[PATCH v2 2/5] usb: dwc3: reference clock period configuration

[Marek Vasut]

From: Balaji Prakash J <bjagadee at codeaurora.org>

Set reference clock period when it differs from dwc3 default hardware
set.

We could calculate clock period based on reference clock frequency. But
this information is not always available. This is the case of PCI bus
attached USB host. For that reason we use a custom property.

Tested (USB2 only) on IPQ6010 SoC based board with 24 MHz reference
clock while hardware default is 19.2 MHz.

[ baruch: rewrite commit message; drop GFLADJ code; remove 'quirk-' from
  property name; mention tested hardware ]

[ marek: Ported from Linux kernel commit
         7bee318838890 ("usb: dwc3: reference clock period configuration") ]

Signed-off-by: Balaji Prakash J <bjagadee at codeaurora.org>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
Signed-off-by: Marek Vasut <marex at denx.de> # Port from Linux
---
Cc: Angus Ainslie <angus at akkea.ca>
Cc: Bin Meng <bmeng.cn at gmail.com>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: Kunihiko Hayashi <hayashi.kunihiko at socionext.com>
Cc: Michal Simek <michal.simek at xilinx.com>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Sean Anderson <sean.anderson at seco.com>
Cc: Stefano Babic <sbabic at denx.de>
---
V2: No change
---
 drivers/usb/dwc3/core.c | 27 +++++++++++++++++++++++++++
 drivers/usb/dwc3/core.h |  6 ++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index b592a487e00..300450100c9 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -28,6 +28,7 @@
 #include <generic-phy.h>
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
+#include <linux/bitfield.h>
 
 #include "core.h"
 #include "gadget.h"
@@ -114,6 +115,28 @@ static void dwc3_frame_length_adjustment(struct dwc3 *dwc, u32 fladj)
 	dwc3_writel(dwc->regs, DWC3_GFLADJ, reg);
 }
 
+/**
+ * dwc3_ref_clk_period - Reference clock period configuration
+ *		Default reference clock period depends on hardware
+ *		configuration. For systems with reference clock that differs
+ *		from the default, this will set clock period in DWC3_GUCTL
+ *		register.
+ * @dwc: Pointer to our controller context structure
+ * @ref_clk_per: reference clock period in ns
+ */
+static void dwc3_ref_clk_period(struct dwc3 *dwc)
+{
+	u32 reg;
+
+	if (dwc->ref_clk_per == 0)
+		return;
+
+	reg = dwc3_readl(dwc->regs, DWC3_GUCTL);
+	reg &= ~DWC3_GUCTL_REFCLKPER_MASK;
+	reg |=  FIELD_PREP(DWC3_GUCTL_REFCLKPER_MASK, dwc->ref_clk_per);
+	dwc3_writel(dwc->regs, DWC3_GUCTL, reg);
+}
+
 /**
  * dwc3_free_one_event_buffer - Frees one event buffer
  * @dwc: Pointer to our controller context structure
@@ -640,6 +663,9 @@ static int dwc3_core_init(struct dwc3 *dwc)
 	/* Adjust Frame Length */
 	dwc3_frame_length_adjustment(dwc, dwc->fladj);
 
+	/* Adjust Reference Clock Period */
+	dwc3_ref_clk_period(dwc);
+
 	dwc3_set_incr_burst_type(dwc);
 
 	return 0;
@@ -1043,6 +1069,7 @@ void dwc3_of_parse(struct dwc3 *dwc)
 		| (dwc->is_utmi_l1_suspend << 4);
 
 	dev_read_u32(dev, "snps,quirk-frame-length-adjustment", &dwc->fladj);
+	dev_read_u32(dev, "snps,ref-clock-period-ns", &dwc->ref_clk_per);
 
 	/*
 	 * Handle property "snps,incr-burst-type-adjustment".
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 0d20fe285b0..b4a7d9e52bc 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -249,6 +249,10 @@
 #define DWC3_GFLADJ_30MHZ_SDBND_SEL		(1 << 7)
 #define DWC3_GFLADJ_30MHZ_MASK			0x3f
 
+/* Global User Control Register*/
+#define DWC3_GUCTL_REFCLKPER_MASK		0xffc00000
+#define DWC3_GUCTL_REFCLKPER_SEL		22
+
 /* Device Configuration Register */
 #define DWC3_DCFG_DEVADDR(addr)	((addr) << 3)
 #define DWC3_DCFG_DEVADDR_MASK	DWC3_DCFG_DEVADDR(0x7f)
@@ -671,6 +675,7 @@ struct dwc3_scratchpad_array {
  * @ref_clk: reference clock
  * @regs: base address for our registers
  * @regs_size: address space size
+ * @ref_clk_per: reference clock period configuration
  * @nr_scratch: number of scratch buffers
  * @num_event_buffers: calculated number of event buffers
  * @u1u2: only used on revisions <1.83a for workaround
@@ -832,6 +837,7 @@ struct dwc3 {
 	u8			lpm_nyet_threshold;
 	u8			hird_threshold;
 	u32			fladj;
+	u32			ref_clk_per;
 	u8			incrx_mode;
 	u32			incrx_size;
 
-- 
2.35.1