Re: [PATCH v4 2/6] phy: cdns-dphy: Add Rx support

quoted

Hi Laurent,

Thanks for reviewing.

On 23/08/21 04:37AM, Laurent Pinchart wrote:
Hi Pratyush,

Thank you for the patch.

On Sat, Aug 21, 2021 at 12:33:42AM +0530, Pratyush Yadav wrote:
The Cadence DPHY can be used to receive image data over the CSI-2
protocol. Add support for Rx mode. The programming sequence differs from
the Tx mode so it is added as a separate set of hooks to isolate the two
paths. The mode in which the DPHY has to be used is selected based on
the compatible.

Signed-off-by: Pratyush Yadav <redacted>

---

Changes in v4:
- Drop the submode parts. Use a different compatible for the Rx ops.
- Make bands and num_bands static.

Changes in v3:
- Use a table to select the band.
- Use a table to poll the data lane ready bits.
- Multiply the DPHY HS clock rate by 2 to get the bit rate since the
  clock is DDR.

 drivers/phy/cadence/cdns-dphy.c | 171 ++++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)

diff --git a/drivers/phy/cadence/cdns-dphy.c b/drivers/phy/cadence/cdns-dphy.c
index 0a169d649216..149fccdfad38 100644
--- a/drivers/phy/cadence/cdns-dphy.c
+++ b/drivers/phy/cadence/cdns-dphy.c
@@ -1,11 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright: 2017-2018 Cadence Design Systems, Inc.
+ * Copyright (C) 2021 Texas Instruments Incorporated - https://www.ti.com/
  */
 
 #include <linux/bitops.h>
+#include <linux/bitfield.h>
Alphabetical order please.

 #include <linux/clk.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>
@@ -25,10 +28,14 @@
 #define DPHY_PMA_RCLK(reg)		(0x600 + (reg))
 #define DPHY_PMA_RDATA(lane, reg)	(0x700 + ((lane) * 0x100) + (reg))
 #define DPHY_PCS(reg)			(0xb00 + (reg))
+#define DPHY_ISO(reg)			(0xc00 + (reg))
 
 #define DPHY_CMN_SSM			DPHY_PMA_CMN(0x20)
 #define DPHY_CMN_SSM_EN			BIT(0)
+#define DPHY_CMN_RX_BANDGAP_TIMER_MASK	GENMASK(8, 1)
 #define DPHY_CMN_TX_MODE_EN		BIT(9)
+#define DPHY_CMN_RX_MODE_EN		BIT(10)
+#define DPHY_CMN_RX_BANDGAP_TIMER	0x14
 
 #define DPHY_CMN_PWM			DPHY_PMA_CMN(0x40)
 #define DPHY_CMN_PWM_DIV(x)		((x) << 20)
@@ -45,10 +52,27 @@
 #define DPHY_CMN_OPDIV_FROM_REG		BIT(6)
 #define DPHY_CMN_OPDIV(x)		((x) << 7)
 
+#define DPHY_BAND_CFG			DPHY_PCS(0x0)
+#define DPHY_BAND_CFG_LEFT_BAND		GENMASK(4, 0)
+#define DPHY_BAND_CFG_RIGHT_BAND	GENMASK(9, 5)
+
 #define DPHY_PSM_CFG			DPHY_PCS(0x4)
 #define DPHY_PSM_CFG_FROM_REG		BIT(0)
 #define DPHY_PSM_CLK_DIV(x)		((x) << 1)
 
+#define DPHY_POWER_ISLAND_EN_DATA	DPHY_PCS(0x8)
+#define DPHY_POWER_ISLAND_EN_DATA_VAL	0xaaaaaaaa
+#define DPHY_POWER_ISLAND_EN_CLK	DPHY_PCS(0xc)
+#define DPHY_POWER_ISLAND_EN_CLK_VAL	0xaa
+
+#define DPHY_ISO_CL_CTRL_L		DPHY_ISO(0x10)
+#define DPHY_ISO_DL_CTRL_L0		DPHY_ISO(0x14)
+#define DPHY_ISO_DL_CTRL_L1		DPHY_ISO(0x20)
+#define DPHY_ISO_DL_CTRL_L2		DPHY_ISO(0x30)
+#define DPHY_ISO_DL_CTRL_L3		DPHY_ISO(0x3c)
+#define DPHY_ISO_LANE_READY_BIT		0
+#define DPHY_ISO_LANE_READY_TIMEOUT_MS	100UL
+
 #define DSI_HBP_FRAME_OVERHEAD		12
 #define DSI_HSA_FRAME_OVERHEAD		14
 #define DSI_HFP_FRAME_OVERHEAD		6
@@ -57,6 +81,9 @@
 #define DSI_NULL_FRAME_OVERHEAD		6
 #define DSI_EOT_PKT_SIZE		4
 
+#define DPHY_LANES_MIN			1
+#define DPHY_LANES_MAX			4
+
 struct cdns_dphy_cfg {
 	u8 pll_ipdiv;
 	u8 pll_opdiv;
@@ -98,6 +125,22 @@ struct cdns_dphy {
 	struct phy *phy;
 };
 
+struct cdns_dphy_rx_band {
+	unsigned int min_rate;
+	unsigned int max_rate;
+};
+
+/* Order of bands is important since the index is the band number. */
+static struct cdns_dphy_rx_band bands[] = {
static const

+	{80, 100}, {100, 120}, {120, 160}, {160, 200}, {200, 240},
+	{240, 280}, {280, 320}, {320, 360}, {360, 400}, {400, 480},
+	{480, 560}, {560, 640}, {640, 720}, {720, 800}, {800, 880},
+	{880, 1040}, {1040, 1200}, {1200, 1350}, {1350, 1500}, {1500, 1750},
+	{1750, 2000}, {2000, 2250}, {2250, 2500}
+};
+
+static int num_bands = ARRAY_SIZE(bands);
No need for a variable (which should be const otherwise), you can use
ARRAY_SIZE(bands) where needed.

+
 static int cdns_dsi_get_dphy_pll_cfg(struct cdns_dphy *dphy,
 				     struct cdns_dphy_cfg *cfg,
 				     struct phy_configure_opts_mipi_dphy *opts,
@@ -309,6 +352,132 @@ static const struct cdns_dphy_ops tx_ref_dphy_ops = {
 	.set_psm_div = cdns_dphy_ref_set_psm_div,
 };
 
+static int cdns_dphy_rx_power_on(struct cdns_dphy *dphy)
+{
+	/* Start RX state machine. */
+	writel(DPHY_CMN_SSM_EN | DPHY_CMN_RX_MODE_EN |
+	       FIELD_PREP(DPHY_CMN_RX_BANDGAP_TIMER_MASK,
+			  DPHY_CMN_RX_BANDGAP_TIMER),
+	       dphy->regs + DPHY_CMN_SSM);
+
+	return 0;
+}
+
+static int cdns_dphy_rx_power_off(struct cdns_dphy *dphy)
+{
+	writel(0, dphy->regs + DPHY_CMN_SSM);
+
+	return 0;
+}
+
+static int cdns_dphy_rx_get_band_ctrl(unsigned long hs_clk_rate)
+{
+	unsigned int rate;
+	int i;
i is never negative, you can make it an unsigned int.

+
+	rate = hs_clk_rate / 1000000UL;
+	/* Since CSI-2 clock is DDR, the bit rate is twice the clock rate. */
+	rate *= 2;
+
+	if (rate < bands[0].min_rate || rate >= bands[num_bands - 1].max_rate)
+		return -EOPNOTSUPP;
+
+	for (i = 0; i < num_bands; i++) {
+		if (rate >= bands[i].min_rate && rate < bands[i].max_rate)
You can replace this with

		if (rate < bands[i].max_rate)

as the bands are in increasing order.

+			return i;
+	}
+
+	/* Unreachable. */
+	WARN(1, "Reached unreachable code.");
+	return -EINVAL;
That's not very nice.

As a clock rate higher than the maximum isn't supposed to happen, you
could drop that initial check (it won't affect performance) and return
-EOPNOTSUPP here without a WARN().
Ok.


+}
+
+static int cdns_dphy_rx_wait_for_bit(void __iomem *addr, unsigned int bit)
+{
+	u32 val;
+
+	return readl_relaxed_poll_timeout(addr, val, val & BIT(bit), 10,
+					  DPHY_ISO_LANE_READY_TIMEOUT_MS * 1000);
A busy wait for one second is quite long. How long does it typically
take for the condition to be true ?
I have not measured. I don't see any timing information in the 
datasheet.

But the timeout is 100 miliseconds not 1 second. 
readl_relaxed_poll_timeout() expects microseconds, so we multiply by 
1000. The value of DPHY_ISO_LANE_READY_TIMEOUT_MS is 100, so it will be 
a 100 ms timeout, which I think is reasonable.


+}
+
+static int cdns_dphy_rx_wait_lane_ready(struct cdns_dphy *dphy, int lanes)
lanes should be an unsigned int.

+{
+	void __iomem *reg = dphy->regs;
You can use dphy->regs directly in the code below.

+	u32 data_lane_ctrl[] = {DPHY_ISO_DL_CTRL_L0, DPHY_ISO_DL_CTRL_L1,
+				DPHY_ISO_DL_CTRL_L2, DPHY_ISO_DL_CTRL_L3};
static const, and move it first in the function.
Ok. But out of curiosity, why?


+	int ret, i;
i is never negative here either.
Yes. Will change to unsigned.


+
+	/* Data lanes. Minimum one lane is mandatory. */
+	if (lanes < DPHY_LANES_MIN || lanes > DPHY_LANES_MAX)
+		return -EINVAL;
+
+	/* Clock lane */
+	ret = cdns_dphy_rx_wait_for_bit(reg + DPHY_ISO_CL_CTRL_L,
+					DPHY_ISO_LANE_READY_BIT);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < lanes; i++) {
+		ret = cdns_dphy_rx_wait_for_bit(reg + data_lane_ctrl[i],
+						DPHY_ISO_LANE_READY_BIT);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int cdns_dphy_rx_configure(struct cdns_dphy *dphy,
+				  union phy_configure_opts *opts)
+{
+	unsigned int reg;
+	int band_ctrl, ret;
+
+	band_ctrl = cdns_dphy_rx_get_band_ctrl(opts->mipi_dphy.hs_clk_rate);
+	if (band_ctrl < 0)
+		return band_ctrl;
+
+	reg = FIELD_PREP(DPHY_BAND_CFG_LEFT_BAND, band_ctrl) |
+	      FIELD_PREP(DPHY_BAND_CFG_RIGHT_BAND, band_ctrl);
+	writel(reg, dphy->regs + DPHY_BAND_CFG);
+
+	/*
+	 * Set the required power island phase 2 time. This is mandated by DPHY
+	 * specs.
+	 */
+	reg = DPHY_POWER_ISLAND_EN_DATA_VAL;
+	writel(reg, dphy->regs + DPHY_POWER_ISLAND_EN_DATA);
+	reg = DPHY_POWER_ISLAND_EN_CLK_VAL;
+	writel(reg, dphy->regs + DPHY_POWER_ISLAND_EN_CLK);
+
+	ret = cdns_dphy_rx_wait_lane_ready(dphy, opts->mipi_dphy.lanes);
+	if (ret) {
+		dev_err(dphy->dev, "DPHY wait for lane ready timeout\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int cdns_dphy_rx_validate(struct cdns_dphy *dphy, enum phy_mode mode,
+				 int submode, union phy_configure_opts *opts)
+{
+	int ret;
+
+	ret = cdns_dphy_rx_get_band_ctrl(opts->mipi_dphy.hs_clk_rate);
+	if (ret < 0)
+		return ret;
+
+	return phy_mipi_dphy_config_validate(&opts->mipi_dphy);
+}
+
+static const struct cdns_dphy_ops rx_ref_dphy_ops = {
+	.power_on = cdns_dphy_rx_power_on,
+	.power_off = cdns_dphy_rx_power_off,
+	.configure = cdns_dphy_rx_configure,
+	.validate = cdns_dphy_rx_validate,
+};
+
 static int cdns_dphy_validate(struct phy *phy, enum phy_mode mode, int submode,
 			      union phy_configure_opts *opts)
 {
@@ -421,6 +590,7 @@ static int cdns_dphy_remove(struct platform_device *pdev)
 
 static const struct of_device_id cdns_dphy_of_match[] = {
 	{ .compatible = "cdns,dphy", .data = &tx_ref_dphy_ops },
+	{ .compatible = "cdns,dphy-rx", .data = &rx_ref_dphy_ops },
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, cdns_dphy_of_match);
@@ -436,5 +606,6 @@ static struct platform_driver cdns_dphy_platform_driver = {
 module_platform_driver(cdns_dphy_platform_driver);
 
 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@bootlin.com>");
+MODULE_AUTHOR("Pratyush Yadav <p.yadav@ti.com>");
 MODULE_DESCRIPTION("Cadence MIPI D-PHY Driver");
 MODULE_LICENSE("GPL");
-- 
Regards,

Laurent Pinchart
-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

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