[PATCH v2 5/7] usb: dwc3: Add snps,ref-clock-frequency-hz property for ACPI

[Sean Anderson <sean.anderson@seco.com>]

This property allows setting the reference clock frequency properly for
ACPI-based systems. It is not documented under dt-bindings, since it is
not intended for use on DT-based systems. DT-based systems should use
the clocks property instead.

Frequency is preferred over period since it has greater precision when
used in calculations.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
---

Changes in v2:
- New

 drivers/usb/dwc3/core.c | 6 ++++--
 drivers/usb/dwc3/core.h | 4 +++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 883e119377f0..5f3dc5f6cbcb 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -350,8 +350,8 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc)
 	u32 reg;
 	unsigned long decr, fladj, rate, period;
 
-	if (dwc->ref_clk) {
-		rate = clk_get_rate(dwc->ref_clk);
+	if (dwc->ref_clk || dwc->ref_clk_freq) {
+		rate = clk_get_rate(dwc->ref_clk) ?: dwc->ref_clk_freq;
 		if (!rate)
 			return;
 		period = NSEC_PER_SEC / rate;
@@ -1492,6 +1492,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 				 &dwc->fladj);
 	device_property_read_u32(dev, "snps,ref-clock-period-ns",
 				 &dwc->ref_clk_per);
+	device_property_read_u32(dev, "snps,ref-clock-frequency-hz",
+				 &dwc->ref_clk_freq);
 
 	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 eb9c1efced05..00a792459fec 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -988,7 +988,8 @@ struct dwc3_scratchpad_array {
  * @regs: base address for our registers
  * @regs_size: address space size
  * @fladj: frame length adjustment
- * @ref_clk_per: reference clock period configuration
+ * @ref_clk_per: reference clock period; deprecated in favor of @ref_clk_freq
+ * @ref_clk_freq: reference clock frequency to use if @ref_clk is missing
  * @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
@@ -1171,6 +1172,7 @@ struct dwc3 {
 
 	u32			fladj;
 	u32			ref_clk_per;
+	u32			ref_clk_freq;
 	u32			irq_gadget;
 	u32			otg_irq;
 	u32			current_otg_role;
-- 
2.25.1