linux-kernel - [PATCH 2/2] usb: dwc3: Program USB Gen2 De-emphasis defined in PIPE4 spec

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Message-ID: <20241007135508.3143756-5-joychakr@google.com>
Date: Mon,  7 Oct 2024 13:55:08 +0000
From: Joy Chakraborty <joychakr@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Felipe Balbi <balbi@...nel.org>
Cc: linux-usb@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Joy Chakraborty <joychakr@...gle.com>
Subject: [PATCH 2/2] usb: dwc3: Program USB Gen2 De-emphasis defined in PIPE4 spec

Set 18bit TxDeemph[17:0] in LCSR_TX_DEEMPH(n) register for USB3 Gen2
Normal Operation as defined in PIPE4 spec based on dt quirk
"snps,tx_gen2_de_emphasis_quirk" and "snps,tx_gen2_de_emphasis".

Signed-off-by: Joy Chakraborty <joychakr@...gle.com>
---
 drivers/usb/dwc3/core.c | 13 +++++++++++++
 drivers/usb/dwc3/core.h |  6 ++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9eb085f359ce..25e19aea364a 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -693,6 +693,11 @@ static int dwc3_ss_phy_setup(struct dwc3 *dwc, int index)
 
 	dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(index), reg);
 
+	if (dwc->tx_gen2_de_emphasis_quirk) {
+		reg = dwc->tx_gen2_de_emphasis;
+		dwc3_writel(dwc->regs, DWC3_LCSR_TX_DEEMPH(index), reg);
+	}
+
 	return 0;
 }
 
@@ -1654,6 +1659,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	u8			tx_thr_num_pkt_prd = 0;
 	u8			tx_max_burst_prd = 0;
 	u8			tx_fifo_resize_max_num;
+	u32			tx_gen2_de_emphasis = 0;
 	const char		*usb_psy_name;
 	int			ret;
 
@@ -1797,8 +1803,15 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	dwc->dis_split_quirk = device_property_read_bool(dev,
 				"snps,dis-split-quirk");
 
+	dwc->tx_gen2_de_emphasis_quirk = device_property_read_bool(dev,
+								   "snps,tx_gen2_de_emphasis_quirk");
+	if (dwc->tx_gen2_de_emphasis_quirk)
+		device_property_read_u32(dev, "snps,tx_gen2_de_emphasis",
+					 &tx_gen2_de_emphasis);
+
 	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
 	dwc->tx_de_emphasis = tx_de_emphasis;
+	dwc->tx_gen2_de_emphasis = tx_gen2_de_emphasis;
 
 	dwc->hird_threshold = hird_threshold;
 
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index c71240e8f7c7..fa9db38b7e15 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -179,7 +179,9 @@
 #define DWC3_OEVTEN		0xcc0C
 #define DWC3_OSTS		0xcc10
 
+/* Link Registers */
 #define DWC3_LLUCTL		0xd024
+#define DWC3_LCSR_TX_DEEMPH(n)	(0xd060 + ((n) * 0x80))
 
 /* Bit fields */
 
@@ -1145,6 +1147,8 @@ struct dwc3_scratchpad_array {
  *	1	- -3.5dB de-emphasis
  *	2	- No de-emphasis
  *	3	- Reserved
+ * @tx_gen2_de_emphasis_quirk: set if we enable USB Gen2 Tx de-emphasis quirk
+ * @tx_gen2_de_emphasis: Tx de-emphasis value used in USB Gen2 with PIPE4
  * @dis_metastability_quirk: set to disable metastability quirk.
  * @dis_split_quirk: set to disable split boundary.
  * @sys_wakeup: set if the device may do system wakeup.
@@ -1374,6 +1378,8 @@ struct dwc3 {
 
 	unsigned		tx_de_emphasis_quirk:1;
 	unsigned		tx_de_emphasis:2;
+	unsigned		tx_gen2_de_emphasis_quirk:1;
+	unsigned		tx_gen2_de_emphasis:18;
 
 	unsigned		dis_metastability_quirk:1;
 
-- 
2.47.0.rc0.187.ge670bccf7e-goog