Partially revert "video: fbdev: amba-clcd: Retire elder CLCD driver"

Also partially revert the follow-up change "drm: pl111: Absorb the
external register header".

This reverts the parts of commits
7e4e589db76a3cf4c1f534eb5a09cc6422766b93 and
0fb8125635e8eb5483fb095f98dcf0651206a7b8 that touch paths outside
of drivers/gpu/drm/pl111.

The fbdev driver is used by Android's FVP configuration. Using the
DRM driver together with DRM's fbdev emulation results in a failure
to boot Android. The root cause is that Android's generic fbdev
userspace driver relies on the ability to set the pixel format via
FBIOPUT_VSCREENINFO, which is not supported by fbdev emulation.

There have been other less critical behavioral differences identified
between the fbdev driver and the DRM driver with fbdev emulation. The
DRM driver exposes different values for the panel's width, height and
refresh rate, and the DRM driver fails a FBIOPUT_VSCREENINFO syscall
with yres_virtual greater than the maximum supported value instead
of letting the syscall succeed and setting yres_virtual based on yres.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200929195344.2219796-1-pcc@google.com

1 files changed, 290 insertions, 0 deletions

diff --git a/include/linux/amba/clcd.h b/include/linux/amba/clcd.h
new file mode 100644
index 000000000000..b6e0cbeaf533
--- /dev/null
+++ b/include/linux/amba/clcd.h
@@ -0,0 +1,290 @@
+/*
+ * linux/include/asm-arm/hardware/amba_clcd.h -- Integrator LCD panel.
+ *
+ * David A Rusling
+ *
+ * Copyright (C) 2001 ARM Limited
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+#include <linux/fb.h>
+#include <linux/amba/clcd-regs.h>
+
+enum {
+	/* individual formats */
+	CLCD_CAP_RGB444		= (1 << 0),
+	CLCD_CAP_RGB5551	= (1 << 1),
+	CLCD_CAP_RGB565		= (1 << 2),
+	CLCD_CAP_RGB888		= (1 << 3),
+	CLCD_CAP_BGR444		= (1 << 4),
+	CLCD_CAP_BGR5551	= (1 << 5),
+	CLCD_CAP_BGR565		= (1 << 6),
+	CLCD_CAP_BGR888		= (1 << 7),
+
+	/* connection layouts */
+	CLCD_CAP_444		= CLCD_CAP_RGB444 | CLCD_CAP_BGR444,
+	CLCD_CAP_5551		= CLCD_CAP_RGB5551 | CLCD_CAP_BGR5551,
+	CLCD_CAP_565		= CLCD_CAP_RGB565 | CLCD_CAP_BGR565,
+	CLCD_CAP_888		= CLCD_CAP_RGB888 | CLCD_CAP_BGR888,
+
+	/* red/blue ordering */
+	CLCD_CAP_RGB		= CLCD_CAP_RGB444 | CLCD_CAP_RGB5551 |
+				  CLCD_CAP_RGB565 | CLCD_CAP_RGB888,
+	CLCD_CAP_BGR		= CLCD_CAP_BGR444 | CLCD_CAP_BGR5551 |
+				  CLCD_CAP_BGR565 | CLCD_CAP_BGR888,
+
+	CLCD_CAP_ALL		= CLCD_CAP_BGR | CLCD_CAP_RGB,
+};
+
+struct backlight_device;
+
+struct clcd_panel {
+	struct fb_videomode	mode;
+	signed short		width;	/* width in mm */
+	signed short		height;	/* height in mm */
+	u32			tim2;
+	u32			tim3;
+	u32			cntl;
+	u32			caps;
+	unsigned int		bpp:8,
+				fixedtimings:1,
+				grayscale:1;
+	unsigned int		connector;
+	struct backlight_device	*backlight;
+	/*
+	 * If the B/R lines are switched between the CLCD
+	 * and the panel we need to know this and not try to
+	 * compensate with the BGR bit in the control register.
+	 */
+	bool			bgr_connection;
+};
+
+struct clcd_regs {
+	u32			tim0;
+	u32			tim1;
+	u32			tim2;
+	u32			tim3;
+	u32			cntl;
+	unsigned long		pixclock;
+};
+
+struct clcd_fb;
+
+/*
+ * the board-type specific routines
+ */
+struct clcd_board {
+	const char *name;
+
+	/*
+	 * Optional.  Hardware capability flags.
+	 */
+	u32	caps;
+
+	/*
+	 * Optional.  Check whether the var structure is acceptable
+	 * for this display.
+	 */
+	int	(*check)(struct clcd_fb *fb, struct fb_var_screeninfo *var);
+
+	/*
+	 * Compulsory.  Decode fb->fb.var into regs->*.  In the case of
+	 * fixed timing, set regs->* to the register values required.
+	 */
+	void	(*decode)(struct clcd_fb *fb, struct clcd_regs *regs);
+
+	/*
+	 * Optional.  Disable any extra display hardware.
+	 */
+	void	(*disable)(struct clcd_fb *);
+
+	/*
+	 * Optional.  Enable any extra display hardware.
+	 */
+	void	(*enable)(struct clcd_fb *);
+
+	/*
+	 * Setup platform specific parts of CLCD driver
+	 */
+	int	(*setup)(struct clcd_fb *);
+
+	/*
+	 * mmap the framebuffer memory
+	 */
+	int	(*mmap)(struct clcd_fb *, struct vm_area_struct *);
+
+	/*
+	 * Remove platform specific parts of CLCD driver
+	 */
+	void	(*remove)(struct clcd_fb *);
+};
+
+struct amba_device;
+struct clk;
+
+/* this data structure describes each frame buffer device we find */
+struct clcd_fb {
+	struct fb_info		fb;
+	struct amba_device	*dev;
+	struct clk		*clk;
+	struct clcd_panel	*panel;
+	struct clcd_board	*board;
+	void			*board_data;
+	void __iomem		*regs;
+	u16			off_ienb;
+	u16			off_cntl;
+	u32			clcd_cntl;
+	u32			cmap[16];
+	bool			clk_enabled;
+};
+
+static inline void clcdfb_decode(struct clcd_fb *fb, struct clcd_regs *regs)
+{
+	struct fb_var_screeninfo *var = &fb->fb.var;
+	u32 val, cpl;
+
+	/*
+	 * Program the CLCD controller registers and start the CLCD
+	 */
+	val = ((var->xres / 16) - 1) << 2;
+	val |= (var->hsync_len - 1) << 8;
+	val |= (var->right_margin - 1) << 16;
+	val |= (var->left_margin - 1) << 24;
+	regs->tim0 = val;
+
+	val = var->yres;
+	if (fb->panel->cntl & CNTL_LCDDUAL)
+		val /= 2;
+	val -= 1;
+	val |= (var->vsync_len - 1) << 10;
+	val |= var->lower_margin << 16;
+	val |= var->upper_margin << 24;
+	regs->tim1 = val;
+
+	val = fb->panel->tim2;
+	val |= var->sync & FB_SYNC_HOR_HIGH_ACT  ? 0 : TIM2_IHS;
+	val |= var->sync & FB_SYNC_VERT_HIGH_ACT ? 0 : TIM2_IVS;
+
+	cpl = var->xres_virtual;
+	if (fb->panel->cntl & CNTL_LCDTFT)	  /* TFT */
+		/* / 1 */;
+	else if (!var->grayscale)		  /* STN color */
+		cpl = cpl * 8 / 3;
+	else if (fb->panel->cntl & CNTL_LCDMONO8) /* STN monochrome, 8bit */
+		cpl /= 8;
+	else					  /* STN monochrome, 4bit */
+		cpl /= 4;
+
+	regs->tim2 = val | ((cpl - 1) << 16);
+
+	regs->tim3 = fb->panel->tim3;
+
+	val = fb->panel->cntl;
+	if (var->grayscale)
+		val |= CNTL_LCDBW;
+
+	if (fb->panel->caps && fb->board->caps && var->bits_per_pixel >= 16) {
+		/*
+		 * if board and panel supply capabilities, we can support
+		 * changing BGR/RGB depending on supplied parameters. Here
+		 * we switch to what the framebuffer is providing if need
+		 * be, so if the framebuffer is BGR but the display connection
+		 * is RGB (first case) we switch it around. Vice versa mutatis
+		 * mutandis if the framebuffer is RGB but the display connection
+		 * is BGR, we flip it around.
+		 */
+		if (var->red.offset == 0)
+			val &= ~CNTL_BGR;
+		else
+			val |= CNTL_BGR;
+		if (fb->panel->bgr_connection)
+			val ^= CNTL_BGR;
+	}
+
+	switch (var->bits_per_pixel) {
+	case 1:
+		val |= CNTL_LCDBPP1;
+		break;
+	case 2:
+		val |= CNTL_LCDBPP2;
+		break;
+	case 4:
+		val |= CNTL_LCDBPP4;
+		break;
+	case 8:
+		val |= CNTL_LCDBPP8;
+		break;
+	case 16:
+		/*
+		 * PL110 cannot choose between 5551 and 565 modes in its
+		 * control register.  It is possible to use 565 with
+		 * custom external wiring.
+		 */
+		if (amba_part(fb->dev) == 0x110 ||
+		    var->green.length == 5)
+			val |= CNTL_LCDBPP16;
+		else if (var->green.length == 6)
+			val |= CNTL_LCDBPP16_565;
+		else
+			val |= CNTL_LCDBPP16_444;
+		break;
+	case 32:
+		val |= CNTL_LCDBPP24;
+		break;
+	}
+
+	regs->cntl = val;
+	regs->pixclock = var->pixclock;
+}
+
+static inline int clcdfb_check(struct clcd_fb *fb, struct fb_var_screeninfo *var)
+{
+	var->xres_virtual = var->xres = (var->xres + 15) & ~15;
+	var->yres_virtual = var->yres = (var->yres + 1) & ~1;
+
+#define CHECK(e,l,h) (var->e < l || var->e > h)
+	if (CHECK(right_margin, (5+1), 256) ||	/* back porch */
+	    CHECK(left_margin, (5+1), 256) ||	/* front porch */
+	    CHECK(hsync_len, (5+1), 256) ||
+	    var->xres > 4096 ||
+	    var->lower_margin > 255 ||		/* back porch */
+	    var->upper_margin > 255 ||		/* front porch */
+	    var->vsync_len > 32 ||
+	    var->yres > 1024)
+		return -EINVAL;
+#undef CHECK
+
+	/* single panel mode: PCD = max(PCD, 1) */
+	/* dual panel mode: PCD = max(PCD, 5) */
+
+	/*
+	 * You can't change the grayscale setting, and
+	 * we can only do non-interlaced video.
+	 */
+	if (var->grayscale != fb->fb.var.grayscale ||
+	    (var->vmode & FB_VMODE_MASK) != FB_VMODE_NONINTERLACED)
+		return -EINVAL;
+
+#define CHECK(e) (var->e != fb->fb.var.e)
+	if (fb->panel->fixedtimings &&
+	    (CHECK(xres)		||
+	     CHECK(yres)		||
+	     CHECK(bits_per_pixel)	||
+	     CHECK(pixclock)		||
+	     CHECK(left_margin)		||
+	     CHECK(right_margin)	||
+	     CHECK(upper_margin)	||
+	     CHECK(lower_margin)	||
+	     CHECK(hsync_len)		||
+	     CHECK(vsync_len)		||
+	     CHECK(sync)))
+		return -EINVAL;
+#undef CHECK
+
+	var->nonstd = 0;
+	var->accel_flags = 0;
+
+	return 0;
+}