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Date:   Sun, 24 May 2020 06:08:13 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Venkateshwar Rao Gannavarapu 
        <venkateshwar.rao.gannavarapu@xilinx.com>
Cc:     Hyun Kwon <hyun.kwon@xilinx.com>, Hyun Kwon <hyunk@xilinx.com>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "airlied@linux.ie" <airlied@linux.ie>,
        "daniel@ffwll.ch" <daniel@ffwll.ch>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sandip Kothari <sandipk@xilinx.com>,
        Venkateshwar Rao Gannavarapu <VGANNAVA@xilinx.com>
Subject: Re: [RFC PATCH 2/2] drm: xlnx: driver for Xilinx DSI TX Subsystem
Message-ID: <20200524030813.GF6026@pendragon.ideasonboard.com>
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 <20200504184348.GA3095@smtp.xilinx.com>
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Hi GVRao,

Thank you for the patch.

On Mon, May 04, 2020 at 11:43:48AM -0700, Hyun Kwon wrote:
> On Mon, 2020-04-20 at 14:20:56 -0700, Venkateshwar Rao Gannavarapu wrote:
> > The Xilinx MIPI DSI Tx Subsystem soft IP is used to display video
> > data from AXI-4 stream interface.
> > 
> > It supports upto 4 lanes, optional register interface for the DPHY,
> 
> I don't see the register interface for dphy support.

I think the D-PHY should be supported through a PHY driver, as it seems
to be shared between different subsystems.

> > multiple RGB color formats, command mode and video mode.
> > This is a MIPI-DSI host driver and provides DSI bus for panels.
> > This driver also helps to communicate with its panel using panel
> > framework.
> > 
> > Signed-off-by: Venkateshwar Rao Gannavarapu <venkateshwar.rao.gannavarapu@xilinx.com>
> > ---
> >  drivers/gpu/drm/xlnx/Kconfig    |  11 +
> >  drivers/gpu/drm/xlnx/Makefile   |   2 +
> >  drivers/gpu/drm/xlnx/xlnx_dsi.c | 755 ++++++++++++++++++++++++++++++++++++++++

Daniel Vetter has recently expressed his opiion that bridge drivers
should go to drivers/gpu/drm/bridge/. It would then be
drivers/gpu/drm/bridge/xlnx/. I don't have a strong opinion myself.

> >  3 files changed, 768 insertions(+)
> >  create mode 100644 drivers/gpu/drm/xlnx/xlnx_dsi.c
> > 
> > diff --git a/drivers/gpu/drm/xlnx/Kconfig b/drivers/gpu/drm/xlnx/Kconfig
> > index aa6cd88..73873cf 100644
> > --- a/drivers/gpu/drm/xlnx/Kconfig
> > +++ b/drivers/gpu/drm/xlnx/Kconfig
> > @@ -11,3 +11,14 @@ config DRM_ZYNQMP_DPSUB
> >  	  This is a DRM/KMS driver for ZynqMP DisplayPort controller. Choose
> >  	  this option if you have a Xilinx ZynqMP SoC with DisplayPort
> >  	  subsystem.
> > +
> > +config DRM_XLNX_DSI
> > +        tristate "Xilinx DRM DSI Subsystem Driver"
> > +        select DRM_MIPI_DSI
> > +        select DRM_PANEL
> > +        select DRM_PANEL_SIMPLE
> > +        help
> > +	  This enables support for Xilinx MIPI-DSI.
> 
> This sentence is not needed with below. Could you please rephrase the whole?
> 
> > +	  This is a DRM/KMS driver for Xilinx programmable DSI controller.
> > +	  Choose this option if you have a Xilinx MIPI DSI-TX controller
> > +	  subsytem.
> 
> These seem incorrectly indented.
> 
> > diff --git a/drivers/gpu/drm/xlnx/Makefile b/drivers/gpu/drm/xlnx/Makefile
> > index 2b844c6..b7ee6ef 100644
> > --- a/drivers/gpu/drm/xlnx/Makefile
> > +++ b/drivers/gpu/drm/xlnx/Makefile
> > @@ -1,2 +1,4 @@
> >  zynqmp-dpsub-objs += zynqmp_disp.o zynqmp_dpsub.o zynqmp_dp.o
> >  obj-$(CONFIG_DRM_ZYNQMP_DPSUB) += zynqmp-dpsub.o
> > +
> > +obj-$(CONFIG_DRM_XLNX_DSI) += xlnx_dsi.o
> > diff --git a/drivers/gpu/drm/xlnx/xlnx_dsi.c b/drivers/gpu/drm/xlnx/xlnx_dsi.c
> > new file mode 100644
> > index 0000000..b8cae59
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xlnx/xlnx_dsi.c
> > @@ -0,0 +1,755 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Xilinx FPGA MIPI DSI Tx Controller driver
> > + *
> > + * Copyright (C) 2017 - 2019 Xilinx, Inc.
> > + *
> > + * Authors:
> > + * - Saurabh Sengar <saurabhs@xilinx.com>
> > + * - Venkateshwar Rao Gannavarapu <venkateshwar.rao.gannavarapu@xilinx.com>
> > + */
> > +
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_connector.h>
> > +#include <drm/drm_crtc.h>
> > +#include <drm/drm_crtc_helper.h>
> > +#include <drm/drm_device.h>
> > +#include <drm/drm_encoder.h>
> > +#include <drm/drm_fourcc.h>
> > +#include <drm/drm_gem_cma_helper.h>
> > +#include <drm/drm_mipi_dsi.h>
> > +#include <drm/drm_panel.h>
> > +#include <drm/drm_probe_helper.h>
> > +
> > +#include <linux/clk.h>
> > +#include <linux/component.h>
> > +#include <linux/device.h>
> > +#include <linux/iopoll.h>
> > +#include <linux/of_device.h>
> > +#include <linux/of_graph.h>
> > +#include <linux/phy/phy.h>
> > +
> > +#include <video/mipi_display.h>
> > +#include <video/videomode.h>
> > +
> > +/* DSI Tx IP registers */
> > +#define XDSI_CCR			0x00
> > +#define XDSI_CCR_COREENB		BIT(0)
> > +#define XDSI_CCR_SOFTRST		BIT(1)
> > +#define XDSI_CCR_CRREADY		BIT(2)
> > +#define XDSI_CCR_CMDMODE		BIT(3)
> > +#define XDSI_CCR_DFIFORST		BIT(4)
> > +#define XDSI_CCR_CMDFIFORST		BIT(5)
> > +#define XDSI_PCR			0x04
> > +#define XDSI_PCR_VIDEOMODE(x)		(((x) & 0x3) << 3)
> > +#define XDSI_PCR_VIDEOMODE_MASK		(0x3 << 3)
> > +#define XDSI_PCR_VIDEOMODE_SHIFT	3
> > +#define XDSI_PCR_BLLPTYPE(x)		((x) << 5)
> > +#define XDSI_PCR_BLLPMODE(x)		((x) << 6)
> > +#define XDSI_PCR_EOTPENABLE(x)		((x) << 13)
> > +#define XDSI_GIER			0x20
> > +#define XDSI_ISR			0x24
> > +#define XDSI_IER			0x28
> > +#define XDSI_STR			0x2C
> > +#define XDSI_STR_RDY_SHPKT		BIT(6)
> > +#define XDSI_STR_RDY_LNGPKT		BIT(7)
> > +#define XDSI_STR_DFIFO_FULL		BIT(8)
> > +#define XDSI_STR_DFIFO_EMPTY		BIT(9)
> > +#define XDSI_STR_WAITFR_DATA		BIT(10)
> > +#define XDSI_STR_CMD_EXE_PGS		BIT(11)
> > +#define XDSI_STR_CCMD_PROC		BIT(12)
> > +#define XDSI_STR_LPKT_MASK		(0x5 << 7)
> > +#define XDSI_CMD			0x30
> > +#define XDSI_CMD_QUEUE_PACKET(x)	((x) & GENMASK(23, 0))
> > +#define XDSI_DFR			0x34
> > +#define XDSI_TIME1			0x50
> > +#define XDSI_TIME1_BLLP_BURST(x)	((x) & GENMASK(15, 0))
> > +#define XDSI_TIME1_HSA(x)		(((x) & GENMASK(15, 0)) << 16)
> > +#define XDSI_TIME2			0x54
> > +#define XDSI_TIME2_VACT(x)		((x) & GENMASK(15, 0))
> > +#define XDSI_TIME2_HACT(x)		(((x) & GENMASK(15, 0)) << 16)
> > +#define XDSI_HACT_MULTIPLIER		GENMASK(1, 0)
> > +#define XDSI_TIME3			0x58
> > +#define XDSI_TIME3_HFP(x)		((x) & GENMASK(15, 0))
> > +#define XDSI_TIME3_HBP(x)		(((x) & GENMASK(15, 0)) << 16)
> > +#define XDSI_TIME4			0x5c
> > +#define XDSI_TIME4_VFP(x)		((x) & GENMASK(7, 0))
> > +#define XDSI_TIME4_VBP(x)		(((x) & GENMASK(7, 0)) << 8)
> > +#define XDSI_TIME4_VSA(x)		(((x) & GENMASK(7, 0)) << 16)
> > +#define XDSI_LTIME			0x60
> > +#define XDSI_BLLP_TIME			0x64
> > +/*
> > + * XDSI_NUM_DATA_T represents number of data types in the
> > + * enum mipi_dsi_pixel_format in the MIPI DSI part of DRM framework.
> > + */
> > +#define XDSI_NUM_DATA_T			4
> > +#define XDSI_VIDEO_MODE_SYNC_PULSE	0x0
> > +#define XDSI_VIDEO_MODE_SYNC_EVENT	0x1
> > +#define XDSI_VIDEO_MODE_BURST		0x2
> 
> Please remove these unused 3 definitions.
> 
> > +
> > +#define XDSI_DPHY_CLK_MIN	197000000000UL
> > +#define XDSI_DPHY_CLK_MAX	203000000000UL
> > +#define XDSI_DPHY_CLK_REQ	200000000000UL
> > +
> > +/* command timeout in usec */
> > +#define XDSI_CMD_TIMEOUT_VAL	(3000)
> > +
> > +/**
> > + * struct xlnx_dsi - Xilinx DSI-TX core
> > + * @encoder: DRM encoder structure
> > + * @dsi_host: DSI host device
> > + * @connector: DRM connector structure
> > + * @panel_node: MIPI DSI device panel node
> > + * @panel:  DRM panel structure
> > + * @dev: device structure
> > + * @iomem: Base address of DSI subsystem
> > + * @lanes: number of active data lanes supported by DSI controller
> > + * @cmdmode: command mode support
> > + * @mode_flags: DSI operation mode related flags
> > + * @format: pixel format for video mode of DSI controller
> > + * @vm: videomode data structure
> > + * @mul_factor: multiplication factor for HACT timing parameter
> > + * @video_aclk: Video clock
> > + * @dphy_clk_200M: 200MHz DPHY clock and AXI Lite clock
> > + */
> > +struct xlnx_dsi {
> > +	struct drm_encoder encoder;
> > +	struct mipi_dsi_host dsi_host;
> > +	struct drm_connector connector;
> > +	struct device_node *panel_node;
> > +	struct drm_panel *panel;
> > +	struct device *dev;
> > +	void __iomem *iomem;
> > +	u32 lanes;
> > +	bool cmdmode;
> > +	u32 mode_flags;
> > +	enum mipi_dsi_pixel_format format;
> > +	struct videomode vm;
> > +	u32 mul_factor;
> > +	struct clk *video_aclk;
> > +	struct clk *dphy_clk_200M;
> > +};
> > +
> > +#define host_to_dsi(host) container_of(host, struct xlnx_dsi, dsi_host)
> > +#define connector_to_dsi(c) container_of(c, struct xlnx_dsi, connector)
> > +#define encoder_to_dsi(e) container_of(e, struct xlnx_dsi, encoder)
> > +
> > +static inline void xlnx_dsi_writel(void __iomem *base, int offset, u32 val)
> > +{
> > +	writel(val, base + offset);
> > +}
> > +
> > +static inline u32 xlnx_dsi_readl(void __iomem *base, int offset)
> > +{
> > +	return readl(base + offset);
> > +}
> > +
> > +/**
> > + * xlnx_dsi_set_display_mode - Configure DSI timing registers
> > + * @dsi: xilinx DSI structure
> > + *
> > + * This function writes the timing parameters of DSI IP which are
> > + * retrieved from panel timing values.
> > + */
> > +static void xlnx_dsi_set_display_mode(struct xlnx_dsi *dsi)
> 
> This function better directly inline to xlnx_dsi_atomic_mode_set(). Then,
> the videomode is not really needed. Please remove it and use drm_display_mode.
> 
> > +{
> > +	struct videomode *vm = &dsi->vm;
> > +	u32 reg, video_mode;
> > +
> > +	reg = xlnx_dsi_readl(dsi->iomem, XDSI_PCR);
> > +	video_mode = (reg & XDSI_PCR_VIDEOMODE_MASK) >>
> > +		      XDSI_PCR_VIDEOMODE_SHIFT;
> > +
> > +	/* configure the HSA value only if non_burst_sync_pluse video mode */
> > +	if (!video_mode &&
> > +	    (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)) {
> > +		reg = XDSI_TIME1_HSA(vm->hsync_len);
> > +		xlnx_dsi_writel(dsi->iomem, XDSI_TIME1, reg);
> > +	}
> > +
> > +	reg = XDSI_TIME4_VFP(vm->vfront_porch) |
> > +	      XDSI_TIME4_VBP(vm->vback_porch) |
> > +	      XDSI_TIME4_VSA(vm->vsync_len);
> > +	xlnx_dsi_writel(dsi->iomem, XDSI_TIME4, reg);
> > +
> > +	reg = XDSI_TIME3_HFP(vm->hfront_porch) |
> > +	      XDSI_TIME3_HBP(vm->hback_porch);
> > +	xlnx_dsi_writel(dsi->iomem, XDSI_TIME3, reg);
> > +
> > +	dev_dbg(dsi->dev, "mul factor for parsed datatype is = %d\n",
> > +		(dsi->mul_factor) / 100);
> 
> Remove unneeded ().
> 
> > +	/*
> > +	 * The HACT parameter received from panel timing values should be
> > +	 * divisible by 4. The reason for this is, the word count given as
> > +	 * input to DSI controller is HACT * mul_factor. The mul_factor is
> > +	 * 3, 2.25, 2.25, 2 respectively for RGB888, RGB666_L, RGB666_P and
> > +	 * RGB565.
> > +	 * e.g. for RGB666_L color format and 1080p, the word count is
> > +	 * 1920*2.25 = 4320 which is divisible by 4 and it is a valid input
> > +	 * to DSI controller. Based on this 2.25 mul factor, we come up with
> > +	 * the division factor of (XDSI_HACT_MULTIPLIER) as 4 for checking
> > +	 */
> > +	if ((vm->hactive & XDSI_HACT_MULTIPLIER) != 0)
> 
> if (!(vm->hactive & XDSI_HACT_MULTIPLIER))?
> 
> > +		dev_warn(dsi->dev, "Incorrect HACT will be programmed\n");
> 
> dev_warn() better come with more details. Probably it can mention that
> hactive is not aligned along with its value.
> 
> > +
> > +	reg = XDSI_TIME2_HACT((vm->hactive) * (dsi->mul_factor) / 100) |
> 
> Ditto. No ().
> 
> > +	      XDSI_TIME2_VACT(vm->vactive);
> > +	xlnx_dsi_writel(dsi->iomem, XDSI_TIME2, reg);
> > +
> > +	dev_dbg(dsi->dev, "LCD size = %dx%d\n", vm->hactive, vm->vactive);
> > +}
> > +
> > +/**
> > + * xlnx_dsi_set_display_enable - Enables the DSI Tx IP core enable
> > + * register bit
> > + * @dsi: Xilinx DSI structure
> > + *
> > + * This function takes the DSI strucure and enables the core enable bit
> > + * of core configuration register.
> > + */
> > +static void xlnx_dsi_set_display_enable(struct xlnx_dsi *dsi)
> > +{
> > +	u32 reg;
> > +
> > +	reg = xlnx_dsi_readl(dsi->iomem, XDSI_CCR);
> > +	reg |= XDSI_CCR_COREENB;
> > +
> 
> Nit. It can be less lines by removing this empty line and setting the reg
> at declarartion an so on.
> 
> > +	xlnx_dsi_writel(dsi->iomem, XDSI_CCR, reg);
> > +	dev_dbg(dsi->dev, "MIPI DSI Tx controller is enabled.\n");
> > +}
> > +
> > +/**
> > + * xlnx_dsi_set_display_disable - Disable the DSI Tx IP core enable
> > + * register bit
> > + * @dsi: Xilinx DSI structure
> > + *
> > + * This function takes the DSI strucure and disables the core enable bit
> > + * of core configuration register.
> > + */
> > +static void xlnx_dsi_set_display_disable(struct xlnx_dsi *dsi)
> > +{
> > +	u32 reg;
> > +
> > +	reg = xlnx_dsi_readl(dsi->iomem, XDSI_CCR);
> > +	reg &= ~XDSI_CCR_COREENB;
> > +
> 
> Ditto.
> 
> > +	xlnx_dsi_writel(dsi->iomem, XDSI_CCR, reg);
> > +	dev_dbg(dsi->dev, "DSI Tx is disabled. reset regs to default values\n");
> > +}
> > +
> > +/**
> > + * xlnx_dsi_host_transfer - transfer command to panel
> > + * @host: mipi dsi host structure
> > + * @msg: mipi dsi msg with type, length and data
> > + *
> > + * This function is valid only in command mode.
> > + * It checks the command fifo empty status and writes into
> > + * data or cmd register and waits for the completion status.
> > + *
> > + * Return:	number of bytes, on success and error number on failure
> 
> Nit. Extra spaces.
> 
> > + */
> > +static ssize_t xlnx_dsi_host_transfer(struct mipi_dsi_host *host,
> > +				      const struct mipi_dsi_msg *msg)
> > +{
> > +	struct xlnx_dsi *dsi = host_to_dsi(host);
> > +	u32 data0, data1, cmd0, status, val;
> > +	const char *tx_buf = msg->tx_buf;
> > +
> > +	if (!(xlnx_dsi_readl(dsi->iomem, XDSI_CCR) & (XDSI_CCR_COREENB |
> > +						      XDSI_CCR_CMDMODE))) {
> 
> This passes when one of these 2 bits is set, and I don't think it's right.
> 
> > +		dev_err(dsi->dev, "dsi command mode not enabled\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (msg->type == MIPI_DSI_DCS_LONG_WRITE) {
> > +		status = readl_poll_timeout(dsi->iomem + XDSI_STR, val,
> > +					    ((val & XDSI_STR_LPKT_MASK) ==
> > +					     XDSI_STR_LPKT_MASK), 1,
> 
> Please remove unneeded (). Same for rest below.
> 
> > +					    XDSI_CMD_TIMEOUT_VAL);
> 
> It'd be nice if these delay / timeout values are described..
> 
> > +		if (status) {
> > +			dev_err(dsi->dev, "long cmd fifo not empty!\n");
> > +			return -ETIMEDOUT;
> 
> Isn't this checking if the controller is ready for long packet transaction?
> Then maybe -EBUSY is better. For timeout, the 'status' can propagate.
> Same for below.
> 
> > +		}
> > +		data0 = tx_buf[0] | (tx_buf[1] << 8) | (tx_buf[2] << 16) |
> > +			(tx_buf[3] << 24);
> > +		data1 = tx_buf[4] | (tx_buf[5] << 8);
> > +		cmd0 = msg->type | (MIPI_DSI_DCS_READ << 8);
> > +
> > +		xlnx_dsi_writel(dsi->iomem, XDSI_DFR, data0);
> > +		xlnx_dsi_writel(dsi->iomem, XDSI_DFR, data1);
> > +		xlnx_dsi_writel(dsi->iomem, XDSI_CMD, cmd0);
> > +	} else {
> 
> I'm not familiar with DSI transaction handling, but is it safe to assume
> all other than long write is short packet write (param, without param)?
> 
> > +		data0 = tx_buf[0];
> 
> This line can be removed.
> 
> > +		if (msg->type == MIPI_DSI_DCS_SHORT_WRITE_PARAM)
> > +			data0 = MIPI_DSI_DCS_SHORT_WRITE_PARAM |
> > +				(tx_buf[0] << 8) | (tx_buf[1] << 16);
> > +		else
> > +			data0 = MIPI_DSI_DCS_SHORT_WRITE | (tx_buf[0] << 8);
> 
> I'd put () for this if - else statments, but it may be just me.
> 
> 
> Then, this can mvoe to right before xlnx_dsi_writel() below.
> 
> > +
> > +		status = readl_poll_timeout(dsi->iomem + XDSI_STR, val,
> > +					    ((val & XDSI_STR_RDY_SHPKT) ==
> > +					     XDSI_STR_RDY_SHPKT), 1,
> > +					    XDSI_CMD_TIMEOUT_VAL);
> > +		if (status) {
> > +			dev_err(dsi->dev, "short cmd fifo not empty\n");
> > +			return -ETIMEDOUT;
> > +		}
> > +		xlnx_dsi_writel(dsi->iomem, XDSI_CMD, data0);
> > +	}
> > +
> > +	status = readl_poll_timeout(dsi->iomem + XDSI_STR, val,
> > +				    (!(val & XDSI_STR_CMD_EXE_PGS)), 1,
> > +				    XDSI_CMD_TIMEOUT_VAL);
> > +	if (status) {
> > +		dev_err(dsi->dev, "cmd time out\n");
> > +		return -ETIMEDOUT;
> > +	}
> > +
> > +	return msg->tx_len;
> > +}
> > +
> > +static int xlnx_dsi_host_attach(struct mipi_dsi_host *host,
> > +				struct mipi_dsi_device *device)
> > +{
> > +	u32 panel_lanes;
> > +	struct xlnx_dsi *dsi = host_to_dsi(host);
> > +
> > +	panel_lanes = device->lanes;
> 
> I'd do this above,
> 
> 	u32 panel_lanes = device->lanes
> 
> > +	dsi->mode_flags = device->mode_flags;
> > +	dsi->panel_node = device->dev.of_node;
> > +
> > +	if (panel_lanes != dsi->lanes) {
> > +		dev_err(dsi->dev, "Mismatch of lanes. panel = %d, DSI = %d\n",
> > +			panel_lanes, dsi->lanes);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (device->format != dsi->format) {
> > +		dev_err(dsi->dev, "Mismatch of format. panel = %d, DSI = %d\n",
> > +			device->format, dsi->format);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (dsi->connector.dev)
> > +		drm_helper_hpd_irq_event(dsi->connector.dev);
> > +
> > +	return 0;
> > +}
> > +
> > +static int xlnx_dsi_host_detach(struct mipi_dsi_host *host,
> > +				struct mipi_dsi_device *device)
> > +{
> > +	struct xlnx_dsi *dsi = host_to_dsi(host);
> > +
> > +	if (dsi->panel) {
> > +		drm_panel_detach(dsi->panel);
> > +		dsi->panel = NULL;
> > +	}
> > +
> > +	if (dsi->connector.dev)
> > +		drm_helper_hpd_irq_event(dsi->connector.dev);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct mipi_dsi_host_ops xlnx_dsi_ops = {
> > +	.attach = xlnx_dsi_host_attach,
> > +	.detach = xlnx_dsi_host_detach,
> > +	.transfer = xlnx_dsi_host_transfer,
> > +};
> > +
> > +static int xlnx_dsi_connector_dpms(struct drm_connector *connector,
> > +				   int mode)
> > +{
> > +	struct xlnx_dsi *dsi = connector_to_dsi(connector);
> > +	int ret;
> > +
> > +	dev_dbg(dsi->dev, "connector dpms state: %d\n", mode);
> > +
> > +	switch (mode) {
> > +	case DRM_MODE_DPMS_ON:
> > +		ret = drm_panel_prepare(dsi->panel);
> > +		if (ret < 0) {
> > +			dev_err(dsi->dev, "DRM panel not found\n");
> > +			return ret;
> > +		}
> > +
> > +		ret = drm_panel_enable(dsi->panel);
> > +		if (ret < 0) {
> > +			drm_panel_unprepare(dsi->panel);
> > +			dev_err(dsi->dev, "DRM panel not enabled\n");
> > +			return ret;
> > +		}
> > +		break;
> > +	default:
> > +		drm_panel_disable(dsi->panel);
> > +		drm_panel_unprepare(dsi->panel);
> > +		break;
> > +	}
> > +
> > +	return drm_helper_connector_dpms(connector, mode);
> > +}
> > +
> > +static enum drm_connector_status
> > +xlnx_dsi_detect(struct drm_connector *connector, bool force)
> > +{
> > +	struct xlnx_dsi *dsi = connector_to_dsi(connector);
> > +
> > +	if (!dsi->panel) {
> > +		dsi->panel = of_drm_find_panel(dsi->panel_node);
> > +		if (dsi->panel) {
> > +			drm_panel_attach(dsi->panel, &dsi->connector);
> 
> Above are quite static, so can't it be done in host attach? Or do you see more
> dynamic use cases?
> 
> > +			if (dsi->cmdmode) {
> > +				xlnx_dsi_writel(dsi->iomem, XDSI_CCR,
> > +						XDSI_CCR_CMDMODE |
> > +						XDSI_CCR_COREENB);
> > +				drm_panel_prepare(dsi->panel);
> 
> Just to confirm, is this not needed for non-command mode? And how is this
> aligned with same call in dpms(), meaning the panel will be prepared
> twice in command mode.
> 
> > +				xlnx_dsi_writel(dsi->iomem, XDSI_CCR, 0);
> > +			}
> > +		}
> > +	} else if (!dsi->panel_node) {
> > +		xlnx_dsi_connector_dpms(connector, DRM_MODE_DPMS_OFF);
> > +		drm_panel_detach(dsi->panel);
> > +		dsi->panel = NULL;
> > +	}
> > +
> > +	if (dsi->panel)
> > +		return connector_status_connected;
> > +
> > +	return connector_status_disconnected;
> > +}
> > +
> > +static void xlnx_dsi_connector_destroy(struct drm_connector *connector)
> > +{
> > +	drm_connector_unregister(connector);
> > +	drm_connector_cleanup(connector);
> > +	connector->dev = NULL;
> > +}
> > +
> > +static const struct drm_connector_funcs xlnx_dsi_connector_funcs = {
> > +	.detect = xlnx_dsi_detect,
> > +	.fill_modes = drm_helper_probe_single_connector_modes,
> > +	.destroy = xlnx_dsi_connector_destroy,
> > +	.reset			= drm_atomic_helper_connector_reset,
> 
> This better indent more consistently. Please do it through the entire file.
> 
> > +	.atomic_duplicate_state	= drm_atomic_helper_connector_duplicate_state,
> > +	.atomic_destroy_state	= drm_atomic_helper_connector_destroy_state,
> > +	.dpms = xlnx_dsi_connector_dpms,
> > +};
> > +
> > +static int xlnx_dsi_get_modes(struct drm_connector *connector)
> > +{
> > +	struct xlnx_dsi *dsi = connector_to_dsi(connector);
> > +
> > +	if (dsi->panel)
> > +		return drm_panel_get_modes(dsi->panel, connector);
> > +
> > +	return 0;
> > +}
> > +
> > +static struct drm_encoder *
> > +xlnx_dsi_best_encoder(struct drm_connector *connector)
> > +{
> > +	return &(connector_to_dsi(connector)->encoder);
> > +}
> > +
> > +static const struct drm_connector_helper_funcs
> > +xlnx_dsi_connector_helper_funcs = {
> > +	.get_modes = xlnx_dsi_get_modes,
> > +	.best_encoder = xlnx_dsi_best_encoder,
> > +};
> > +
> > +static int xlnx_dsi_create_connector(struct drm_encoder *encoder)
> > +{
> > +	struct xlnx_dsi *dsi = encoder_to_dsi(encoder);
> > +	struct drm_connector *connector = &dsi->connector;
> > +	struct drm_device *drm = encoder->dev;
> > +	int ret;
> > +
> > +	connector->polled = DRM_CONNECTOR_POLL_HPD;
> > +
> > +	ret = drm_connector_init(encoder->dev, connector,
> > +				 &xlnx_dsi_connector_funcs,
> > +				 DRM_MODE_CONNECTOR_DSI);
> > +	if (ret) {
> > +		dev_err(dsi->dev, "Failed to initialize connector with drm\n");
> > +		return ret;
> > +	}
> > +
> > +	drm_connector_helper_add(connector, &xlnx_dsi_connector_helper_funcs);
> > +	drm_connector_attach_encoder(connector, encoder);
> > +	if (!drm->registered)
> > +		return 0;
> > +
> > +	drm_connector_register(connector);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * xlnx_dsi_atomic_mode_set -  derive the DSI timing parameters
> > + *
> > + * @encoder: pointer to Xilinx DRM encoder
> > + * @crtc_state: Pointer to drm core crtc state
> > + * @connector_state: DSI connector drm state
> > + *
> > + * This function derives the DSI IP timing parameters from the timing
> > + * values given in the attached panel driver.
> > + */
> > +static void
> > +xlnx_dsi_atomic_mode_set(struct drm_encoder *encoder,
> > +			 struct drm_crtc_state *crtc_state,
> > +				 struct drm_connector_state *connector_state)
> > +{
> > +	struct xlnx_dsi *dsi = encoder_to_dsi(encoder);
> > +	struct videomode *vm = &dsi->vm;
> > +	struct drm_display_mode *m = &crtc_state->adjusted_mode;
> > +
> > +	vm->hactive = m->hdisplay;
> > +	vm->vactive = m->vdisplay;
> > +	vm->vfront_porch = m->vsync_start - m->vdisplay;
> > +	vm->vback_porch = m->vtotal - m->vsync_end;
> > +	vm->vsync_len = m->vsync_end - m->vsync_start;
> > +	vm->hfront_porch = m->hsync_start - m->hdisplay;
> > +	vm->hback_porch = m->htotal - m->hsync_end;
> > +	vm->hsync_len = m->hsync_end - m->hsync_start;
> > +	xlnx_dsi_set_display_mode(dsi);
> 
> As commented above, this doesn't have to be re-directed through videomode.
> Then the function can be inlined here.
> 
> > +}
> > +
> > +static void xlnx_dsi_disable(struct drm_encoder *encoder)
> > +{
> > +	struct xlnx_dsi *dsi = encoder_to_dsi(encoder);
> > +
> > +	xlnx_dsi_set_display_disable(dsi);
> 
> 	xlnx_dsi_set_display_disable(encoder_to_dsi(encoder));
> 
> Maybe even this wrapper can be removed?
> 
> > +}
> > +
> > +static void xlnx_dsi_enable(struct drm_encoder *encoder)
> > +{
> > +	struct xlnx_dsi *dsi = encoder_to_dsi(encoder);
> > +
> > +	xlnx_dsi_set_display_enable(dsi);
> 
> Ditto.
> 
> > +}
> > +
> > +static const struct drm_encoder_helper_funcs
> > +xlnx_dsi_encoder_helper_funcs = {
> > +	.atomic_mode_set = xlnx_dsi_atomic_mode_set,
> > +	.enable = xlnx_dsi_enable,
> > +	.disable = xlnx_dsi_disable,
> > +};
> > +
> > +static const struct drm_encoder_funcs xlnx_dsi_encoder_funcs = {
> > +	.destroy = drm_encoder_cleanup,
> > +};
> > +
> > +static int xlnx_dsi_parse_dt(struct xlnx_dsi *dsi)
> > +{
> > +	struct device *dev = dsi->dev;
> > +	struct device_node *node = dev->of_node;
> > +	int ret;
> > +	u32 datatype;
> > +	static const int xdsi_mul_fact[XDSI_NUM_DATA_T] = {300, 225, 225, 200};
> > +
> > +	dsi->dphy_clk_200M = devm_clk_get(dev, "dphy_clk_200M");
> > +	if (IS_ERR(dsi->dphy_clk_200M)) {
> > +		ret = PTR_ERR(dsi->dphy_clk_200M);
> > +		dev_err(dev, "failed to get dphy_clk_200M %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	dsi->video_aclk = devm_clk_get(dev, "s_axis_aclk");
> > +	if (IS_ERR(dsi->video_aclk)) {
> > +		ret = PTR_ERR(dsi->video_aclk);
> > +		dev_err(dev, "failed to get video_clk %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	ret = of_property_read_u32(node, "xlnx,dsi-num-lanes", &dsi->lanes);
> > +	if (ret < 0) {
> > +		dev_err(dsi->dev, "missing xlnx,dsi-num-lanes property\n");
> > +		return ret;
> > +	}
> > +	if (dsi->lanes > 4 || dsi->lanes < 1) {
> > +		dev_err(dsi->dev, "%d lanes : invalid lanes\n", dsi->lanes);
> > +		return -EINVAL;
> > +	}
> 
> Nit. An empty line here would be helpful for readability.
> 
> > +	ret = of_property_read_u32(node, "xlnx,dsi-data-type", &datatype);
> > +	if (ret < 0) {
> > +		dev_err(dsi->dev, "missing xlnx,dsi-data-type property\n");
> > +		return ret;
> > +	}
> > +	dsi->format = datatype;
> > +	if (datatype > MIPI_DSI_FMT_RGB565) {
> > +		dev_err(dsi->dev, "Invalid xlnx,dsi-data-type string\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	/*
> > +	 * multiplication factor used for HACT, based on data type.
> > +	 *
> > +	 * e.g. for RGB666_L datatype and 1920x1080 resolution,
> > +	 * the Hact (WC) would be as follows -
> > +	 * 1920 pixels * 18 bits per pixel / 8 bits per byte
> > +	 * = 1920 pixels * 2.25 bytes per pixel = 4320 bytes.
> > +	 *
> > +	 * Data Type - Multiplication factor
> > +	 * RGB888    - 3
> > +	 * RGB666_L  - 2.25
> > +-	 * RGB666_P  - 2.25
> > +	 * RGB565    - 2
> > +	 *
> > +	 * Since the multiplication factor maybe a floating number,
> > +	 * a 100x multiplication factor is used.
> > +	 */
> > +	dsi->mul_factor = xdsi_mul_fact[datatype];
> > +
> > +	dsi->cmdmode = of_property_read_bool(node, "xlnx,dsi-cmd-mode");
> > +
> > +	dev_dbg(dsi->dev, "DSI controller num lanes = %d", dsi->lanes);
> > +	dev_dbg(dsi->dev, "DSI controller datatype = %d\n", datatype);
> > +	dev_dbg(dsi->dev, "DSI controller cmd mode = %d\n", dsi->cmdmode);
> > +
> > +	return 0;
> > +}
> > +
> > +static int xlnx_dsi_bind(struct device *dev, struct device *master,
> > +			 void *data)
> > +{
> > +	struct xlnx_dsi *dsi = dev_get_drvdata(dev);
> > +	struct drm_encoder *encoder = &dsi->encoder;
> > +	struct drm_device *drm_dev = data;
> > +	int ret;
> > +
> > +	drm_encoder_init(drm_dev, encoder, &xlnx_dsi_encoder_funcs,
> > +			 DRM_MODE_ENCODER_DSI, NULL);
> > +	drm_encoder_helper_add(encoder, &xlnx_dsi_encoder_helper_funcs);
> > +
> > +	encoder->possible_crtcs = 1;
> > +
> > +	ret = xlnx_dsi_create_connector(encoder);
> > +	if (ret) {
> > +		dev_err(dsi->dev, "fail creating connector, ret = %d\n", ret);
> > +		drm_encoder_cleanup(encoder);
> > +		return ret;
> > +	}
> > +
> > +	ret = mipi_dsi_host_register(&dsi->dsi_host);
> > +	if (ret < 0) {
> 
> Just nit. if (ret) would do.
> 
> > +		dev_err(dsi->dev, "failed to register DSI host: %d\n", ret);
> > +		xlnx_dsi_connector_destroy(&dsi->connector);
> > +		drm_encoder_cleanup(encoder);
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void xlnx_dsi_unbind(struct device *dev, struct device *master,
> > +			    void *data)
> > +{
> > +	struct xlnx_dsi *dsi = dev_get_drvdata(dev);
> > +
> > +	xlnx_dsi_disable(&dsi->encoder);
> > +	mipi_dsi_host_unregister(&dsi->dsi_host);
> > +}
> > +
> > +static const struct component_ops xlnx_dsi_component_ops = {
> > +	.bind	= xlnx_dsi_bind,
> > +	.unbind	= xlnx_dsi_unbind,
> > +};
> > +
> > +static int xlnx_dsi_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct resource *res;
> > +	struct xlnx_dsi *dsi;
> > +	int ret;
> > +	unsigned long rate;
> > +
> > +	dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> > +	if (!dsi)
> > +		return -ENOMEM;
> > +
> > +	dsi->dsi_host.ops = &xlnx_dsi_ops;
> > +	dsi->dsi_host.dev = dev;
> > +	dsi->dev = dev;
> > +
> > +	ret = xlnx_dsi_parse_dt(dsi);
> > +	if (ret)
> > +		return ret;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	dsi->iomem = devm_ioremap_resource(dev, res);
> > +	if (IS_ERR(dsi->iomem)) {
> > +		dev_err(dev, "failed to remap io region\n");
> > +		return PTR_ERR(dsi->iomem);
> > +	}
> > +	platform_set_drvdata(pdev, dsi);
> > +
> > +	ret = clk_set_rate(dsi->dphy_clk_200M, XDSI_DPHY_CLK_REQ);
> > +	if (ret) {
> > +		dev_err(dev, "failed to set dphy clk rate %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	ret = clk_prepare_enable(dsi->dphy_clk_200M);
> > +	if (ret) {
> > +		dev_err(dev, "failed to enable dphy clk %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	rate = clk_get_rate(dsi->dphy_clk_200M);
> > +	if (rate < XDSI_DPHY_CLK_MIN && rate > XDSI_DPHY_CLK_MAX) {
> 
> A brief comment for this line wold be helpful.
> 
> > +		dev_err(dev, "Error DPHY clock = %lu\n", rate);
> > +		ret = -EINVAL;
> > +		goto err_disable_dphy_clk;
> > +	}
> > +
> > +	ret = clk_prepare_enable(dsi->video_aclk);
> > +	if (ret) {
> > +		dev_err(dev, "failed to enable video clk %d\n", ret);
> > +		goto err_disable_dphy_clk;
> > +	}
> > +
> > +	ret = component_add(dev, &xlnx_dsi_component_ops);

The driver should expose the DSI-TX as a drm_bridge instead of using the
component framework. You shouldn't register a drm_encoder, and I don't
think you should register a drm_connector either. Only bridge operations
should be exposed, and the drm_bridge .attach() operation should return
an error when DRM_BRIDGE_ATTACH_NO_CONNECTOR is not set. The top-level
driver using this bridge should create the drm_encoder and
drm_connector, most likely using drm_bridge_connector_init() to create
the connector.

> > +	if (ret < 0)
> 
> I prefer if (ret) where possible, but it may be just me. I let you decide.
> 
> > +		goto err_disable_video_clk;
> > +
> > +	return ret;
> 
> return 0;? but up to you.
> 
> > +
> > +err_disable_video_clk:
> > +	clk_disable_unprepare(dsi->video_aclk);
> > +err_disable_dphy_clk:
> > +	clk_disable_unprepare(dsi->dphy_clk_200M);
> > +	return ret;
> > +}
> 
> At least, this initial one better come with a complete display pipeline,
> ex crtc / plane are missing. This won't be functional without those.
> I believe Laurent was planning to make the xlnx drm layer as a library,
> so hopefully this can be a good starting point and come with drivers aligned
> with it.
> 
> > +
> > +static int xlnx_dsi_remove(struct platform_device *pdev)
> > +{
> > +	struct xlnx_dsi *dsi = platform_get_drvdata(pdev);
> > +
> > +	component_del(&pdev->dev, &xlnx_dsi_component_ops);
> > +	clk_disable_unprepare(dsi->video_aclk);
> > +	clk_disable_unprepare(dsi->dphy_clk_200M);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id xlnx_dsi_of_match[] = {
> > +	{ .compatible = "xlnx-dsi", },
> 
> This should change. I believe it should be something like, xlnx,<dsi ip name>-<version>
> 
> > +	{ /* end of table */ },
> > +};
> > +MODULE_DEVICE_TABLE(of, xlnx_dsi_of_match);
> > +
> > +static struct platform_driver dsi_driver = {
> > +	.probe = xlnx_dsi_probe,
> > +	.remove = xlnx_dsi_remove,
> > +	.driver = {
> > +		.name = "xlnx-dsi",
> > +		.of_match_table = xlnx_dsi_of_match,
> > +	},
> > +};
> > +
> > +module_platform_driver(dsi_driver);
> > +
> > +MODULE_AUTHOR("Xilinx, Inc.");
> > +MODULE_DESCRIPTION("Xilinx FPGA MIPI DSI Tx Driver");
> > +MODULE_LICENSE("GPL v2");

-- 
Regards,

Laurent Pinchart