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[129.46.96.20]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37265a179c1sm10908331eec.11.2026.11.09.01.00.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 01:00:52 -0800 (PST) Date: Mon, 9 Nov 2026 01:00:50 -0800 From: Peter Chen To: Akash Kumar Cc: Greg Kroah-Hartman , Bjorn Andersson , Konrad Dybcio , Rob Herring , Dmitry Baryshkov , Krzysztof Kozlowski , Conor Dooley , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v2] usb: dwc3: Update nominal max votes for qcom usb Message-ID: References: <20261105100626.2003771-1-akash.kumar@oss.qualcomm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105100626.2003771-1-akash.kumar@oss.qualcomm.com> X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA5MDAzNSBTYWx0ZWRfXxT+bLYD5xEl/ lgr+mnoVMDoyal1xgHb3FDOEeha+pKdmF+GlscACjzptmO2a+InzOPcwiKNJKOIavu5FPwh9rqm A5nm6JIy9EtVyyggMmvd5M9colzA/bbGBm6+oV/R4PuaXuqb6r3t3RMwhjpOzFE5O0/diUD9P2k QYdoEQ77IPp5NpjGeC9c8cqrxmntflhGNbP2hL6Vy0v7U/2ZeW002kMVu/qVB9vu8FVcHC7tJho aLsWLAnMOmo63XjiQACwAfO6iSAUiq6IpwuURUjSe0KDPZS0tJxjT6qWh/DS7LPKhThdVNwJvux XsBlpcFWbwYl3D1HlRWpULyQVuVYU3+YkS8L81b6rkIAouYCDxLqWcNC4PCeuYaEt+s2iT2XxGd D2TWdewqTfZGL+8Sbcex6mZwQilGPUVohjkUygUt6qIqGHrmfBIpOuOwp24OtvTenwogyJAh4M4 EOK+KcckLxakVRX+Idw== X-Proofpoint-ORIG-GUID: jzAoHWaYjs3TrdPpAlDkg0BxxkRkcQS2 X-Proofpoint-GUID: jzAoHWaYjs3TrdPpAlDkg0BxxkRkcQS2 X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA5MDAzNSBTYWx0ZWRfX+VMhqmaaIlq/ LksZrHGKVlz0JRQ6YVSQEquGKMKWxGSmeoUB3o9N9RPdBpH5ant1FkdJOevT2iAV4i2DGK/VKvv r2Dtg+DcIJsYMXKshMPVKrPoHh2Qx/U= X-Authority-Analysis: v=2.4 cv=V8LoQuni c=1 sm=1 tr=0 ts=6af18bc8 cx=c_pps a=Uww141gWH0fZj/3QKPojxA==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=kj9zAlcOel0A:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=rNO_JpGmdzbLC-vSDh4A:9 a=CjuIK1q_8ugA:10 a=PxkB5W3o20Ba91AHUih5:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-09_03,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1015 malwarescore=0 bulkscore=0 impostorscore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611090035 On 26-11-05 15:32:16, Akash Kumar wrote: > Increase the nominal max USB memory bandwidth vote to let DDR scale > higher within its nominal corner, fixing glitches seen during > simultaneous USB audio use cases. > > USB_MEMORY_PEAK_SS_BW is raised from 2500 MB/s to 4500 MB/s (+2000 > MB/s, ~1.8x). This ICC vote does not by itself determine DDR > frequency; the vote-to-frequency mapping is platform-specific and > comes from each target's interconnect/OPP table. On the tested > targets, the old vote kept DDR pinned at 1 GHz within the nominal > corner, even though DDR can run at 1.5 GHz (+50%) within the same > corner. At 1 GHz, glitches were observed during multiple concurrent > USB audio use cases. How we decide which value is suitable, eg, you set 4500 here? If DDR can run higher, and we have more stress test case like UAS transfer + UVC transfer, do we need this value to be higher? Is it okay we just set the highest value for USB, there is a platform OPP table, and we let ICC choose the highest value for USB at specific platform? Peter > > Tested internally on RB3, RB4, RB8, Shikra, and other KLM targets. > With the updated vote, DDR is allowed to run at the higher nominal > frequency, and the following were measured (not merely projected): > > - USB memory throughput: 125 MB/s -> 145 MB/s (+16%) > - RTD-USBC audio latency: 17.9 ms -> 16.6 ms (-7.3%) > > RTD-USBC is the round-trip audio latency measured over a USB-C audio > path; lower is better. Note the +50% DDR frequency headroom does not > map linearly to the +16% throughput gain, since throughput is also > bounded by other factors along the USB/DDR path; the frequency > increase is necessary but not sufficient to explain the full gain on > its own. > > Signed-off-by: Akash Kumar > --- > v2: Added Details of targets Tested. > Added details for usb vote. > Added KPI Details. > Dropped USB AVG BW vote change which is not needed. > > Link to v1: https://lore.kernel.org/all/20260611081831.2743464-1-akash.kumar@oss.qualcomm.com/ > --- > drivers/usb/dwc3/dwc3-qcom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c > index ac68b4218b56..3a19385969dc 100644 > --- a/drivers/usb/dwc3/dwc3-qcom.c > +++ b/drivers/usb/dwc3/dwc3-qcom.c > @@ -46,7 +46,7 @@ > #define USB_MEMORY_AVG_HS_BW MBps_to_icc(240) > #define USB_MEMORY_PEAK_HS_BW MBps_to_icc(700) > #define USB_MEMORY_AVG_SS_BW MBps_to_icc(1000) > -#define USB_MEMORY_PEAK_SS_BW MBps_to_icc(2500) > +#define USB_MEMORY_PEAK_SS_BW MBps_to_icc(4500) > #define APPS_USB_AVG_BW 0 > #define APPS_USB_PEAK_BW MBps_to_icc(40) > > -- > 2.43.0 > > -- Thanks, Peter Chen