linux-kernel - [PATCH v2 1/3] usb: dwc3: ulpi: Use VStsDone to detect PHY regs access completion

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Message-ID: <20201026164050.30380-2-Sergey.Semin@baikalelectronics.ru>
Date:   Mon, 26 Oct 2020 19:40:48 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        David Cohen <david.a.cohen@...ux.intel.com>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 1/3] usb: dwc3: ulpi: Use VStsDone to detect PHY regs access completion

In accordance with [1] the DWC_usb3 core sets the GUSB2PHYACCn.VStsDone
bit when the PHY vendor control access is done and clears it when the
application initiates a new transaction. The doc doesn't say anything
about the GUSB2PHYACCn.VStsBsy flag serving for the same purpose. Moreover
we've discovered that the VStsBsy flag can be cleared before the VStsDone
bit. So using the former as a signal of the PHY control registers
completion might be dangerous. Let's have the VStsDone flag utilized
instead then.

[1] Synopsys DesignWare Cores SuperSpeed USB 3.0 xHCI Host Controller
    Databook, 2.70a, December 2013, p.388

Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
---
 drivers/usb/dwc3/core.h | 1 +
 drivers/usb/dwc3/ulpi.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 2f04b3e42bf1..8d5e5bba1bc2 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -284,6 +284,7 @@
 
 /* Global USB2 PHY Vendor Control Register */
 #define DWC3_GUSB2PHYACC_NEWREGREQ	BIT(25)
+#define DWC3_GUSB2PHYACC_DONE		BIT(24)
 #define DWC3_GUSB2PHYACC_BUSY		BIT(23)
 #define DWC3_GUSB2PHYACC_WRITE		BIT(22)
 #define DWC3_GUSB2PHYACC_ADDR(n)	(n << 16)
diff --git a/drivers/usb/dwc3/ulpi.c b/drivers/usb/dwc3/ulpi.c
index e6e6176386a4..20f5d9aba317 100644
--- a/drivers/usb/dwc3/ulpi.c
+++ b/drivers/usb/dwc3/ulpi.c
@@ -24,7 +24,7 @@ static int dwc3_ulpi_busyloop(struct dwc3 *dwc)
 
 	while (count--) {
 		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYACC(0));
-		if (!(reg & DWC3_GUSB2PHYACC_BUSY))
+		if (reg & DWC3_GUSB2PHYACC_DONE)
 			return 0;
 		cpu_relax();
 	}
-- 
2.28.0