media: cadence: cdns-csi2rx: Support multiple pixels per clock cycle

The output pixel interface is a parallel bus (32 bits), which
supports sending multiple pixels (1, 2 or 4) per clock cycle for
smaller pixel widths like RAW8-RAW16.

Dual-pixel and Quad-pixel modes can be a requirement if the export rate
of the Cadence IP in Single-pixel mode maxes out before the maximum
supported DPHY-RX frequency, which is the case with TI's integration of
this IP [1].

So, we export a function that lets the downstream hardware block request
a higher pixel-per-clock on a particular output pad.

We check if we can support the requested pixels per clock given the
known maximum for the currently configured format. If not, we set it
to the highest feasible value and return this value to the caller.

[1] Section 12.6.1.4.8.14 CSI_RX_IF Programming Restrictions of AM62 TRM

Link: https://www.ti.com/lit/pdf/spruj16
Tested-by: Yemike Abhilash Chandra <[e-mail]> (on SK-AM68)
Signed-off-by: Jai Luthra <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

MAINTAINERS

···
 F:	Documentation/devicetree/bindings/media/cdns,*.txt
 F:	Documentation/devicetree/bindings/media/cdns,csi2rx.yaml
 F:	drivers/media/platform/cadence/cdns-csi2*
+F:	include/media/cadence/cdns-csi2*
 
 CADENCE NAND DRIVER
 L:	[e-mail]

drivers/media/platform/cadence/cdns-csi2rx.c

···
  * Copyright (C) 2017 Cadence Design Systems Inc.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/export.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
···
 #include <linux/reset.h>
 #include <linux/slab.h>
 
+#include <media/cadence/cdns-csi2rx.h>
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-fwnode.h>
···
 #define CSI2RX_STREAM_DATA_CFG_VC_SELECT(n)		BIT((n) + 16)
 
 #define CSI2RX_STREAM_CFG_REG(n)		(CSI2RX_STREAM_BASE(n) + 0x00c)
-#define CSI2RX_STREAM_CFG_FIFO_MODE_LARGE_BUF		(1 << 8)
+#define CSI2RX_STREAM_CFG_FIFO_MODE_LARGE_BUF		BIT(8)
+#define CSI2RX_STREAM_CFG_NUM_PIXELS_MASK		GENMASK(5, 4)
+#define CSI2RX_STREAM_CFG_NUM_PIXELS(n)			((n) >> 1U)
 
 #define CSI2RX_LANES_MAX	4
 #define CSI2RX_STREAMS_MAX	4
···
 
 struct csi2rx_fmt {
 	u32				code;
+	/* width of a single pixel on CSI-2 bus */
 	u8				bpp;
+	/* max pixels per clock supported on output bus */
+	u8				max_pixels;
 };
 
 struct csi2rx_event {
···
 	struct reset_control		*pixel_rst[CSI2RX_STREAMS_MAX];
 	struct phy			*dphy;
 
+	u8				num_pixels[CSI2RX_STREAMS_MAX];
 	u8				lanes[CSI2RX_LANES_MAX];
 	u8				num_lanes;
 	u8				max_lanes;
···
 };
 
 static const struct csi2rx_fmt formats[] = {
-	{ .code	= MEDIA_BUS_FMT_YUYV8_1X16, .bpp = 16, },
-	{ .code	= MEDIA_BUS_FMT_UYVY8_1X16, .bpp = 16, },
-	{ .code	= MEDIA_BUS_FMT_YVYU8_1X16, .bpp = 16, },
-	{ .code	= MEDIA_BUS_FMT_VYUY8_1X16, .bpp = 16, },
-	{ .code	= MEDIA_BUS_FMT_SBGGR8_1X8, .bpp = 8, },
-	{ .code	= MEDIA_BUS_FMT_SGBRG8_1X8, .bpp = 8, },
-	{ .code	= MEDIA_BUS_FMT_SGRBG8_1X8, .bpp = 8, },
-	{ .code	= MEDIA_BUS_FMT_SRGGB8_1X8, .bpp = 8, },
-	{ .code	= MEDIA_BUS_FMT_Y8_1X8,     .bpp = 8, },
-	{ .code	= MEDIA_BUS_FMT_SBGGR10_1X10, .bpp = 10, },
-	{ .code	= MEDIA_BUS_FMT_SGBRG10_1X10, .bpp = 10, },
-	{ .code	= MEDIA_BUS_FMT_SGRBG10_1X10, .bpp = 10, },
-	{ .code	= MEDIA_BUS_FMT_SRGGB10_1X10, .bpp = 10, },
-	{ .code	= MEDIA_BUS_FMT_RGB565_1X16,  .bpp = 16, },
-	{ .code	= MEDIA_BUS_FMT_RGB888_1X24,  .bpp = 24, },
-	{ .code	= MEDIA_BUS_FMT_BGR888_1X24,  .bpp = 24, },
+	{ .code	= MEDIA_BUS_FMT_YUYV8_1X16, .bpp = 16, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_UYVY8_1X16, .bpp = 16, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_YVYU8_1X16, .bpp = 16, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_VYUY8_1X16, .bpp = 16, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_SBGGR8_1X8, .bpp = 8, .max_pixels = 4, },
+	{ .code	= MEDIA_BUS_FMT_SGBRG8_1X8, .bpp = 8, .max_pixels = 4, },
+	{ .code	= MEDIA_BUS_FMT_SGRBG8_1X8, .bpp = 8, .max_pixels = 4, },
+	{ .code	= MEDIA_BUS_FMT_SRGGB8_1X8, .bpp = 8, .max_pixels = 4, },
+	{ .code	= MEDIA_BUS_FMT_Y8_1X8,     .bpp = 8, .max_pixels = 4, },
+	{ .code	= MEDIA_BUS_FMT_SBGGR10_1X10, .bpp = 10, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_SGBRG10_1X10, .bpp = 10, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_SGRBG10_1X10, .bpp = 10, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_SRGGB10_1X10, .bpp = 10, .max_pixels = 2, },
+	{ .code	= MEDIA_BUS_FMT_RGB565_1X16,  .bpp = 16, .max_pixels = 1, },
+	{ .code	= MEDIA_BUS_FMT_RGB888_1X24,  .bpp = 24, .max_pixels = 1, },
+	{ .code	= MEDIA_BUS_FMT_BGR888_1X24,  .bpp = 24, .max_pixels = 1, },
 };
 
 static void csi2rx_configure_error_irq_mask(void __iomem *base,
···
 
 		reset_control_deassert(csi2rx->pixel_rst[i]);
 
-		writel(CSI2RX_STREAM_CFG_FIFO_MODE_LARGE_BUF,
+		writel(CSI2RX_STREAM_CFG_FIFO_MODE_LARGE_BUF |
+			       FIELD_PREP(CSI2RX_STREAM_CFG_NUM_PIXELS_MASK,
+					  csi2rx->num_pixels[i]),
 		       csi2rx->base + CSI2RX_STREAM_CFG_REG(i));
 
 		/*
···
 
 	return csi2rx_set_fmt(subdev, state, &format);
 }
+
+int cdns_csi2rx_negotiate_ppc(struct v4l2_subdev *subdev, unsigned int pad,
+			      u8 *ppc)
+{
+	struct csi2rx_priv *csi2rx = v4l2_subdev_to_csi2rx(subdev);
+	const struct csi2rx_fmt *csi_fmt;
+	struct v4l2_subdev_state *state;
+	struct v4l2_mbus_framefmt *fmt;
+
+	if (!ppc || pad < CSI2RX_PAD_SOURCE_STREAM0 || pad >= CSI2RX_PAD_MAX)
+		return -EINVAL;
+
+	state = v4l2_subdev_lock_and_get_active_state(subdev);
+	fmt = v4l2_subdev_state_get_format(state, pad);
+	csi_fmt = csi2rx_get_fmt_by_code(fmt->code);
+
+	/* Reduce requested PPC if it is too high */
+	*ppc = min(*ppc, csi_fmt->max_pixels);
+
+	v4l2_subdev_unlock_state(state);
+
+	csi2rx->num_pixels[pad - CSI2RX_PAD_SOURCE_STREAM0] =
+		CSI2RX_STREAM_CFG_NUM_PIXELS(*ppc);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL_FOR_MODULES(cdns_csi2rx_negotiate_ppc, "j721e-csi2rx");
 
 static const struct v4l2_subdev_pad_ops csi2rx_pad_ops = {
 	.enum_mbus_code	= csi2rx_enum_mbus_code,

include/media/cadence/cdns-csi2rx.h

···
+/* SPDX-License-Identifier: GPL-2.0+ */
+#ifndef _CDNS_CSI2RX_H
+#define _CDNS_CSI2RX_H
+
+#include <media/v4l2-subdev.h>
+
+/**
+ * cdns_csi2rx_negotiate_ppc - Negotiate pixel-per-clock on output interface
+ *
+ * @subdev: point to &struct v4l2_subdev
+ * @pad: pad number of the source pad
+ * @ppc: pointer to requested pixel-per-clock value
+ *
+ * Returns 0 on success, negative error code otherwise.
+ */
+int cdns_csi2rx_negotiate_ppc(struct v4l2_subdev *subdev, unsigned int pad,
+			      u8 *ppc);
+
+#endif