[PATCH 4/6] video: add i.MX8MP LCDIF2 V8 framebuffer driver
Ahmad Fatoum
a.fatoum at pengutronix.de
Tue Jun 2 00:16:16 PDT 2026
Hello,
On 6/2/26 6:09 AM, Johannes Schneider wrote:
> From: Thomas Haemmerle <thomas.haemmerle at leica-geosystems.com>
>
> The i.MX8MP has a new LCDIF V8 display controller with a different
> register layout from the older mxsfb-based LCDIF found on i.MX6/7/8MM.
> The existing DRIVER_VIDEO_LCDIF driver does not support this variant,
> leaving the i.MX8MP without a barebox framebuffer and no way to show a
> boot splash.
>
> The driver:
> - Programs LCDIF V8 timing registers for the configured video mode.
> - Uses 128B DMA burst size (P_SIZE=1, T_SIZE=1) so that 800-pixel rows
> (3200 bytes) divide into exactly 25 complete bursts; 256B bursts leave
> a partial burst and produce a ~32px black strip at the right edge.
> - Sets correct CTRL polarity bit positions (INV_HS=bit0, INV_VS=bit1,
> INV_DE=bit2, INV_PXCK=bit3); the i.MX8MP TRM places these at bits 0-3,
> not 2-5 as a naive port from mxsfb would suggest.
> - Allocates a write-combine DMA framebuffer and registers a simplefb DT
> fixup for Linux DRM_SIMPLEDRM to inherit the boot image.
> - Enables the framebuffer at probe time so the splash command only needs
> to blit pixels; fb_enable() is not called per-splash.
>
> Assisted-by: Claude:claude-sonnet-4-6
> Signed-of-by: Thomas Haemmerle <thomas.haemmerle at leica-geosystems.com>
Michael had introduced this driver already into barebox v2026.01.0, see
drivers/video/lcdif_drv.c.
It matches both i.MX8MP and i.MX93 already, but has been tested only on
i.MX93 so far as I am aware.
Please try again with the upstream driver and extend it as needed.
Cheers,
Ahmad
> ---
> drivers/video/Kconfig | 10 +
> drivers/video/Makefile | 1 +
> drivers/video/imx-lcdif.c | 378 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 389 insertions(+)
> create mode 100644 drivers/video/imx-lcdif.c
>
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index ce10237221..fbcec6fd67 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -194,6 +194,16 @@ config DRIVER_VIDEO_TC358767
> help
> The TC358767A is a DSI/DPI to eDP video encoder chip
>
> +config DRIVER_VIDEO_IMX_LCDIF
> + bool "i.MX8MP LCDIF V8 framebuffer driver"
> + select VIDEO_VPL
> + select DRIVER_VIDEO_SIMPLEFB
> + depends on OFTREE && OFDEVICE
> + help
> + Framebuffer driver for the i.MX8MP/i.MX93 LCDIF V8 display controller.
> + Supports the "fsl,imx8mp-lcdif" compatible. Creates a simple-framebuffer
> + device tree node for kernel handoff via DRM_SIMPLEDRM.
> +
> config DRIVER_VIDEO_SIMPLE_PANEL
> bool "Simple panel support"
> select VIDEO_VPL
> diff --git a/drivers/video/Makefile b/drivers/video/Makefile
> index 7b10eda0d8..9957ff5ad2 100644
> --- a/drivers/video/Makefile
> +++ b/drivers/video/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_FRAMEBUFFER_CONSOLE) += fbconsole.o
> obj-$(CONFIG_VIDEO_VPL) += vpl.o
> obj-$(CONFIG_DRIVER_VIDEO_MTL017) += mtl017.o
> obj-$(CONFIG_DRIVER_VIDEO_TC358767) += tc358767.o
> +obj-$(CONFIG_DRIVER_VIDEO_IMX_LCDIF) += imx-lcdif.o
> obj-$(CONFIG_DRIVER_VIDEO_SIMPLE_PANEL) += simple-panel.o
> obj-$(CONFIG_DRIVER_VIDEO_MIPI_DBI) += mipi_dbi.o
> obj-$(CONFIG_DRIVER_VIDEO_MIPI_DSI) += mipi_dsi.o
> diff --git a/drivers/video/imx-lcdif.c b/drivers/video/imx-lcdif.c
> new file mode 100644
> index 0000000000..ae5976c771
> --- /dev/null
> +++ b/drivers/video/imx-lcdif.c
> @@ -0,0 +1,378 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * i.MX8MP LCDIF V8 framebuffer driver for barebox
> + *
> + * Based on Linux drivers/gpu/drm/mxsfb/lcdif_drv.c and lcdif_kms.c
> + * Copyright (C) 2022 Marek Vasut <marex at denx.de>
> + *
> + * Copyright Leica Geosystems AG
> + */
> +
> +#include <common.h>
> +#include <init.h>
> +#include <driver.h>
> +#include <io.h>
> +#include <dma.h>
> +#include <fb.h>
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <of_graph.h>
> +#include <video/media-bus-format.h>
> +#include <video/vpl.h>
> +
> +/* LCDIF V8 register map */
> +#define LCDC_V8_CTRL 0x00
> +#define LCDC_V8_DISP_PARA 0x10
> +#define LCDC_V8_DISP_SIZE 0x14
> +#define LCDC_V8_HSYN_PARA 0x18
> +#define LCDC_V8_VSYN_PARA 0x1c
> +#define LCDC_V8_VSYN_HSYN_WIDTH 0x20
> +#define LCDC_V8_INT_STATUS_D0 0x24
> +#define LCDC_V8_INT_ENABLE_D0 0x28
> +#define LCDC_V8_INT_STATUS_D1 0x30
> +#define LCDC_V8_INT_ENABLE_D1 0x34
> +#define LCDC_V8_CTRLDESCL0_1 0x200
> +#define LCDC_V8_CTRLDESCL0_3 0x208
> +#define LCDC_V8_CTRLDESCL_LOW0_4 0x20c
> +#define LCDC_V8_CTRLDESCL_HIGH0_4 0x210
> +#define LCDC_V8_CTRLDESCL0_5 0x214
> +#define LCDC_V8_CSC0_CTRL 0x21c
> +#define LCDC_V8_PANIC0_THRES 0x238
> +
> +/* CTRL bits */
> +#define CTRL_SW_RESET BIT(31)
> +#define CTRL_FETCH_START_OPTION_FPV 0
> +#define CTRL_INV_HS BIT(0)
> +#define CTRL_INV_VS BIT(1)
> +#define CTRL_INV_DE BIT(2)
> +#define CTRL_INV_PXCK BIT(3)
> +
> +/* DISP_PARA bits */
> +#define DISP_PARA_DISP_ON BIT(31)
> +#define DISP_PARA_LINE_PATTERN_RGB888 (0x0 << 26)
> +#define DISP_PARA_LINE_PATTERN_UYVY (0x3 << 26)
> +#define DISP_PARA_LINE_PATTERN_MASK GENMASK(29, 26)
> +
> +/* DISP_SIZE: Y[31:16] X[15:0] */
> +#define DISP_SIZE_DELTA_Y(y) (((y) & 0xffff) << 16)
> +#define DISP_SIZE_DELTA_X(x) ((x) & 0xffff)
> +
> +/* HSYN_PARA: back_porch[31:16] front_porch[15:0] */
> +#define HSYN_PARA_BP_H(bp) (((bp) & 0xffff) << 16)
> +#define HSYN_PARA_FP_H(fp) ((fp) & 0xffff)
> +
> +/* VSYN_PARA: back_porch[31:16] front_porch[15:0] */
> +#define VSYN_PARA_BP_V(bp) (((bp) & 0xffff) << 16)
> +#define VSYN_PARA_FP_V(fp) ((fp) & 0xffff)
> +
> +/* VSYN_HSYN_WIDTH: vsync[31:16] hsync[15:0] */
> +#define VSYN_HSYN_WIDTH_PW_V(v) (((v) & 0xffff) << 16)
> +#define VSYN_HSYN_WIDTH_PW_H(h) ((h) & 0xffff)
> +
> +/* CTRLDESCL0_1: height[31:16] width[15:0] */
> +#define CTRLDESCL0_1_HEIGHT(h) (((h) & 0xffff) << 16)
> +#define CTRLDESCL0_1_WIDTH(w) ((w) & 0xffff)
> +
> +/* CTRLDESCL0_3: P_SIZE[22:20] T_SIZE[17:16] PITCH[15:0] */
> +#define CTRLDESCL0_3_P_SIZE(s) (((s) & 0x7) << 20)
> +#define CTRLDESCL0_3_T_SIZE(s) (((s) & 0x3) << 16)
> +#define CTRLDESCL0_3_PITCH(p) ((p) & 0xffff)
> +
> +/* CTRLDESCL0_5 */
> +#define CTRLDESCL0_5_EN BIT(31)
> +#define CTRLDESCL0_5_SHADOW_LOAD_EN BIT(30)
> +#define CTRLDESCL0_5_BPP_16_RGB565 (0x4 << 24)
> +#define CTRLDESCL0_5_BPP_24_RGB888 (0x8 << 24)
> +#define CTRLDESCL0_5_BPP_32_ARGB8888 (0x9 << 24)
> +#define CTRLDESCL0_5_BPP_MASK GENMASK(27, 24)
> +
> +/* CSC0_CTRL */
> +#define CSC0_CTRL_BYPASS BIT(0)
> +
> +/* INT_ENABLE_D1 */
> +#define INT_ENABLE_D1_PLANE_PANIC_EN BIT(0)
> +
> +/* PANIC0_THRES */
> +#define PANIC0_THRES_LOW_MASK GENMASK(8, 0)
> +#define PANIC0_THRES_HIGH_MASK GENMASK(24, 16)
> +#define PANIC0_THRES_MAX 511
> +
> +struct lcdif_priv {
> + void __iomem *base;
> + struct clk *clk_pix;
> + struct clk *clk_axi;
> + struct clk *clk_disp_axi;
> + struct fb_info info;
> + struct vpl vpl;
> + int port_id;
> +};
> +
> +static void lcdif_reset(struct lcdif_priv *priv)
> +{
> + writel(CTRL_SW_RESET, priv->base + LCDC_V8_CTRL);
> + udelay(10);
> + writel(0, priv->base + LCDC_V8_CTRL);
> +}
> +
> +static void lcdif_set_mode(struct lcdif_priv *priv, struct fb_videomode *mode)
> +{
> + u32 ctrl = 0;
> +
> + if (mode->sync & FB_SYNC_HOR_HIGH_ACT)
> + ; /* HSYNC active high = no invert */
> + else
> + ctrl |= CTRL_INV_HS;
> +
> + if (mode->sync & FB_SYNC_VERT_HIGH_ACT)
> + ; /* VSYNC active high = no invert */
> + else
> + ctrl |= CTRL_INV_VS;
> +
> + if (mode->display_flags & DISPLAY_FLAGS_DE_LOW)
> + ctrl |= CTRL_INV_DE;
> + if (mode->display_flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
> + ctrl |= CTRL_INV_PXCK;
> +
> + writel(ctrl, priv->base + LCDC_V8_CTRL);
> +
> + writel(DISP_SIZE_DELTA_Y(mode->yres) | DISP_SIZE_DELTA_X(mode->xres),
> + priv->base + LCDC_V8_DISP_SIZE);
> +
> + /* hback_porch = htotal - hsync_end, hfront_porch = hsync_start - hactive */
> + writel(HSYN_PARA_BP_H(mode->left_margin) | HSYN_PARA_FP_H(mode->right_margin),
> + priv->base + LCDC_V8_HSYN_PARA);
> +
> + writel(VSYN_PARA_BP_V(mode->upper_margin) | VSYN_PARA_FP_V(mode->lower_margin),
> + priv->base + LCDC_V8_VSYN_PARA);
> +
> + writel(VSYN_HSYN_WIDTH_PW_V(mode->vsync_len) | VSYN_HSYN_WIDTH_PW_H(mode->hsync_len),
> + priv->base + LCDC_V8_VSYN_HSYN_WIDTH);
> +
> + writel(CTRLDESCL0_1_HEIGHT(mode->yres) | CTRLDESCL0_1_WIDTH(mode->xres),
> + priv->base + LCDC_V8_CTRLDESCL0_1);
> +}
> +
> +static void lcdif_set_plane(struct lcdif_priv *priv)
> +{
> + struct fb_info *info = &priv->info;
> + phys_addr_t paddr = virt_to_phys(info->screen_base);
> + u32 ctrl;
> + u32 stride = info->line_length;
> +
> + /*
> + * AXI burst size: P_SIZE=1 = 128B, T_SIZE=1 = 128B threshold.
> + * Use 128B (32-pixel @ 32bpp) bursts so that 800-pixel rows
> + * (3200 bytes) divide evenly: 3200 / 128 = 25 complete bursts.
> + * P_SIZE=2 (256B) would leave a partial burst (3200/256 = 12.5)
> + * causing a ~32-pixel dark gap at the right edge of the display.
> + */
> + ctrl = CTRLDESCL0_3_P_SIZE(1) | CTRLDESCL0_3_T_SIZE(1) |
> + CTRLDESCL0_3_PITCH(stride);
> + writel(ctrl, priv->base + LCDC_V8_CTRLDESCL0_3);
> +
> + writel(lower_32_bits(paddr), priv->base + LCDC_V8_CTRLDESCL_LOW0_4);
> + writel(upper_32_bits(paddr), priv->base + LCDC_V8_CTRLDESCL_HIGH0_4);
> +
> + /* 32bpp XRGB8888 → ARGB8888 pixel format.
> + * SHADOW_LOAD_EN causes the descriptor registers (address, format, pitch)
> + * to be latched into the active registers on the next VSYNC, which is
> + * required for the initial descriptor load in barebox's single-enable
> + * sequence (no DRM page-flip mechanism). EN is ORed in later by
> + * lcdif_enable() after DISP_ON. */
> + writel(CTRLDESCL0_5_BPP_32_ARGB8888 | CTRLDESCL0_5_SHADOW_LOAD_EN,
> + priv->base + LCDC_V8_CTRLDESCL0_5);
> +}
> +
> +static void lcdif_enable(struct lcdif_priv *priv)
> +{
> + u32 reg;
> +
> + /* Set FIFO Panic watermarks: low=1/3, high=2/3 */
> + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_MAX / 3) |
> + FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_MAX / 3),
> + priv->base + LCDC_V8_PANIC0_THRES);
> +
> + writel(INT_ENABLE_D1_PLANE_PANIC_EN, priv->base + LCDC_V8_INT_ENABLE_D1);
> +
> + /* Write LINE_PATTERN_RGB888 (= 0) first to clear all DISP_PARA bits,
> + * including BGND_R/G/B (bits [23:0]) — ensures background is black. */
> + writel(DISP_PARA_LINE_PATTERN_RGB888, priv->base + LCDC_V8_DISP_PARA);
> + reg = readl(priv->base + LCDC_V8_DISP_PARA);
> + reg |= DISP_PARA_DISP_ON;
> + writel(reg, priv->base + LCDC_V8_DISP_PARA);
> +
> + reg = readl(priv->base + LCDC_V8_CTRLDESCL0_5);
> + reg |= CTRLDESCL0_5_EN;
> + writel(reg, priv->base + LCDC_V8_CTRLDESCL0_5);
> +}
> +
> +static int lcdif_fb_enable(struct fb_info *info)
> +{
> + struct lcdif_priv *priv = info->priv;
> + struct fb_videomode *mode = info->mode;
> + int ret;
> +
> + clk_set_rate(priv->clk_pix, PICOS2KHZ(mode->pixclock) * 1000UL);
> + clk_prepare_enable(priv->clk_axi);
> + clk_prepare_enable(priv->clk_disp_axi);
> + clk_prepare_enable(priv->clk_pix);
> +
> + /* Notify downstream bridge about mode and enable it */
> + ret = vpl_ioctl_prepare(&priv->vpl, priv->port_id, mode);
> + if (ret) {
> + dev_err(info->dev.parent, "vpl_prepare failed: %pe\n", ERR_PTR(ret));
> + return ret;
> + }
> + lcdif_reset(priv);
> + lcdif_set_mode(priv, mode);
> + lcdif_set_plane(priv);
> +
> + /* Bypass CSC for RGB input */
> + writel(CSC0_CTRL_BYPASS, priv->base + LCDC_V8_CSC0_CTRL);
> +
> + lcdif_enable(priv);
> +
> + ret = vpl_ioctl_enable(&priv->vpl, priv->port_id);
> + if (ret)
> + dev_warn(info->dev.parent, "vpl_enable failed: %pe\n", ERR_PTR(ret));
> +
> + return 0;
> +}
> +
> +static void lcdif_fb_disable(struct fb_info *info)
> +{
> + struct lcdif_priv *priv = info->priv;
> + u32 reg;
> +
> + vpl_ioctl_disable(&priv->vpl, priv->port_id);
> +
> + reg = readl(priv->base + LCDC_V8_CTRLDESCL0_5);
> + reg &= ~CTRLDESCL0_5_EN;
> + writel(reg, priv->base + LCDC_V8_CTRLDESCL0_5);
> +
> + reg = readl(priv->base + LCDC_V8_DISP_PARA);
> + reg &= ~DISP_PARA_DISP_ON;
> + writel(reg, priv->base + LCDC_V8_DISP_PARA);
> +
> + vpl_ioctl_unprepare(&priv->vpl, priv->port_id);
> +
> + clk_disable_unprepare(priv->clk_pix);
> + clk_disable_unprepare(priv->clk_disp_axi);
> + clk_disable_unprepare(priv->clk_axi);
> +}
> +
> +static struct fb_ops lcdif_fb_ops = {
> + .fb_enable = lcdif_fb_enable,
> + .fb_disable = lcdif_fb_disable,
> +};
> +
> +static int lcdif_probe(struct device *dev)
> +{
> + struct resource *iores;
> + struct lcdif_priv *priv;
> + struct fb_info *info;
> + int ret;
> +
> + iores = dev_request_mem_resource(dev, 0);
> + if (IS_ERR(iores))
> + return PTR_ERR(iores);
> +
> + priv = xzalloc(sizeof(*priv));
> + priv->base = IOMEM(iores->start);
> +
> + priv->clk_pix = clk_get(dev, "pix");
> + if (IS_ERR(priv->clk_pix))
> + return dev_errp_probe(dev, priv->clk_pix, "pixel clock\n");
> +
> + priv->clk_axi = clk_get(dev, "axi");
> + if (IS_ERR(priv->clk_axi))
> + return dev_errp_probe(dev, priv->clk_axi, "axi clock\n");
> +
> + priv->clk_disp_axi = clk_get(dev, "disp_axi");
> + if (IS_ERR(priv->clk_disp_axi))
> + return dev_errp_probe(dev, priv->clk_disp_axi, "disp_axi clock\n");
> +
> + /* Register VPL node - endpoint is port at 0 */
> + priv->port_id = 0;
> + priv->vpl.node = dev->of_node;
> + ret = vpl_register(&priv->vpl);
> + if (ret)
> + return ret;
> +
> + info = &priv->info;
> + info->priv = priv;
> + info->fbops = &lcdif_fb_ops;
> +
> + /* Fixed 32bpp XRGB8888 format */
> + info->bits_per_pixel = 32;
> + info->red = (struct fb_bitfield){ .offset = 16, .length = 8 };
> + info->green = (struct fb_bitfield){ .offset = 8, .length = 8 };
> + info->blue = (struct fb_bitfield){ .offset = 0, .length = 8 };
> + info->transp = (struct fb_bitfield){ .offset = 24, .length = 8 };
> +
> + /* Get display modes from downstream panel via VPL */
> + ret = vpl_ioctl(&priv->vpl, priv->port_id, VPL_GET_VIDEOMODES, &info->modes);
> + if (ret) {
> + dev_dbg(dev, "no modes from VPL: %pe\n", ERR_PTR(ret));
> + return ret;
> + }
> +
> + /* Allocate DMA-coherent framebuffer */
> + if (info->modes.num_modes > 0) {
> + struct fb_videomode *m = &info->modes.modes[0];
> + size_t fb_size = m->xres * m->yres * (info->bits_per_pixel / 8);
> +
> + info->screen_base = dma_alloc_writecombine(DMA_DEVICE_BROKEN,
> + fb_size,
> + DMA_ADDRESS_BROKEN);
> + if (!info->screen_base) {
> + dev_err(dev, "failed to allocate framebuffer\n");
> + return -ENOMEM;
> + }
> + info->screen_size = fb_size;
> + memset(info->screen_base, 0, fb_size);
> + }
> +
> + info->dev.parent = dev;
> + ret = register_framebuffer(info);
> + if (ret) {
> + dev_err(dev, "failed to register framebuffer: %d\n", ret);
> + return ret;
> + }
> +
> + /*
> + * Create simple-framebuffer DT node for Linux kernel handoff.
> + * With CONFIG_DRM_SIMPLEDRM, Linux will inherit the barebox
> + * framebuffer and keep the boot splash visible until platsch
> + * renders via the LCDIF DRM driver.
> + */
> + info->register_simplefb = 1;
> + fb_register_simplefb(info);
> +
> + /*
> + * Enable the display immediately so the framebuffer is live.
> + * The splash command only blits pixels to the buffer - it does not
> + * call fb_enable itself - so we must enable here during probe.
> + */
> + ret = fb_enable(info);
> + if (ret)
> + dev_warn(dev, "failed to enable framebuffer: %d\n", ret);
> +
> + dev_info(dev, "i.MX8MP LCDIF registered\n");
> + return 0;
> +}
> +
> +static const struct of_device_id lcdif_dt_ids[] = {
> + { .compatible = "fsl,imx8mp-lcdif" },
> + { .compatible = "fsl,imx93-lcdif" },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, lcdif_dt_ids);
> +
> +static struct driver lcdif_driver = {
> + .name = "imx-lcdif",
> + .probe = lcdif_probe,
> + .of_compatible = DRV_OF_COMPAT(lcdif_dt_ids),
> +};
> +device_platform_driver(lcdif_driver);
--
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