[PATCH v4, 3/3] usb: dwc3: core: Workaround for CSR read timeout

[joswang]

From: Jos Wang <joswang@xxxxxxxxxx>

This is a workaround for STAR 4846132, which only affects
DWC_usb31 version2.00a operating in host mode.

There is a problem in DWC_usb31 version 2.00a operating
in host mode that would cause a CSR read timeout When CSR
read coincides with RAM Clock Gating Entry. By disable
Clock Gating, sacrificing power consumption for normal
operation.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jos Wang <joswang@xxxxxxxxxx>
---
v1 -> v2:
- add "dt-bindings: usb: dwc3: Add snps,p2p3tranok quirk" patch,
  this patch does not make any changes
v2 -> v3:
- code refactor
- modify comment, add STAR number, workaround applied in host mode
- modify commit message, add STAR number, workaround applied in host mode
- modify Author Jos Wang
v3 -> v4:
- modify commit message, add Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/usb/dwc3/core.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 3a8fbc2d6b99..61f858f64e5a 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -960,12 +960,16 @@ static bool dwc3_core_is_valid(struct dwc3 *dwc)
 
 static void dwc3_core_setup_global_control(struct dwc3 *dwc)
 {
+	unsigned int power_opt;
+	unsigned int hw_mode;
 	u32 reg;
 
 	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
 	reg &= ~DWC3_GCTL_SCALEDOWN_MASK;
+	hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
+	power_opt = DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1);
 
-	switch (DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1)) {
+	switch (power_opt) {
 	case DWC3_GHWPARAMS1_EN_PWROPT_CLK:
 		/**
 		 * WORKAROUND: DWC3 revisions between 2.10a and 2.50a have an
@@ -998,6 +1002,20 @@ static void dwc3_core_setup_global_control(struct dwc3 *dwc)
 		break;
 	}
 
+	/*
+	 * This is a workaround for STAR#4846132, which only affects
+	 * DWC_usb31 version2.00a operating in host mode.
+	 *
+	 * There is a problem in DWC_usb31 version 2.00a operating
+	 * in host mode that would cause a CSR read timeout When CSR
+	 * read coincides with RAM Clock Gating Entry. By disable
+	 * Clock Gating, sacrificing power consumption for normal
+	 * operation.
+	 */
+	if (power_opt != DWC3_GHWPARAMS1_EN_PWROPT_NO &&
+	    hw_mode != DWC3_GHWPARAMS0_MODE_GADGET && DWC3_VER_IS(DWC31, 200A))
+		reg |= DWC3_GCTL_DSBLCLKGTNG;
+
 	/* check if current dwc3 is on simulation board */
 	if (dwc->hwparams.hwparams6 & DWC3_GHWPARAMS6_EN_FPGA) {
 		dev_info(dwc->dev, "Running with FPGA optimizations\n");
-- 
2.17.1