From: Sean Anderson sean.anderson@seco.com
GUCTL.REFCLKPER can only account for clock frequencies with integer periods. To address this, program REFCLK_FLADJ with the relative error caused by period truncation. The formula given in the register reference has been rearranged to allow calculation based on rate (instead of period), and to allow for fixed-point arithmetic.
Additionally, calculate a value for 240MHZDECR. This configures a simulated 240Mhz clock using a counter with one fractional bit (PLS1).
This register is programmed only for versions >= 2.50a, since this is the check also used by commit db2be4e9e30c ("usb: dwc3: Add frame length adjustment quirk").
Tested-by: Robert Hancock robert.hancock@calian.com Reviewed-by: Robert Hancock robert.hancock@calian.com Reviewed-by: Thinh Nguyen Thinh.Nguyen@synopsys.com Signed-off-by: Sean Anderson sean.anderson@seco.com Link: https://lore.kernel.org/r/20220127200636.1456175-5-sean.anderson@seco.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/dwc3/core.c | 39 ++++++++++++++++++++++++++++++++++++++- drivers/usb/dwc3/core.h | 3 +++ 2 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c index 6ee75a72c4d8..2eb27c60542a 100644 --- a/drivers/usb/dwc3/core.c +++ b/drivers/usb/dwc3/core.c @@ -356,6 +356,8 @@ static void dwc3_frame_length_adjustment(struct dwc3 *dwc) static void dwc3_ref_clk_period(struct dwc3 *dwc) { unsigned long period; + unsigned long fladj; + unsigned long decr; unsigned long rate; u32 reg;
@@ -366,6 +368,7 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) period = NSEC_PER_SEC / rate; } else if (dwc->ref_clk_per) { period = dwc->ref_clk_per; + rate = NSEC_PER_SEC / period; } else { return; } @@ -374,8 +377,42 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) reg &= ~DWC3_GUCTL_REFCLKPER_MASK; reg |= FIELD_PREP(DWC3_GUCTL_REFCLKPER_MASK, period); dwc3_writel(dwc->regs, DWC3_GUCTL, reg); -}
+ if (DWC3_VER_IS_PRIOR(DWC3, 250A)) + return; + + /* + * The calculation below is + * + * 125000 * (NSEC_PER_SEC / (rate * period) - 1) + * + * but rearranged for fixed-point arithmetic. The division must be + * 64-bit because 125000 * NSEC_PER_SEC doesn't fit in 32 bits (and + * neither does rate * period). + * + * Note that rate * period ~= NSEC_PER_SECOND, minus the number of + * nanoseconds of error caused by the truncation which happened during + * the division when calculating rate or period (whichever one was + * derived from the other). We first calculate the relative error, then + * scale it to units of 8 ppm. + */ + fladj = div64_u64(125000ULL * NSEC_PER_SEC, (u64)rate * period); + fladj -= 125000; + + /* + * The documented 240MHz constant is scaled by 2 to get PLS1 as well. + */ + decr = 480000000 / rate; + + reg = dwc3_readl(dwc->regs, DWC3_GFLADJ); + reg &= ~DWC3_GFLADJ_REFCLK_FLADJ_MASK + & ~DWC3_GFLADJ_240MHZDECR + & ~DWC3_GFLADJ_240MHZDECR_PLS1; + reg |= FIELD_PREP(DWC3_GFLADJ_REFCLK_FLADJ_MASK, fladj) + | FIELD_PREP(DWC3_GFLADJ_240MHZDECR, decr >> 1) + | FIELD_PREP(DWC3_GFLADJ_240MHZDECR_PLS1, decr & 1); + dwc3_writel(dwc->regs, DWC3_GFLADJ, reg); +}
/** * dwc3_free_one_event_buffer - Frees one event buffer diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h index 1e5ef1c512fb..9c421de4d01d 100644 --- a/drivers/usb/dwc3/core.h +++ b/drivers/usb/dwc3/core.h @@ -384,6 +384,9 @@ /* Global Frame Length Adjustment Register */ #define DWC3_GFLADJ_30MHZ_SDBND_SEL BIT(7) #define DWC3_GFLADJ_30MHZ_MASK 0x3f +#define DWC3_GFLADJ_REFCLK_FLADJ_MASK GENMASK(21, 8) +#define DWC3_GFLADJ_240MHZDECR GENMASK(30, 24) +#define DWC3_GFLADJ_240MHZDECR_PLS1 BIT(31)
/* Global User Control Register*/ #define DWC3_GUCTL_REFCLKPER_MASK 0xffc00000