[PATCH v2 5/9] usb: dwc3: Add frame length adjustment quirk

[Michael Walle]

[backport from linux commit db2be4e9e30c6e43e48c5749d3fc74cee0a6bbb3]

Add adjust_frame_length_quirk for writing to fladj register
which adjusts (micro)frame length to value provided by
"snps,quirk-frame-length-adjustment" property thus avoiding
USB 2.0 devices to time-out over a longer run

Signed-off-by: Michael Walle <mich...@walle.cc>
---
 drivers/usb/dwc3/core.c | 26 ++++++++++++++++++++++++++
 drivers/usb/dwc3/core.h |  6 ++++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index dfd7cf683f..4fb6b59d50 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -93,6 +93,27 @@ static int dwc3_core_soft_reset(struct dwc3 *dwc)
        return 0;
 }
 
+/*
+ * dwc3_frame_length_adjustment - Adjusts frame length if required
+ * @dwc3: Pointer to our controller context structure
+ * @fladj: Value of GFLADJ_30MHZ to adjust frame length
+ */
+static void dwc3_frame_length_adjustment(struct dwc3 *dwc, u32 fladj)
+{
+       u32 reg;
+
+       if (dwc->revision < DWC3_REVISION_250A)
+               return;
+
+       if (fladj == 0)
+               return;
+
+       reg = dwc3_readl(dwc->regs, DWC3_GFLADJ);
+       reg &= ~DWC3_GFLADJ_30MHZ_MASK;
+       reg |= DWC3_GFLADJ_30MHZ_SDBND_SEL | fladj;
+       dwc3_writel(dwc->regs, DWC3_GFLADJ, reg);
+}
+
 /**
  * dwc3_free_one_event_buffer - Frees one event buffer
  * @dwc: Pointer to our controller context structure
@@ -569,6 +590,9 @@ static int dwc3_core_init(struct dwc3 *dwc)
        if (ret)
                goto err1;
 
+       /* Adjust Frame Length */
+       dwc3_frame_length_adjustment(dwc, dwc->fladj);
+
        return 0;
 
 err1:
@@ -958,6 +982,8 @@ void dwc3_of_parse(struct dwc3 *dwc)
 
        dwc->hird_threshold = hird_threshold
                | (dwc->is_utmi_l1_suspend << 4);
+
+       dev_read_u32(dev, "snps,quirk-frame-length-adjustment", &dwc->fladj);
 }
 
 int dwc3_init(struct dwc3 *dwc)
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 1502cb859a..62e4df74fa 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -115,6 +115,7 @@
 #define DWC3_GEVNTCOUNT(n)     (0xc40c + (n * 0x10))
 
 #define DWC3_GHWPARAMS8                0xc600
+#define DWC3_GFLADJ            0xc630
 
 /* Device Registers */
 #define DWC3_DCFG              0xc700
@@ -233,6 +234,10 @@
 /* Global HWPARAMS6 Register */
 #define DWC3_GHWPARAMS6_EN_FPGA                        (1 << 7)
 
+/* Global Frame Length Adjustment Register */
+#define DWC3_GFLADJ_30MHZ_SDBND_SEL            (1 << 7)
+#define DWC3_GFLADJ_30MHZ_MASK                 0x3f
+
 /* Device Configuration Register */
 #define DWC3_DCFG_DEVADDR(addr)        ((addr) << 3)
 #define DWC3_DCFG_DEVADDR_MASK DWC3_DCFG_DEVADDR(0x7f)
@@ -812,6 +817,7 @@ struct dwc3 {
        u8                      test_mode_nr;
        u8                      lpm_nyet_threshold;
        u8                      hird_threshold;
+       u32                     fladj;
 
        unsigned                delayed_status:1;
        unsigned                ep0_bounced:1;
-- 
2.30.2