| Message ID | 20220114044230.2677283-5-robert.hancock@calian.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Xilinx ZynqMP USB fixes | expand |
Hi Robert, On 1/13/22 11:42 PM, 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. > > Reviewed-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com> > Signed-off-by: Robert Hancock <robert.hancock@calian.com> > --- > drivers/usb/dwc3/core.c | 35 +++++++++++++++++++++++++++++++++++ > drivers/usb/dwc3/core.h | 5 +++++ > 2 files changed, 40 insertions(+) > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > index f4c09951b517..ad224fb8088e 100644 > --- a/drivers/usb/dwc3/core.c > +++ b/drivers/usb/dwc3/core.c > @@ -359,6 +359,37 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) > } > > > +/** > + * dwc3_ref_clk_fladj - Reference clock period adjustment configuration > + * @dwc: Pointer to our controller context structure > + * > + * GFLADJ_REFCLK_FLADJ should be set based on the fractional portion of the > + * reference clock period, where the integer portion is set in GUCTL_REFCLKPER. > + * Calculated as: ((125000/ref_clk_period_integer)-(125000/ref_clk_period)) * ref_clk_period > + * where ref_clk_period_integer is the period specified in GUCTL_REFCLKPER and > + * ref_clk_period is the period including fractional value. > + * This value can be specified in the device tree if the default value is incorrect. > + * Note that 0 is a valid value. > + */ > +static void dwc3_ref_clk_fladj(struct dwc3 *dwc) > +{ > + u32 reg; > + u32 reg_new; > + > + 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 +1064,7 @@ 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 +1450,9 @@ 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; > > 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..5011296786de 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 > @@ -985,6 +986,8 @@ struct dwc3_scratchpad_array { > * @regs_size: address space size > * @fladj: frame length adjustment > * @ref_clk_per: reference clock period configuration > + * @ref_clk_fladj_set: whether ref_clk_fladj value is set/valid > + * @ref_clk_fladj: reference clock period fractional adjustment > * @irq_gadget: peripheral controller's IRQ number > * @otg_irq: IRQ number for OTG IRQs > * @current_otg_role: current role of operation while using the OTG block > @@ -1166,6 +1169,8 @@ 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; > Doesn't this property already exist as snps,quirk-frame-length-adjustment? --- I realize the cat is already out of the bag, but this seems like something which could be better modeled with a frequency property, or by using a clock. With these bindings, the board maintainer has to determine the reference clock frequency and then manually calculate the fractional adjustment. If the reference clock is ever changed (e.g. in a new board revision), the maintainer must then update two properties. However, Linux could calculate all this automatically. We already have a clock input for the reference with which we can determine the frequency (according to bindings/usb/snps,dwc3.yaml, though I cannot see where it is implemented in the driver). Even on platforms without a reference clock (such as USB over PCIe [1]), one can just add a fixed-rate clock to act as the reference. --Sean [1] https://lore.kernel.org/all/9f399bdf1ff752e31ab7497e3d5ce19bbb3ff247.1630389452.git.baruch@tkos.co.il/
On Fri, 2022-01-14 at 13:05 -0500, Sean Anderson wrote: > Hi Robert, > > On 1/13/22 11:42 PM, 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. > > > > Reviewed-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com> > > Signed-off-by: Robert Hancock <robert.hancock@calian.com> > > --- > > drivers/usb/dwc3/core.c | 35 +++++++++++++++++++++++++++++++++++ > > drivers/usb/dwc3/core.h | 5 +++++ > > 2 files changed, 40 insertions(+) > > > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > > index f4c09951b517..ad224fb8088e 100644 > > --- a/drivers/usb/dwc3/core.c > > +++ b/drivers/usb/dwc3/core.c > > @@ -359,6 +359,37 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) > > } > > > > > > +/** > > + * dwc3_ref_clk_fladj - Reference clock period adjustment configuration > > + * @dwc: Pointer to our controller context structure > > + * > > + * GFLADJ_REFCLK_FLADJ should be set based on the fractional portion of > > the > > + * reference clock period, where the integer portion is set in > > GUCTL_REFCLKPER. > > + * Calculated as: ((125000/ref_clk_period_integer)- > > (125000/ref_clk_period)) * ref_clk_period > > + * where ref_clk_period_integer is the period specified in GUCTL_REFCLKPER > > and > > + * ref_clk_period is the period including fractional value. > > + * This value can be specified in the device tree if the default value is > > incorrect. > > + * Note that 0 is a valid value. > > + */ > > +static void dwc3_ref_clk_fladj(struct dwc3 *dwc) > > +{ > > + u32 reg; > > + u32 reg_new; > > + > > + 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 +1064,7 @@ 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 +1450,9 @@ 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; > > > > 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..5011296786de 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 > > @@ -985,6 +986,8 @@ struct dwc3_scratchpad_array { > > * @regs_size: address space size > > * @fladj: frame length adjustment > > * @ref_clk_per: reference clock period configuration > > + * @ref_clk_fladj_set: whether ref_clk_fladj value is set/valid > > + * @ref_clk_fladj: reference clock period fractional adjustment > > * @irq_gadget: peripheral controller's IRQ number > > * @otg_irq: IRQ number for OTG IRQs > > * @current_otg_role: current role of operation while using the OTG block > > @@ -1166,6 +1169,8 @@ 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; > > > > Doesn't this property already exist as snps,quirk-frame-length-adjustment? No, it's actually a different setting, though it's a bit confusing (kind of reflecting that the actual register settings are a bit confusing): snps,ref-clock-period-ns and snps,ref-clock-fladj specify the reference clock period (the whole nanoseconds and the fractional portion respectively). snps,quirk-frame-length-adjustment is another setting which seems to reflect the frame length according to a 30 MHz clock, and which overrides another input value that's provided to the core in hardware. (That's my understanding anyway, just based on the register descriptions in the ZynqMP documentation. The Synopsys guys might have a better idea what this actually does.) > > --- > > I realize the cat is already out of the bag, but this seems like > something which could be better modeled with a frequency property, or by > using a clock. With these bindings, the board maintainer has to > determine the reference clock frequency and then manually calculate the > fractional adjustment. If the reference clock is ever changed (e.g. in > a new board revision), the maintainer must then update two properties. > However, Linux could calculate all this automatically. > > We already have a clock input for the reference with which we can > determine the frequency (according to bindings/usb/snps,dwc3.yaml, > though I cannot see where it is implemented in the driver). Even on > platforms without a reference clock (such as USB over PCIe [1]), one can > just add a fixed-rate clock to act as the reference. That probably would make some sense.. the complication is that at least looking at the ZynqMP setup for this USB core, in the device tree the top-level zynqmp- dwc3 "wrapper" driver (drivers/usb/dwc3/dwc3-xilinx.c) is the one that has the clocks mapped to it right now, not the actual snps,dwc3 device that this driver is operating with. Other dwc3 variants like exynos, imx8mp, qcom etc. seem to be set up similarly. I'm not actually sure why it was setup this way with a parent and child device node with separate drivers, rather than just having device-specific extensions in the dwc3 driver for implementations that need it. But I'm guessing there's probably enough device tree references to that setup that we're stuck with it now. Simplified example: usb0: usb@ff9d0000 { compatible = "xlnx,zynqmp-dwc3"; clock-names = "bus_clk", "ref_clk"; clocks = <&zynqmp_clk USB0_BUS_REF>, <&zynqmp_clk USB3_DUAL_REF>; dwc3_0: usb@fe200000 { compatible = "snps,dwc3"; snps,quirk-frame-length-adjustment = <0x20>; snps,ref-clock-period-ns = <50>; snps,ref-clock-fladj = <0>; }; }; I'm pretty sure that the "ref_clk" clock on the zynqmp-dwc3 device is what snps,dwc3 calls the "ref" clock which these period settings are dealing with, and currently doesn't do anything with in its code if it's provided, other than enabling it. As you say, the driver could just pull out the rate of that clock and calculate the correct clock period values on its own. But given that properties need to be added to the device tree to support the current approach anyway, I guess the device tree should just add the ref clock into the child node as well.. > > --Sean > > [1] > https://urldefense.com/v3/__https://lore.kernel.org/all/9f399bdf1ff752e31ab7497e3d5ce19bbb3ff247.1630389452.git.baruch@tkos.co.il/__;!!IOGos0k!ytRCRnO1vDXkVSV3Nz06dhYdT5kiZU75gcjcs0bPss2UQM4mSwij8Wglzdem3ctNH5g$ >
On 1/14/22 2:22 PM, Robert Hancock wrote: > On Fri, 2022-01-14 at 13:05 -0500, Sean Anderson wrote: >> Hi Robert, >> >> On 1/13/22 11:42 PM, 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. >> > >> > Reviewed-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com> >> > Signed-off-by: Robert Hancock <robert.hancock@calian.com> >> > --- >> > drivers/usb/dwc3/core.c | 35 +++++++++++++++++++++++++++++++++++ >> > drivers/usb/dwc3/core.h | 5 +++++ >> > 2 files changed, 40 insertions(+) >> > >> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c >> > index f4c09951b517..ad224fb8088e 100644 >> > --- a/drivers/usb/dwc3/core.c >> > +++ b/drivers/usb/dwc3/core.c >> > @@ -359,6 +359,37 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) >> > } >> > >> > >> > +/** >> > + * dwc3_ref_clk_fladj - Reference clock period adjustment configuration >> > + * @dwc: Pointer to our controller context structure >> > + * >> > + * GFLADJ_REFCLK_FLADJ should be set based on the fractional portion of >> > the >> > + * reference clock period, where the integer portion is set in >> > GUCTL_REFCLKPER. >> > + * Calculated as: ((125000/ref_clk_period_integer)- >> > (125000/ref_clk_period)) * ref_clk_period >> > + * where ref_clk_period_integer is the period specified in GUCTL_REFCLKPER >> > and >> > + * ref_clk_period is the period including fractional value. >> > + * This value can be specified in the device tree if the default value is >> > incorrect. >> > + * Note that 0 is a valid value. >> > + */ >> > +static void dwc3_ref_clk_fladj(struct dwc3 *dwc) >> > +{ >> > + u32 reg; >> > + u32 reg_new; >> > + >> > + 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 +1064,7 @@ 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 +1450,9 @@ 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; >> > >> > 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..5011296786de 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 >> > @@ -985,6 +986,8 @@ struct dwc3_scratchpad_array { >> > * @regs_size: address space size >> > * @fladj: frame length adjustment >> > * @ref_clk_per: reference clock period configuration >> > + * @ref_clk_fladj_set: whether ref_clk_fladj value is set/valid >> > + * @ref_clk_fladj: reference clock period fractional adjustment >> > * @irq_gadget: peripheral controller's IRQ number >> > * @otg_irq: IRQ number for OTG IRQs >> > * @current_otg_role: current role of operation while using the OTG block >> > @@ -1166,6 +1169,8 @@ 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; >> > >> >> Doesn't this property already exist as snps,quirk-frame-length-adjustment? > > No, it's actually a different setting, though it's a bit confusing (kind of > reflecting that the actual register settings are a bit confusing): > > snps,ref-clock-period-ns and snps,ref-clock-fladj specify the reference clock > period (the whole nanoseconds and the fractional portion respectively). > > snps,quirk-frame-length-adjustment is another setting which seems to reflect > the frame length according to a 30 MHz clock, and which overrides another input > value that's provided to the core in hardware. (That's my understanding anyway, > just based on the register descriptions in the ZynqMP documentation. The > Synopsys guys might have a better idea what this actually does.) I think it does the same thing, but when GFLADJ_REFCLK_LPM_SEL=0. Its description is > This field indicates the value that is used for frame length > adjustment instead of considering from the sideband input signal > fladj_30mhz_reg and the description for GFLADJ_REFCLK_FLADJ is > This field indicates the frame length adjustment to be applied when > SOF/ITP counter is running on the ref_clk. This register value is used > to adjust the ITP interval when GCTL[SOFITPSYNC] is set to '1'; SOF > and ITP interval when GLADJ.GFLADJ_REFCLK_LPM_SEL is set to '1'. Although it's possible that these are different aspects (interval vs length?). According to the xHCI standard section 5.2.4, "the default value [of GFLADJ_30MHZ] is decimal 32 (20h), which gives a SOF cycle time of 60000." All in-tree bindings which set this property just set it to 0x20, so maybe we should just remove the binding and set it all the time. >> >> --- >> >> I realize the cat is already out of the bag, but this seems like >> something which could be better modeled with a frequency property, or by >> using a clock. With these bindings, the board maintainer has to >> determine the reference clock frequency and then manually calculate the >> fractional adjustment. If the reference clock is ever changed (e.g. in >> a new board revision), the maintainer must then update two properties. >> However, Linux could calculate all this automatically. >> >> We already have a clock input for the reference with which we can >> determine the frequency (according to bindings/usb/snps,dwc3.yaml, >> though I cannot see where it is implemented in the driver). Even on >> platforms without a reference clock (such as USB over PCIe [1]), one can >> just add a fixed-rate clock to act as the reference. > > That probably would make some sense.. the complication is that at least looking > at the ZynqMP setup for this USB core, in the device tree the top-level zynqmp- > dwc3 "wrapper" driver (drivers/usb/dwc3/dwc3-xilinx.c) is the one that has the > clocks mapped to it right now, not the actual snps,dwc3 device that this driver > is operating with. Other dwc3 variants like exynos, imx8mp, qcom etc. seem to > be set up similarly. > > I'm not actually sure why it was setup this way with a parent and child device > node with separate drivers, rather than just having device-specific extensions > in the dwc3 driver for implementations that need it. But I'm guessing there's > probably enough device tree references to that setup that we're stuck with it > now. I believe the motivation is that several of these drivers have auxiliary registers and rather than creating a second entry in `regs`, the original authors created sub-nodes instead. > Simplified example: > > usb0: usb@ff9d0000 { > compatible = "xlnx,zynqmp-dwc3"; > clock-names > = "bus_clk", "ref_clk"; > clocks = <&zynqmp_clk USB0_BUS_REF>, <&zynqmp_clk > USB3_DUAL_REF>; > > dwc3_0: usb@fe200000 { > compatible = "snps,dwc3"; > snps,quirk-frame-length-adjustment = <0x20>; > snps,ref-clock-period-ns = <50>; > snps,ref-clock-fladj = <0>; > }; > }; > > > I'm pretty sure that the "ref_clk" clock on the zynqmp-dwc3 device is what > snps,dwc3 calls the "ref" clock which these period settings are dealing with, > and currently doesn't do anything with in its code if it's provided, other than > enabling it. As you say, the driver could just pull out the rate of that clock > and calculate the correct clock period values on its own. I believe that's correct. On my system, ref_clk is set to usb3_dual_ref, which is running at 20MHz. > But given that properties need to be added to the device tree to support the > current approach anyway, I guess the device tree should just add the ref clock > into the child node as well.. I think that's a good idea. For existing bindings, we can create a fixed-rate clock based on snps,ref-clock-period-ns (and mark that property as deprecated). --Sean
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c index f4c09951b517..ad224fb8088e 100644 --- a/drivers/usb/dwc3/core.c +++ b/drivers/usb/dwc3/core.c @@ -359,6 +359,37 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc) } +/** + * dwc3_ref_clk_fladj - Reference clock period adjustment configuration + * @dwc: Pointer to our controller context structure + * + * GFLADJ_REFCLK_FLADJ should be set based on the fractional portion of the + * reference clock period, where the integer portion is set in GUCTL_REFCLKPER. + * Calculated as: ((125000/ref_clk_period_integer)-(125000/ref_clk_period)) * ref_clk_period + * where ref_clk_period_integer is the period specified in GUCTL_REFCLKPER and + * ref_clk_period is the period including fractional value. + * This value can be specified in the device tree if the default value is incorrect. + * Note that 0 is a valid value. + */ +static void dwc3_ref_clk_fladj(struct dwc3 *dwc) +{ + u32 reg; + u32 reg_new; + + 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 +1064,7 @@ 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 +1450,9 @@ 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; 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..5011296786de 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 @@ -985,6 +986,8 @@ struct dwc3_scratchpad_array { * @regs_size: address space size * @fladj: frame length adjustment * @ref_clk_per: reference clock period configuration + * @ref_clk_fladj_set: whether ref_clk_fladj value is set/valid + * @ref_clk_fladj: reference clock period fractional adjustment * @irq_gadget: peripheral controller's IRQ number * @otg_irq: IRQ number for OTG IRQs * @current_otg_role: current role of operation while using the OTG block @@ -1166,6 +1169,8 @@ 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;