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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a3eee8cf46sm790568e87.23.2026.04.10.07.43.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Apr 2026 07:43:56 -0700 (PDT) Message-ID: Date: Fri, 10 Apr 2026 16:43:54 +0200 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] thunderbolt: debugfs: Don't stop reading SB registers if just one fails To: Mika Westerberg Cc: Konrad Dybcio , Andreas Noever , Mika Westerberg , Yehezkel Bernat , usb4-upstream@oss.qualcomm.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260409-topic-tbt_sb_debugfs-v1-1-131540e0cc2b@oss.qualcomm.com> <20260409120457.GH3552@black.igk.intel.com> <75c962d1-7ade-483b-bbc9-a6c6140fc0e9@oss.qualcomm.com> <20260409143203.GI3552@black.igk.intel.com> <7d65539f-ece6-4e7c-a13e-6b12920346fa@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <7d65539f-ece6-4e7c-a13e-6b12920346fa@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDEwMDEzOCBTYWx0ZWRfX/kpq29RscUuj w8rN0ElWieny+qb18scOZt53A2L8b/v7EFGNKJcg69yOM44aEZ3sEjnczdUFBxQHCDJHKXMwy+X nAD3G5fgT9cb4u4CCw1aV3DUQJ/mMTKVGnTcrRuA4oOliJyeSNRiK62blKpVU1Oh8HI3s04Kp3P /NunqUdQ/qNPPcuVQdcc89Skp9GnZiQJ44HuX9QQuY57id6iV0vgcQjcdIaoYm6u/LWNXUtdvc4 q3J99KL3vh30utlwhKyCaFo20wp2IEGCxxk/51F2yBzE2K0sFzpPCSEtOZuSDzg6s2lV0ZcYYt9 1Onqd7rS0E/9IMz+AWMxmdZZOEEG+hV1e4AWGrEW3kYezWTcVGbokHhTruETE0u6MEbu12t7Q+z oIU6z4GM+uyoXXZxPuGzP0YEJlqSpvlfk3c1XIKyUt00c2KmoPviPPFL24wNRYzmChGXgxyQqWQ ZT7T2NIs+Y6oNqKhq3Q== X-Proofpoint-GUID: 8s2z06EUPEyz68hF4wZVju-m_OVl809k X-Proofpoint-ORIG-GUID: 8s2z06EUPEyz68hF4wZVju-m_OVl809k X-Authority-Analysis: v=2.4 cv=O7YJeh9W c=1 sm=1 tr=0 ts=69d90cae cx=c_pps a=mPf7EqFMSY9/WdsSgAYMbA==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=_aRDFbF4L5SVI7mo-8QA:9 a=QEXdDO2ut3YA:10 a=dawVfQjAaf238kedN5IG:22 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=2026-04-10_04,2026-04-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 phishscore=0 priorityscore=1501 adultscore=0 impostorscore=0 malwarescore=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604100138 On 4/10/26 4:29 PM, Konrad Dybcio wrote: > On 4/9/26 4:32 PM, Mika Westerberg wrote: >> On Thu, Apr 09, 2026 at 02:59:22PM +0200, Konrad Dybcio wrote: >>> On 4/9/26 2:04 PM, Mika Westerberg wrote: > > [...] > >>>> I assume you have tested this on a hardware that supports this too, right? >>> >>> Hardware that exposes that register this does not exercise the altered >>> code path. >> >> Well it may happen now that previously we got -EIO from some other register >> and we stopped there, now this changes and we actually continue reading so >> this definitely should be tested. > > The only register before USB4_SB_GEN4_TXFFE that isn't in-spec for > both retimers in v1.0 and v2.0 is USB4_SB_LRD_TUNING (0x07). The PS8830 > interestingly reports all zeroes (not a bounce). > > The registers following USB4_SB_GEN4_TXFFE in the array are > USB4_SB_VERSION and USB4_SB_DATA. The former is not accessed anywhere > else in the code, at first glance. The latter is, during NVM r/w and > in margining ops, which have definitely been in use for a long time. > > Plus both of them are the v1.0 spec. The USB4_SB_GEN4_TXFFE specifically > isn't (the retimer supplement pdf lists it as Rsvd, the main spec pdf > omits it in the SB register table), as it wasn't previously useful (since > Gen4 came about in v2.0). > > > I don't think there's an easy way to limit the reading of this register > since the bit indicating Gen4 capability is in USB4_SB_LINK_CONF (0x0c), > which is Rsvd on retimers regardless of the spec revision. A connected > port could easily have higher/lower capabilities, too. Checked again, the USB4_SB_FW_VERSION (0x02) register's lowest 8 bytes are 0/1 for retimers implementing USB4v1 and 2 for v2, so we may go this path too Konrad