On Tue, 26 Feb 2013, Paul Zimmerman wrote:
> These files contain the HCD code, and implement the Linux
> hc_driver API. Support for both slave mode and buffer DMA mode
> of the controller is included.
>
> Signed-off-by: Paul Zimmerman <[email protected]>
...
> +#define BITSTUFFTIME(bytecount) ((8 * 7 * (bytecount)) / 6)
> +#define HS_HOST_DELAY 5 /* nanoseconds */
> +#define FS_LS_HOST_DELAY 1000 /* nanoseconds */
> +#define HUB_LS_SETUP 333 /* nanoseconds */
> +
> +static u32 dwc2_calc_bus_time(struct dwc2_hsotg *hsotg, int speed, int is_in,
> + int is_isoc, int bytecount)
> +{
> + unsigned long retval;
> +
> + switch (speed) {
> + case USB_SPEED_HIGH:
> + if (is_isoc)
> + retval =
> + ((38 * 8 * 2083) +
> + (2083 * (3 + BITSTUFFTIME(bytecount)))) / 1000 +
> + HS_HOST_DELAY;
> + else
> + retval =
> + ((55 * 8 * 2083) +
> + (2083 * (3 + BITSTUFFTIME(bytecount)))) / 1000 +
> + HS_HOST_DELAY;
> + break;
> + case USB_SPEED_FULL:
> + if (is_isoc) {
> + retval =
> + (8354 * (31 + 10 * BITSTUFFTIME(bytecount))) / 1000;
> + if (is_in)
> + retval = 7268 + FS_LS_HOST_DELAY + retval;
> + else
> + retval = 6265 + FS_LS_HOST_DELAY + retval;
> + } else {
> + retval =
> + (8354 * (31 + 10 * BITSTUFFTIME(bytecount))) / 1000;
> + retval = 9107 + FS_LS_HOST_DELAY + retval;
> + }
> + break;
> + case USB_SPEED_LOW:
> + if (is_in) {
> + retval =
> + (67667 * (31 + 10 * BITSTUFFTIME(bytecount))) /
> + 1000;
> + retval =
> + 64060 + (2 * HUB_LS_SETUP) + FS_LS_HOST_DELAY +
> + retval;
> + } else {
> + retval =
> + (66700 * (31 + 10 * BITSTUFFTIME(bytecount))) /
> + 1000;
> + retval =
> + 64107 + (2 * HUB_LS_SETUP) + FS_LS_HOST_DELAY +
> + retval;
> + }
> + break;
> + default:
> + dev_warn(hsotg->dev, "Unknown device speed\n");
> + retval = -1;
> + }
> +
> + return NS_TO_US(retval);
> +}
Is there some specific reason for rolling your own version of
usb_calc_bus_time()?
I presume you copied these timing values from the USB spec. Note that
the formulas in the spec are full of mistakes. At some point I will
submit corrections to the core routine, along with a document
explaining how they are calculated. But if you have your own separate
timing routine like this, I won't change it.
Alan Stern
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