On Sat, 2022-01-08 at 00:17 +0000, Thinh Nguyen wrote: > Robert Hancock wrote: > > Previously a device tree property was added to allow overriding the > > reference clock period parameter if the default value used was incorrect. > > However, there is another register field, GFLADJ_REFCLK_FLADJ, which > > reflects the fractional nanosecond portion of the reference clock > > period. Add a snps,ref-clock-fladj property to allow configuring this > > as well. > > > > On the Xilinx ZynqMP platform, the reference clock appears to always > > be 20 MHz, giving a clock period of 50 ns. However, the default value > > of GFLADJ_REFCLK_FLADJ was 1008 rather than 0 as it should have been, > > which prevented many USB devices from functioning properly. The > > psu_init code run by the Xilinx first-stage boot loader sets this > > value to 0, however when the controller is reset by the dwc3-xilinx > > layer, the incorrect default value is restored. This configuration > > property allows ensuring that the correct value is always used. > > > > Signed-off-by: Robert Hancock <robert.hancock@xxxxxxxxxx> > > --- > > drivers/usb/dwc3/core.c | 32 ++++++++++++++++++++++++++++++++ > > drivers/usb/dwc3/core.h | 3 +++ > > 2 files changed, 35 insertions(+) > > > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > > index f4c09951b517..6289fbcbad45 100644 > > --- a/drivers/usb/dwc3/core.c > > +++ b/drivers/usb/dwc3/core.c > > @@ -359,6 +359,34 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) > > } > > > > > > +/* > > Use kernel doc style "/**" Will update in v2. > > > + * dwc3_ref_clk_fladj - Reference clock period (fractional portion) > > configuration > > + * GFLADJ_REFCLK_FLADJ contains the fractional portion of the reference > > clock > > + * period set in GUCTL_REFCLKPER. > > It's not a direct "fractional portion" the way it's described here. It > may cause some confusion. Let's use the word adjustment to account for > the fractional portion that's calculated as below. > > > + * Calculated as: ((125000/ref_clk_period_integer)- > > (125000/ref_clk_period)) * ref_clk_period > > Note that ref_clk_period_integer is the value in GUCTL.REFCLKPER, and > the "ref_clk_period" is the period with fractional value. Rewording this for v2. > > > + * This value can be specified in the device tree if the default value is > > incorrect. > > + * Note that 0 is a valid value. > > + * > > + * @dwc3: Pointer to our controller context structure > > + */ > > +static void dwc3_ref_clk_fladj(struct dwc3 *dwc) > > +{ > > + u32 reg, reg_new; > > I believe Felipe prefers to declare them in separate lines. Let's keep > it consistent as how we do it in for this driver. Will do. > > > + > > + if (DWC3_VER_IS_PRIOR(DWC3, 250A)) > > + return; > > + > > + if (!dwc->ref_clk_fladj_set) > > + return; > > + > > + reg = dwc3_readl(dwc->regs, DWC3_GFLADJ); > > + reg_new = reg & ~DWC3_GFLADJ_REFCLK_FLADJ_MASK; > > + reg_new |= FIELD_PREP(DWC3_GFLADJ_REFCLK_FLADJ_MASK, dwc- > > >ref_clk_fladj); > > + if (reg_new != reg) > > + dwc3_writel(dwc->regs, DWC3_GFLADJ, reg_new); > > +} > > + > > + > > /** > > * dwc3_free_one_event_buffer - Frees one event buffer > > * @dwc: Pointer to our controller context structure > > @@ -1033,6 +1061,7 @@ static int dwc3_core_init(struct dwc3 *dwc) > > > > /* Adjust Reference Clock Period */ > > dwc3_ref_clk_period(dwc); > > + dwc3_ref_clk_fladj(dwc); > > > > dwc3_set_incr_burst_type(dwc); > > > > @@ -1418,6 +1447,9 @@ static void dwc3_get_properties(struct dwc3 *dwc) > > &dwc->fladj); > > device_property_read_u32(dev, "snps,ref-clock-period-ns", > > &dwc->ref_clk_per); > > + if (!device_property_read_u32(dev, "snps,ref-clock-fladj", > > + &dwc->ref_clk_fladj)) > > + dwc->ref_clk_fladj_set = true; > > Please document it in the dwc3 DT file whenever we introduce a new property. Whoops, forgot that. Will add as a separate patch in v2. > > Also, do we need to add a new dwc->ref_clk_fladj_set? Can we just define > some default value for dwc->ref_clk_fladj as unspecified and have the > driver check against that (e.g. #define DWC3_REFCLK_FLADJ_UNSPECIFIED > 0xffffffff). I figured this was the most explicit/cleanest way to do it that would work with the default zero initialization of the structure. Most of these other settings seem to use 0 as the "don't change anything" value but in this case we do sometimes need to override the value with 0. > > Thanks, > Thinh > > > > > dwc->dis_metastability_quirk = device_property_read_bool(dev, > > "snps,dis_metastability_quirk"); > > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h > > index e1cc3f7398fb..650d4c2e7a67 100644 > > --- a/drivers/usb/dwc3/core.h > > +++ b/drivers/usb/dwc3/core.h > > @@ -388,6 +388,7 @@ > > /* 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 0x3fff00 > > > > /* Global User Control Register*/ > > #define DWC3_GUCTL_REFCLKPER_MASK 0xffc00000 > > @@ -1166,6 +1167,8 @@ struct dwc3 { > > > > u32 fladj; > > u32 ref_clk_per; > > + bool ref_clk_fladj_set; > > + u32 ref_clk_fladj; > > u32 irq_gadget; > > u32 otg_irq; > > u32 current_otg_role;