On 1/29/2025 4:59 AM, Dmitry Baryshkov wrote: > On Mon, Jan 27, 2025 at 10:12:38AM +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. Adding a 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. >> With this change, DSP always sends a glink response which will >> get ignored if polling mode didn't time out. > Is there a chance to implement actual async I/O protocol with the help > of the poll() call instead of hiding the polling / wait inside the > invoke2? This design is based on the implementation on DSP firmware as of today: Call flow: https://github.com/quic-ekangupt/fastrpc/blob/invokev2/Docs/invoke_v2.md#5-polling-mode Can you please give some reference to the async I/O protocol that you've suggested? I can check if it can be implemented here. --ekansh > >> Signed-off-by: Ekansh Gupta <quic_ekangupt@xxxxxxxxxxx> >> --- >> drivers/misc/fastrpc.c | 122 +++++++++++++++++++++++++++++++++--- >> include/uapi/misc/fastrpc.h | 3 +- >> 2 files changed, 114 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c >> index cfacee0dded5..257a741af115 100644 >> --- a/drivers/misc/fastrpc.c >> +++ b/drivers/misc/fastrpc.c >> @@ -19,6 +19,7 @@ >> #include <linux/rpmsg.h> >> #include <linux/scatterlist.h> >> #include <linux/slab.h> >> +#include <linux/delay.h> >> #include <linux/firmware/qcom/qcom_scm.h> >> #include <uapi/misc/fastrpc.h> >> #include <linux/of_reserved_mem.h> >> @@ -38,6 +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 (0xFF0) >> #define INIT_FILELEN_MAX (2 * 1024 * 1024) >> #define INIT_FILE_NAMELEN_MAX (128) >> @@ -106,6 +108,19 @@ >> >> #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) >> +/* timeout in us for polling until memory barrier */ >> +#define FASTRPC_POLL_TIME_MEM_UPDATE (500) >> + >> +/* Response types supported for RPC calls */ >> +enum fastrpc_response_flags { >> + /* normal job completion glink response */ >> + NORMAL_RESPONSE = 0, >> + /* process updates poll memory instead of glink response */ >> + POLL_MODE = 1, >> +}; >> + >> static const char *domains[FASTRPC_DEV_MAX] = { "adsp", "mdsp", >> "sdsp", "cdsp", "cdsp1" }; >> struct fastrpc_phy_page { >> @@ -238,9 +253,16 @@ struct fastrpc_invoke_ctx { >> u32 sc; >> u64 *fdlist; >> u32 *crclist; >> + u32 *poll; >> void __user *crc; >> u64 ctxid; >> u64 msg_sz; >> + /* Threads poll for specified timeout and fall back to glink wait */ >> + u64 poll_timeout; >> + /* work done status flag */ >> + bool is_work_done; >> + /* response flags from remote processor */ >> + enum fastrpc_response_flags rsp_flags; >> struct kref refcount; >> struct list_head node; /* list of ctxs */ >> struct completion work; >> @@ -258,6 +280,7 @@ struct fastrpc_invoke_ctx { >> struct fastrpc_ctx_args { >> struct fastrpc_invoke_args *args; >> void __user *crc; >> + u64 poll_timeout; >> }; >> >> struct fastrpc_session_ctx { >> @@ -619,11 +642,14 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc( >> fastrpc_channel_ctx_get(cctx); >> >> ctx->crc = cargs->crc; >> + ctx->poll_timeout = cargs->poll_timeout; >> ctx->sc = sc; >> ctx->retval = -1; >> ctx->pid = current->pid; >> ctx->client_id = user->client_id; >> ctx->cctx = cctx; >> + ctx->rsp_flags = NORMAL_RESPONSE; >> + ctx->is_work_done = false; >> init_completion(&ctx->work); >> INIT_WORK(&ctx->put_work, fastrpc_context_put_wq); >> >> @@ -882,7 +908,8 @@ 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; >> } >> @@ -975,6 +1002,8 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx) >> pages = fastrpc_phy_page_start(list, ctx->nscalars); >> ctx->fdlist = (u64 *)(pages + ctx->nscalars); >> ctx->crclist = (u32 *)(ctx->fdlist + FASTRPC_MAX_FDLIST); >> + ctx->poll = (u32 *)(ctx->crclist + FASTRPC_MAX_CRCLIST); >> + >> args = (uintptr_t)ctx->buf->virt + metalen; >> rlen = pkt_size - metalen; >> ctx->rpra = rpra; >> @@ -1145,6 +1174,72 @@ static int fastrpc_invoke_send(struct fastrpc_session_ctx *sctx, >> >> } >> >> +static int poll_for_remote_response(struct fastrpc_invoke_ctx *ctx, u64 timeout) >> +{ >> + int err = -EIO, i, j; >> + >> + /* poll on memory for DSP response. Return failure on timeout */ >> + for (i = 0, j = 0; i < timeout; i++, j++) { >> + if (*ctx->poll == FASTRPC_POLL_RESPONSE) { >> + err = 0; >> + ctx->is_work_done = true; >> + ctx->retval = 0; >> + break; >> + } >> + if (j == FASTRPC_POLL_TIME_MEM_UPDATE) { >> + /* make sure that all poll memory writes by DSP are seen by CPU */ >> + dma_rmb(); >> + j = 0; >> + } >> + udelay(1); >> + } >> + return err; >> +} >> + >> +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 { >> + switch (ctx->rsp_flags) { >> + case NORMAL_RESPONSE: >> + err = fastrpc_wait_for_response(ctx, kernel); >> + if (err || ctx->is_work_done) >> + return err; >> + break; >> + case POLL_MODE: >> + err = poll_for_remote_response(ctx, ctx->poll_timeout); >> + /* If polling timed out, move to normal response mode */ >> + if (err) >> + ctx->rsp_flags = NORMAL_RESPONSE; >> + break; >> + default: >> + err = -EBADR; >> + dev_dbg(ctx->fl->sctx->dev, >> + "unsupported response type:0x%x\n", ctx->rsp_flags); >> + break; >> + } >> + } while (!ctx->is_work_done); >> + >> + return err; >> +} >> + >> static int fastrpc_internal_invoke(struct fastrpc_user *fl, u32 kernel, >> u32 handle, u32 sc, >> struct fastrpc_ctx_args *cargs) >> @@ -1180,16 +1275,20 @@ 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); >> - } >> + if (ctx->poll_timeout != 0 && handle > FASTRPC_MAX_STATIC_HANDLE >> + && fl->pd == USER_PD) >> + ctx->rsp_flags = POLL_MODE; >> >> + 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 */ >> @@ -1769,7 +1868,7 @@ static int fastrpc_invokev2(struct fastrpc_user *fl, char __user *argp) >> return -EFAULT; >> >> /* Check if all reserved fields are zero */ >> - for (i = 0; i < 16; i++) { >> + for (i = 0; i < 14; i++) { >> if (inv2.reserved[i] != 0) >> return -EINVAL; >> } >> @@ -1779,6 +1878,7 @@ static int fastrpc_invokev2(struct fastrpc_user *fl, char __user *argp) >> return -ENOMEM; >> >> cargs->crc = (void __user *)(uintptr_t)inv2.crc; >> + cargs->poll_timeout = inv2.poll_timeout; >> >> err = fastrpc_remote_invoke(fl, &inv2.inv, cargs); >> kfree(cargs); >> @@ -2581,12 +2681,14 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data, >> ctx = idr_find(&cctx->ctx_idr, ctxid); >> spin_unlock_irqrestore(&cctx->lock, flags); >> >> + /* Ignore this failure as context returned will be NULL for polling mode */ >> if (!ctx) { >> - dev_err(&rpdev->dev, "No context ID matches response\n"); >> - return -ENOENT; >> + dev_dbg(&rpdev->dev, "No context ID matches response\n"); >> + return 0; >> } >> >> ctx->retval = rsp->retval; >> + ctx->is_work_done = true; >> complete(&ctx->work); >> >> /* >> diff --git a/include/uapi/misc/fastrpc.h b/include/uapi/misc/fastrpc.h >> index 406b80555d41..1920c537bbbf 100644 >> --- a/include/uapi/misc/fastrpc.h >> +++ b/include/uapi/misc/fastrpc.h >> @@ -84,7 +84,8 @@ struct fastrpc_invoke { >> struct fastrpc_invoke_v2 { >> struct fastrpc_invoke inv; >> __u64 crc; >> - __u32 reserved[16]; >> + __u64 poll_timeout; >> + __u32 reserved[14]; >> }; >> >> struct fastrpc_init_create { >> -- >> 2.34.1 >>
