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SubjectRe: [PATCH v12 3/6] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements
On Fri, Jul 02, 2021 at 02:37:32AM -0700, Wesley Cheng wrote:
> Some devices have USB compositions which may require multiple endpoints
> that support EP bursting. HW defined TX FIFO sizes may not always be
> sufficient for these compositions. By utilizing flexible TX FIFO
> allocation, this allows for endpoints to request the required FIFO depth to
> achieve higher bandwidth. With some higher bMaxBurst configurations, using
> a larger TX FIFO size results in better TX throughput.
>
> By introducing the check_config() callback, the resizing logic can fetch
> the maximum number of endpoints used in the USB composition (can contain
> multiple configurations), which helps ensure that the resizing logic can
> fulfill the configuration(s), or return an error to the gadget layer
> otherwise during bind time.
>
> Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
> ---
> drivers/usb/dwc3/core.c | 9 ++
> drivers/usb/dwc3/core.h | 15 ++++
> drivers/usb/dwc3/ep0.c | 2 +
> drivers/usb/dwc3/gadget.c | 221 ++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 247 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index e0a8e79..a7bcdb9d 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1267,6 +1267,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> u8 rx_max_burst_prd;
> u8 tx_thr_num_pkt_prd;
> u8 tx_max_burst_prd;
> + u8 tx_fifo_resize_max_num;
> const char *usb_psy_name;
> int ret;
>
> @@ -1282,6 +1283,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> */
> hird_threshold = 12;
>
> + tx_fifo_resize_max_num = 6;
> +

No comment as to why 6 was picked, like the other defaults in this
function?

Why was 6 picked?


> dwc->maximum_speed = usb_get_maximum_speed(dev);
> dwc->max_ssp_rate = usb_get_maximum_ssp_rate(dev);
> dwc->dr_mode = usb_get_dr_mode(dev);
> @@ -1325,6 +1328,10 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> &tx_thr_num_pkt_prd);
> device_property_read_u8(dev, "snps,tx-max-burst-prd",
> &tx_max_burst_prd);
> + dwc->do_fifo_resize = device_property_read_bool(dev,
> + "tx-fifo-resize");
> + device_property_read_u8(dev, "tx-fifo-max-num",
> + &tx_fifo_resize_max_num);

So you overwrite the "max" with whatever is given to you? What if
tx-fifo-resize is not enabled?

thanks,

greg k-h

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