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

[Peter Chen <peter.chen@oss.qualcomm.com>]

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.
> 
> 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>

Reviewed-by: Peter Chen <peter.chen@oss.qualcomm.com>

Peter
> ---
> 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