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Wed, 01 Apr 2026 22:49:46 -0700 (PDT) Received: from hu-ekangupt-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82cf9b5fb22sm2167747b3a.26.2026.04.01.22.49.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 22:49:46 -0700 (PDT) From: Ekansh Gupta To: srini@kernel.org, linux-arm-msm@vger.kernel.org Cc: gregkh@linuxfoundation.org, quic_bkumar@quicinc.com, linux-kernel@vger.kernel.org, quic_chennak@quicinc.com, dri-devel@lists.freedesktop.org, arnd@arndb.de, dmitry.baryshkov@oss.qualcomm.com, andersson@kernel.org, konrad.dybcio@oss.qualcomm.com Subject: [PATCH v7 4/4] misc: fastrpc: Add polling mode support for fastRPC driver Date: Thu, 2 Apr 2026 11:19:23 +0530 Message-Id: <20260402054923.3061925-5-ekansh.gupta@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260402054923.3061925-1-ekansh.gupta@oss.qualcomm.com> References: <20260402054923.3061925-1-ekansh.gupta@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Authority-Analysis: v=2.4 cv=TqLrRTXh c=1 sm=1 tr=0 ts=69ce037c cx=c_pps a=rEQLjTOiSrHUhVqRoksmgQ==:117 a=ZePRamnt/+rB5gQjfz0u9A==:17 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=YMgV9FUhrdKAYTUUvYB2:22 a=EUspDBNiAAAA:8 a=TEHdEMHTk_fMHrPBF0kA:9 a=2VI0MkxyNR6bbpdq8BZq:22 X-Proofpoint-ORIG-GUID: ntCSw_S0KuWRc4J0gg54CKmhh67kn3FQ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDAyMDA0OCBTYWx0ZWRfX00SdMNt8yiPd DuiELAi5yDmd6a3h/LPcCY9Eeisd4FWqd+Jxw/tTIpbonpnEf9TOTzlZVALnNq1cSd568wJH4pS 5CpQwekfgJvAuoYaUEE7QVdMg+H0WpaDrQLVCW+MOSmZ8DvvIkz7nFWLkvicGrAkrbkFJLxfAqh cIMbPvjXH4UuYCKrCpMD2olAtqzi2p/SGc5kFDs+pL36r3GngUb4W98GmAyZqaBo37KHjvWlKkz UWF6bNYJP6AzZsLjOzAwJAggoWMM2A59x6eNDnY7fhzpbpsxhBGrwUGDQW8Elco9GafiNH5s8x0 jNPgEeatYiUzkBwe0XpA/5LDvxtHShvqXe9oCOf2gXbthElad5zFcDUO8aH5krHi2a2VEXt0XMj R38oMbUiMHsYJ72acpXUzr+XacBrs/5pShY1/Fh8r5t0zvUYPfLTQoeJL8wECood5L6MmT8B8FH OtCYQvcfdVjya7nxXGQ== X-Proofpoint-GUID: ntCSw_S0KuWRc4J0gg54CKmhh67kn3FQ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-02_01,2026-04-01_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2604020048 Content-Type: text/plain; charset="utf-8" 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. In case poll timeout happens, the call will fallback to normal RPC mode. Poll mode can be enabled by user by using FASTRPC_IOCTL_SET_OPTION ioctl request with FASTRPC_POLL_MODE request id. Signed-off-by: Ekansh Gupta --- drivers/misc/fastrpc.c | 132 ++++++++++++++++++++++++++++++++++-- include/uapi/misc/fastrpc.h | 10 +++ 2 files changed, 135 insertions(+), 7 deletions(-) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 4363e0cc296b..25f385f4704d 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -24,6 +24,8 @@ #include #include #include +#include +#include =20 #define ADSP_DOMAIN_ID (0) #define MDSP_DOMAIN_ID (1) @@ -38,6 +40,7 @@ #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 GENMASK(15, 8) #define INIT_FILELEN_MAX (2 * 1024 * 1024) #define INIT_FILE_NAMELEN_MAX (128) @@ -106,6 +109,12 @@ =20 #define miscdev_to_fdevice(d) container_of(d, struct fastrpc_device, miscd= ev) =20 +/* 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 { dma_addr_t addr; /* dma 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; @@ -308,6 +323,8 @@ 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 */ @@ -923,7 +940,8 @@ 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); =20 return size; } @@ -1019,6 +1037,9 @@ static int fastrpc_get_args(u32 kernel, struct fastrp= c_invoke_ctx *ctx) list =3D fastrpc_invoke_buf_start(rpra, ctx->nscalars); pages =3D fastrpc_phy_page_start(list, ctx->nscalars); ctx->fdlist =3D (u64 *)(pages + ctx->nscalars); + ctx->poll =3D (u32 *)((uintptr_t)ctx->fdlist + sizeof(u64) * FASTRPC_MAX_= FDLIST + + sizeof(u32) * FASTRPC_MAX_CRCLIST); + args =3D (uintptr_t)ctx->buf->virt + metalen; rlen =3D pkt_size - metalen; ctx->rpra =3D rpra; @@ -1188,6 +1209,74 @@ static int fastrpc_invoke_send(struct fastrpc_sessio= n_ctx *sctx, =20 } =20 +static inline u32 fastrpc_poll_op(void *p) +{ + struct fastrpc_invoke_ctx *ctx =3D p; + + dma_rmb(); + return READ_ONCE(*ctx->poll); +} + +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 =3D read_poll_timeout_atomic(fastrpc_poll_op, val, + (val =3D=3D FASTRPC_POLL_RESPONSE) || ctx->is_work_done, 1, + FASTRPC_POLL_MAX_TIMEOUT_US, false, ctx); + + if (!ret && val =3D=3D FASTRPC_POLL_RESPONSE) { + ctx->is_work_done =3D true; + ctx->retval =3D 0; + } + + if (ret =3D=3D -ETIMEDOUT) + ret =3D -EIO; + + return ret; +} + +static inline int fastrpc_wait_for_response(struct fastrpc_invoke_ctx *ctx, + u32 kernel) +{ + int err =3D 0; + + if (kernel) { + if (!wait_for_completion_timeout(&ctx->work, 10 * HZ)) + err =3D -ETIMEDOUT; + } else { + err =3D 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 =3D poll_for_remote_response(ctx); + /* If polling timed out, move to normal response mode */ + if (err) + ctx->is_polled =3D false; + } else { + err =3D fastrpc_wait_for_response(ctx, kernel); + if (err) + return err; + } + } while (!ctx->is_work_done); + + return 0; +} + static int fastrpc_internal_invoke(struct fastrpc_user *fl, u32 kernel, u32 handle, u32 sc, struct fastrpc_invoke_args *args) @@ -1223,13 +1312,14 @@ static int fastrpc_internal_invoke(struct fastrpc_u= ser *fl, u32 kernel, if (err) goto bail; =20 - if (kernel) { - if (!wait_for_completion_timeout(&ctx->work, 10 * HZ)) - err =3D -ETIMEDOUT; - } else { - err =3D 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 =3D=3D USER_PD && fl->po= ll_mode) + ctx->is_polled =3D true; =20 + err =3D fastrpc_wait_for_completion(ctx, kernel); if (err) goto bail; =20 @@ -1812,6 +1902,30 @@ static int fastrpc_get_info_from_kernel(struct fastr= pc_ioctl_capability *cap, return 0; } =20 +static int fastrpc_set_option(struct fastrpc_user *fl, char __user *argp) +{ + struct fastrpc_ioctl_set_option opt =3D {0}; + int i; + + if (copy_from_user(&opt, argp, sizeof(opt))) + return -EFAULT; + + for (i =3D 0; i < ARRAY_SIZE(opt.reserved); i++) { + if (opt.reserved[i] !=3D 0) + return -EINVAL; + } + + if (opt.req !=3D FASTRPC_POLL_MODE) + return -EINVAL; + + if (opt.value) + fl->poll_mode =3D true; + else + fl->poll_mode =3D false; + + return 0; +} + static int fastrpc_get_dsp_info(struct fastrpc_user *fl, char __user *argp) { struct fastrpc_ioctl_capability cap =3D {0}; @@ -2167,6 +2281,9 @@ static long fastrpc_device_ioctl(struct file *file, u= nsigned int cmd, case FASTRPC_IOCTL_MEM_UNMAP: err =3D fastrpc_req_mem_unmap(fl, argp); break; + case FASTRPC_IOCTL_SET_OPTION: + err =3D fastrpc_set_option(fl, argp); + break; case FASTRPC_IOCTL_GET_DSP_INFO: err =3D fastrpc_get_dsp_info(fl, argp); break; @@ -2518,6 +2635,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device= *rpdev, void *data, } =20 ctx->retval =3D rsp->retval; + ctx->is_work_done =3D true; complete(&ctx->work); =20 /* diff --git a/include/uapi/misc/fastrpc.h b/include/uapi/misc/fastrpc.h index c6e2925f47e6..c37e24a764ae 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_o= ption) #define FASTRPC_IOCTL_GET_DSP_INFO _IOWR('R', 13, struct fastrpc_ioctl_cap= ability) =20 /** @@ -67,6 +68,9 @@ enum fastrpc_proc_attr { /* Fastrpc attribute for memory protection of buffers */ #define FASTRPC_ATTR_SECUREMAP (1) =20 +/* Set option request ID to enable poll mode */ +#define FASTRPC_POLL_MODE (1) + struct fastrpc_invoke_args { __u64 ptr; __u64 length; @@ -133,6 +137,12 @@ struct fastrpc_mem_unmap { __s32 reserved[5]; }; =20 +struct fastrpc_ioctl_set_option { + __u32 req; /* request id */ + __u32 value; /* value */ + __s32 reserved[6]; +}; + struct fastrpc_ioctl_capability { __u32 unused; /* deprecated, ignored by the kernel */ __u32 attribute_id; --=20 2.34.1