > drivers/misc/fastrpc.c | 138 ++++++++++++++++++++++++++++++++++-- > include/uapi/misc/fastrpc.h | 9 +++ > 2 files changed, 140 insertions(+), 7 deletions(-) > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c > index ccba3b6dfdfa..60de9dcb9815 100644 > --- a/drivers/misc/fastrpc.c > +++ b/drivers/misc/fastrpc.c > @@ -22,6 +22,8 @@ > #include <linux/firmware/qcom/qcom_scm.h> > #include <uapi/misc/fastrpc.h> > #include <linux/of_reserved_mem.h> > +#include <linux/compiler.h> > +#include <linux/iopoll.h> > > #define ADSP_DOMAIN_ID (0) > #define MDSP_DOMAIN_ID (1) > @@ -37,6 +39,7 @@ > #define FASTRPC_CTX_MAX (256) > #define FASTRPC_INIT_HANDLE 1 > #define FASTRPC_DSP_UTILITIES_HANDLE 2 > +#define FASTRPC_MAX_STATIC_HANDLE (20) > #define FASTRPC_CTXID_MASK (0xFF00) > #define FASTRPC_CTXID_POS (8) > #define INIT_FILELEN_MAX (2 * 1024 * 1024) > @@ -106,6 +109,12 @@ > > #define miscdev_to_fdevice(d) container_of(d, struct fastrpc_device, miscdev) > > +/* Poll response number from remote processor for call completion */ > +#define FASTRPC_POLL_RESPONSE (0xdecaf) > + > +/* Polling mode timeout limit */ > +#define FASTRPC_POLL_MAX_TIMEOUT_US (10000) > + > struct fastrpc_phy_page { > u64 addr; /* physical address */ > u64 size; /* size of contiguous region */ > @@ -236,8 +245,14 @@ struct fastrpc_invoke_ctx { > u32 sc; > u64 *fdlist; > u32 *crc; > + /* Poll memory that DSP updates */ > + u32 *poll; > u64 ctxid; > u64 msg_sz; > + /* work done status flag */ > + bool is_work_done; > + /* process updates poll memory instead of glink response */ > + bool is_polled; > struct kref refcount; > struct list_head node; /* list of ctxs */ > struct completion work; > @@ -301,6 +316,8 @@ struct fastrpc_user { > int client_id; > int pd; > bool is_secure_dev; > + /* Flags poll mode state */ > + bool poll_mode; > /* Lock for lists */ > spinlock_t lock; > /* lock for allocations */ > @@ -894,7 +911,8 @@ static int fastrpc_get_meta_size(struct > fastrpc_invoke_ctx *ctx) > sizeof(struct fastrpc_invoke_buf) + > sizeof(struct fastrpc_phy_page)) * ctx->nscalars + > sizeof(u64) * FASTRPC_MAX_FDLIST + > - sizeof(u32) * FASTRPC_MAX_CRCLIST; > + sizeof(u32) * FASTRPC_MAX_CRCLIST + > + sizeof(u32); > > return size; > } > @@ -990,6 +1008,7 @@ static int fastrpc_get_args(u32 kernel, struct > fastrpc_invoke_ctx *ctx) > list = fastrpc_invoke_buf_start(rpra, ctx->nscalars); > pages = fastrpc_phy_page_start(list, ctx->nscalars); > ctx->fdlist = (u64 *)(pages + ctx->nscalars); > + ctx->poll = (u32 *)(ctx->fdlist + FASTRPC_MAX_FDLIST + > FASTRPC_MAX_CRCLIST); > args = (uintptr_t)ctx->buf->virt + metalen; > rlen = pkt_size - metalen; > ctx->rpra = rpra; > @@ -1158,6 +1177,75 @@ static int fastrpc_invoke_send(struct > fastrpc_session_ctx *sctx, > > } > > +static inline u32 fastrpc_poll_op(void *p) > +{ > + struct fastrpc_invoke_ctx *ctx = p; > + > + dma_rmb(); > + return READ_ONCE(*ctx->poll); How does this work with caches? Does it require dma-coherent fastrpc devices? > +} > + > +static int poll_for_remote_response(struct fastrpc_invoke_ctx *ctx) > +{ > + u32 val; > + int ret; > + > + /* > + * Poll until DSP writes FASTRPC_POLL_RESPONSE into *ctx->poll > + * or until another path marks the work done. > + */ > + ret = read_poll_timeout_atomic(fastrpc_poll_op, val, > + (val == FASTRPC_POLL_RESPONSE) || > + ctx->is_work_done, 1, > + FASTRPC_POLL_MAX_TIMEOUT_US, false, ctx); > + > + if (!ret && val == FASTRPC_POLL_RESPONSE) { > + ctx->is_work_done = true; > + ctx->retval = 0; > + } > + > + if (ret == -ETIMEDOUT) > + ret = -EIO; > + > + return ret; > +} > + > +static inline int fastrpc_wait_for_response(struct fastrpc_invoke_ctx *ctx, > + u32 kernel) > +{ > + int err = 0; > + > + if (kernel) { > + if (!wait_for_completion_timeout(&ctx->work, 10 * HZ)) > + err = -ETIMEDOUT; > + } else { > + err = wait_for_completion_interruptible(&ctx->work); > + } > + > + return err; > +} > + > +static int fastrpc_wait_for_completion(struct fastrpc_invoke_ctx *ctx, > + u32 kernel) > +{ > + int err; > + > + do { > + if (ctx->is_polled) { > + err = poll_for_remote_response(ctx); > + /* If polling timed out, move to normal response mode */ > + if (err) > + ctx->is_polled = false; > + } else { > + err = fastrpc_wait_for_response(ctx, kernel); > + if (err) > + return err; > + } > + } while (!ctx->is_work_done); > + > + return err; > +} > + > static int fastrpc_internal_invoke(struct fastrpc_user *fl, u32 kernel, > u32 handle, u32 sc, > struct fastrpc_invoke_args *args) > @@ -1193,16 +1281,25 @@ static int fastrpc_internal_invoke(struct > fastrpc_user *fl, u32 kernel, > if (err) > goto bail; > > - if (kernel) { > - if (!wait_for_completion_timeout(&ctx->work, 10 * HZ)) > - err = -ETIMEDOUT; > - } else { > - err = wait_for_completion_interruptible(&ctx->work); > - } > + /* > + * Set message context as polled if the call is for a user PD > + * dynamic module and user has enabled poll mode. > + */ > + if (handle > FASTRPC_MAX_STATIC_HANDLE && fl->pd == USER_PD && > + fl->poll_mode) > + ctx->is_polled = true; > + > + err = fastrpc_wait_for_completion(ctx, kernel); > > if (err) > goto bail; > > + if (!ctx->is_work_done) { > + err = -ETIMEDOUT; > + dev_dbg(fl->sctx->dev, "Invalid workdone state for handle 0x%x, > sc 0x%x\n", > + handle, sc); > + goto bail; > + } > /* make sure that all memory writes by DSP are seen by CPU */ > dma_rmb(); > /* populate all the output buffers with results */ > @@ -1780,6 +1877,29 @@ static int fastrpc_get_info_from_kernel(struct > fastrpc_ioctl_capability *cap, > return 0; > } > > +static int fastrpc_set_option(struct fastrpc_user *fl, char __user *argp) > +{ > + struct fastrpc_ioctl_set_option opt = {0}; > + int i; > + > + if (copy_from_user(&opt, argp, sizeof(opt))) > + return -EFAULT; > + > + for (i = 0; i < ARRAY_SIZE(opt.reserved); i++) { > + if (opt.reserved[i] != 0) > + return -EINVAL; > + } Empty line. > + if (opt.req != FASTRPC_POLL_MODE) > + return -EINVAL; > + > + if (opt.enable) > + fl->poll_mode = true; > + else > + fl->poll_mode = false; > + > + return 0; > +} > + > static int fastrpc_get_dsp_info(struct fastrpc_user *fl, char __user *argp) > { > struct fastrpc_ioctl_capability cap = {0}; > @@ -2134,6 +2254,9 @@ static long fastrpc_device_ioctl(struct file *file, > unsigned int cmd, > case FASTRPC_IOCTL_MEM_UNMAP: > err = fastrpc_req_mem_unmap(fl, argp); > break; > + case FASTRPC_IOCTL_SET_OPTION: > + err = fastrpc_set_option(fl, argp); > + break; > case FASTRPC_IOCTL_GET_DSP_INFO: > err = fastrpc_get_dsp_info(fl, argp); > break; > @@ -2465,6 +2588,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device > *rpdev, void *data, > > ctx->retval = rsp->retval; > complete(&ctx->work); > + ctx->is_work_done = true; > > /* > * The DMA buffer associated with the context cannot be freed in > diff --git a/include/uapi/misc/fastrpc.h b/include/uapi/misc/fastrpc.h > index c6e2925f47e6..6c1375ba0042 100644 > --- a/include/uapi/misc/fastrpc.h > +++ b/include/uapi/misc/fastrpc.h > @@ -16,6 +16,7 @@ > #define FASTRPC_IOCTL_INIT_CREATE_STATIC _IOWR('R', 9, struct > fastrpc_init_create_static) > #define FASTRPC_IOCTL_MEM_MAP _IOWR('R', 10, struct > fastrpc_mem_map) > #define FASTRPC_IOCTL_MEM_UNMAP _IOWR('R', 11, struct > fastrpc_mem_unmap) > +#define FASTRPC_IOCTL_SET_OPTION _IOWR('R', 12, struct > fastrpc_ioctl_set_option) > #define FASTRPC_IOCTL_GET_DSP_INFO _IOWR('R', 13, struct > fastrpc_ioctl_capability) > > /** > @@ -66,6 +67,8 @@ enum fastrpc_proc_attr { > > /* Fastrpc attribute for memory protection of buffers */ > #define FASTRPC_ATTR_SECUREMAP (1) > +/* Set option request ID to enable poll mode */ > +#define FASTRPC_POLL_MODE (1) > > struct fastrpc_invoke_args { > __u64 ptr; > @@ -133,6 +136,12 @@ struct fastrpc_mem_unmap { > __s32 reserved[5]; > }; > > +struct fastrpc_ioctl_set_option { > + __u32 req; /* request id */ > + __u32 enable; /* enable flag */ s/enable/value/ ? > + __s32 reserved[6]; I think you got feedback from Greg regarding handling of reserved fields few months ago. Please drop them. > +}; > + > struct fastrpc_ioctl_capability { > __u32 unused; /* deprecated, ignored by the kernel */ > __u32 attribute_id; > -- > 2.34.1 > -- With best wishes Dmitry
