[PATCH v2] usb: dwc3: Update nominal max votes for qcom usb

[Akash Kumar <akash.kumar@oss.qualcomm.com>]

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.

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 <akash.kumar@oss.qualcomm.com>
---
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