From 69e097d467afaf2346149f55bbfb16849462fbc5 Mon Sep 17 00:00:00 2001 From: Jianping Li Date: Mon, 17 Aug 2026 16:13:30 +0800 Subject: [PATCH] UPSTREAM: misc: fastrpc: Drop unhandled DSP PD exit notification Newer DSP firmware implements a PD (Protection Domain) notification framework that sends PD state notifications upon request. The PD exit notification is unconditionally sent by the DSP with a fixed sentinel 0xABCDABCD in the context field. fastrpc_rpmsg_callback() treats every inbound message as an invoke response, so the sentinel is masked and shifted like any real response ((0xABCDABCD & 0xFF0) >> 4 == 188) and looked up in the channel's context idr. This is not merely cosmetic. In the common case idr slot 188 is empty, the lookup fails, and the driver only logs a spurious "No context ID matches response" error on every teardown. But the context idr is shared by every protection domain and the listener thread on the channel and is filled cyclically over [1, FASTRPC_CTX_MAX]. If slot 188 holds a live context when the sentinel arrives, the sentinel's return value is written into that unrelated in-flight invocation and it is completed early. Since neither the fastrpc library nor the driver supports the DSP PD notification framework, it is safe to drop the PD exit notification before it is ever turned into a context lookup. This removes both the log spam and the mis-completion race. A genuine response can never be masked: a real context is (idr_index << 4) | pd (at most 0xFF3) and can never equal the sentinel. Assisted-by: Claude:claude-opus-4-8 Reviewed-by: Ekansh Gupta Signed-off-by: Shawn Guo Signed-off-by: Srinivas Kandagatla Link: https://patch.msgid.link/20260729094352.111065-11-srini@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Jianping Li --- drivers/misc/fastrpc.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 2150bf00f518e..3df6c21a90276 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -48,6 +48,17 @@ */ #define FASTRPC_MAX_STATIC_HANDLE (20) #define FASTRPC_CTXID_MASK GENMASK(15, 8) + +/* + * Newer DSP firmware implements a PD (Protection Domain) notification + * framework that sends PD state notifications upon request. The PD exit + * notification is unconditionally sent by the DSP with this fixed sentinel + * in the context field rather than the context of an outstanding invocation. + * Since the fastrpc driver does not support the DSP PD notification framework, + * this message must be dropped rather than matched against the context idr. + */ +#define FASTRPC_DSP_PD_NOTIFY_CTX 0xABCDABCD + #define INIT_FILELEN_MAX (2 * 1024 * 1024) #define INIT_FILE_NAMELEN_MAX (128) #define FASTRPC_DEVICE_NAME "fastrpc" @@ -2830,6 +2841,14 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data, if (!cctx) return -ENODEV; + /* + * A PD exit notification from the DSP PD notification framework carries + * this sentinel rather than a real context. Drop it: a real context is + * (idr_index << 4) | pd and can never collide with this value. + */ + if (rsp->ctx == FASTRPC_DSP_PD_NOTIFY_CTX) + return 0; + ctxid = FIELD_GET(FASTRPC_CTXID_MASK, rsp->ctx); spin_lock_irqsave(&cctx->lock, flags);