linux-kernel - [PATCH v3] usb: dwc3: core: Add quirk for enabling AutoRetry feature in the controller

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Date:   Thu, 26 Jul 2018 18:38:48 +0530
From:   Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
To:     <balbi@...nel.org>, <gregkh@...uxfoundation.org>
CC:     <v.anuragkumar@...il.com>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
Subject: [PATCH v3] usb: dwc3: core: Add quirk for enabling AutoRetry feature in the controller

By default when core sees any transaction error(CRC or overflow)
it replies with terminating retry ACK (Retry=1 and Nump == 0).
Enabling this Auto Retry feature in controller, on seeing any
transaction errors makes the core to send a non-terminating ACK
transaction packet (that is, ACK TP with Retry=1 and Nump != 0).
Doing so will give controller a chance to recover from the error
condition.

Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
---
 Changes in v3:
	1. As suggested by Felipe, added OTG related check
	2. Corrected the multi-line commenting format

 Changes in v2:
	1. As suggested by Rob Herring & Felipe Balbi removed the
	   quirk logic and setting the AutoRetry bits unconditionally
	   for hostmode
---
 drivers/usb/dwc3/core.c | 16 ++++++++++++++++
 drivers/usb/dwc3/core.h |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1038075..bc9e33c 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -883,6 +883,22 @@ static int dwc3_core_init(struct dwc3 *dwc)
 		dwc3_writel(dwc->regs, DWC3_GUCTL1, reg);
 	}
 
+	if (dwc->dr_mode == USB_DR_MODE_HOST ||
+	    dwc->dr_mode == USB_DR_MODE_OTG) {
+		reg = dwc3_readl(dwc->regs, DWC3_GUCTL);
+
+		/*
+		 * Enable Auto retry Feature to make the controller operating in
+		 * Host mode on seeing transaction errors(CRC errors or internal
+		 * overrun scenerios) on IN transfers to reply to the device
+		 * with a non-terminating retry ACK (i.e, an ACK transcation
+		 * packet with Retry=1 & Nump != 0)
+		 */
+		reg |= DWC3_GUCTL_HSTINAUTORETRY;
+
+		dwc3_writel(dwc->regs, DWC3_GUCTL, reg);
+	}
+
 	/*
 	 * Must config both number of packets and max burst settings to enable
 	 * RX and/or TX threshold.
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 285ce0e..92a1077 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -227,6 +227,9 @@
 #define DWC3_GCTL_GBLHIBERNATIONEN	BIT(1)
 #define DWC3_GCTL_DSBLCLKGTNG		BIT(0)
 
+/* Global User Control Register */
+#define DWC3_GUCTL_HSTINAUTORETRY	BIT(14)
+
 /* Global User Control 1 Register */
 #define DWC3_GUCTL1_TX_IPGAP_LINECHECK_DIS	BIT(28)
 #define DWC3_GUCTL1_DEV_L1_EXIT_BY_HW	BIT(24)
-- 
2.1.1