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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b083655b5dsm20723185ad.52.2026.03.20.01.44.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Mar 2026 01:45:01 -0700 (PDT) Message-ID: <519ca61b-049e-4e2f-a9fc-9b4621574470@oss.qualcomm.com> Date: Fri, 20 Mar 2026 16:44:54 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] coresight: platform: check the availability of the endpoint before parse To: Leo Yan Cc: Suzuki K Poulose , Mike Leach , James Clark , Alexander Shishkin , Tingwei Zhang , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260320-add-availability-check-v1-1-b2e39cdeb6e0@oss.qualcomm.com> <20260320082549.GO8048@e132581.arm.com> Content-Language: en-US From: Jie Gan In-Reply-To: <20260320082549.GO8048@e132581.arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: XrXPQAC09IJkncp_bpF3TDH7KFN6Up8G X-Authority-Analysis: v=2.4 cv=Rv/I7SmK c=1 sm=1 tr=0 ts=69bd0910 cx=c_pps a=IZJwPbhc+fLeJZngyXXI0A==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=EUspDBNiAAAA:8 a=XMd_ep3at93-ufPvPDIA:9 a=QEXdDO2ut3YA:10 a=uG9DUKGECoFWVXl0Dc02:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzIwMDA2NSBTYWx0ZWRfX5gmtjQbd+9RP Od7XwOeeYO6xNZEEKZpUtiH0IvzpzczIluFa/iut+uqG/5FyIOfE8oTx5FDvfQBfh4tWsvKiInJ TjZs19sqkv2SkbNEVvwSLk51uctF/Kz4mzfIH7jYdBARHHw5pnNGFtg3b/J5F4iyNeg1O3QTw50 Hu7EmCDqEh3fBHq9eYl81rwBh5JIXrOqUTbWgNlHhEdZTjLAXhphgvDLfG2itdZnOf/e5jmWxeW pINsElAZA3pjl46i3rzPY/VSARkn753jm8oljOIQ82rUh9h9/5ETOzRaAS2lFA0APgohD/McJGs PMvZc8KwgEvW8nrGzA4JLhdX4x1oAuW1OAELJqQmI3IdPe/uzH4dUd1fHsRcPeNQj2i0S/oQqyk BwLmvk3yXYx6/Ev/9J07xPRbQhtKtgSWcDw85+x0kaq7qdAG+JWMMAnSsXVB60JfEvf5VvpJC1f z3iy0ytk+szVQHfhJew== X-Proofpoint-ORIG-GUID: XrXPQAC09IJkncp_bpF3TDH7KFN6Up8G 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=2026-03-20_01,2026-03-19_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 spamscore=0 phishscore=0 bulkscore=0 impostorscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603200065 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260320_014504_759716_7D37334D X-CRM114-Status: GOOD ( 23.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Leo, On 3/20/2026 4:25 PM, Leo Yan wrote: > On Fri, Mar 20, 2026 at 03:31:12PM +0800, Jie Gan wrote: >> Check endpoint availability before parsing it. If parsing a connected >> endpoint fails, the probe is deferred until the endpoint becomes >> available, or eventually fails. > > I want to clarify a bit the failure flow. > > Does this mean coresight_find_device_by_fwnode() returns NULL when the > remote device is not found, resulting in -EPROBE_DEFER, but the probe > never waits for the remote device to become available? It's about the coresight_find_device_by_fwnode() returns NULL, resulting in -EPROBE_DEFER. So the probe process will re-start after several seconds, but always failed because we have a "disabled" device node in DT(we can see this device in DT, but it never becomes available). It's ok if the device only has one remote device, but has issue with more than one remote devices. Consider below situation: device0 | | device1 device2(status = "disabled") The probe of device0 succeeds only when device1 and device2 are available at probe time. But I think it's ok to probe the device0 only with device1 available. Thanks, Jie > >> In some legacy cases, a replicator >> has two output ports where one is disabled and the other is available. >> The replicator probe always fails because the disabled endpoint never >> becomes available for parsing. In addition, there is no need to defer >> probing a device that is connected to a disabled device, which improves >> probe performance. >> >> Signed-off-by: Jie Gan >> --- >> drivers/hwtracing/coresight/coresight-platform.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c >> index 0ca3bd762454..e337b6e2bf32 100644 >> --- a/drivers/hwtracing/coresight/coresight-platform.c >> +++ b/drivers/hwtracing/coresight/coresight-platform.c >> @@ -220,6 +220,8 @@ static int of_coresight_parse_endpoint(struct device *dev, >> rparent = of_coresight_get_port_parent(rep); >> if (!rparent) >> break; >> + if (!of_device_is_available(rparent)) >> + break; >> if (of_graph_parse_endpoint(rep, &rendpoint)) >> break; >> >> >> --- >> base-commit: b5d083a3ed1e2798396d5e491432e887da8d4a06 >> change-id: 20260320-add-availability-check-4cb2ee6e520b >> >> Best regards, >> -- >> Jie Gan >>