intelfb: fix setting of active pipe with LVDS displays

The intelfb driver sets color map depending on currently active pipe.
However, if an LVDS display is attached (like in laptop) the active pipe
variable is never set. The default value is PIPE_A and can be wrong. Set
up the pipe variable during driver initialization after hardware state was
read.

Also, the detection of the active display (and hence the pipe) is wrong.
The pipes are assigned to so called planes. Both pipes are always enabled
on my laptop but only one plane is enabled (the plane A for the CRT or the
plane B for the LVDS). Change active pipe detection code to take into
account a status of the plane assigned to each pipe.

The problem is visible in the 8 bpp mode if colors above 15 are used. The
first 16 color entries are displayed correctly.

The graphics chip description is here (G45 vol. 3):
http://intellinuxgraphics.org/documentation.html

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=13285

Signed-off-by: Krzysztof Helt <[e-mail]>
Cc: Michal Suchanek <[e-mail]>
Cc: Dean Menezes <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/intelfb/intelfbdrv.c

···
 	if (bailearly == 18)
 		bailout(dinfo);
 
+	/* read active pipe */
+	dinfo->pipe = intelfbhw_active_pipe(&dinfo->save_state);
+
 	/* Cursor initialisation */
 	if (dinfo->hwcursor) {
 		intelfbhw_cursor_init(dinfo);

drivers/video/intelfb/intelfbhw.c

···
 }
 
 
+/* Check which pipe is connected to an active display plane. */
+int intelfbhw_active_pipe(const struct intelfb_hwstate *hw)
+{
+	int pipe = -1;
+
+	/* keep old default behaviour - prefer PIPE_A */
+	if (hw->disp_b_ctrl & DISPPLANE_PLANE_ENABLE) {
+		pipe = (hw->disp_b_ctrl >> DISPPLANE_SEL_PIPE_SHIFT);
+		pipe &= PIPE_MASK;
+		if (unlikely(pipe == PIPE_A))
+			return PIPE_A;
+	}
+	if (hw->disp_a_ctrl & DISPPLANE_PLANE_ENABLE) {
+		pipe = (hw->disp_a_ctrl >> DISPPLANE_SEL_PIPE_SHIFT);
+		pipe &= PIPE_MASK;
+		if (likely(pipe == PIPE_A))
+			return PIPE_A;
+	}
+	/* Impossible that no pipe is selected - return PIPE_A */
+	WARN_ON(pipe == -1);
+	if (unlikely(pipe == -1))
+		pipe = PIPE_A;
+
+	return pipe;
+}
+
 void intelfbhw_setcolreg(struct intelfb_info *dinfo, unsigned regno,
 			 unsigned red, unsigned green, unsigned blue,
 			 unsigned transp)
···
 			 struct intelfb_hwstate *hw,
 			 struct fb_var_screeninfo *var)
 {
-	int pipe = PIPE_A;
+	int pipe = intelfbhw_active_pipe(hw);
 	u32 *dpll, *fp0, *fp1;
 	u32 m1, m2, n, p1, p2, clock_target, clock;
 	u32 hsync_start, hsync_end, hblank_start, hblank_end, htotal, hactive;
···
 
 	/* Disable VGA */
 	hw->vgacntrl |= VGA_DISABLE;
-
-	/* Check whether pipe A or pipe B is enabled. */
-	if (hw->pipe_a_conf & PIPECONF_ENABLE)
-		pipe = PIPE_A;
-	else if (hw->pipe_b_conf & PIPECONF_ENABLE)
-		pipe = PIPE_B;
 
 	/* Set which pipe's registers will be set. */
 	if (pipe == PIPE_B) {
···
 int intelfbhw_program_mode(struct intelfb_info *dinfo,
 			   const struct intelfb_hwstate *hw, int blank)
 {
-	int pipe = PIPE_A;
 	u32 tmp;
 	const u32 *dpll, *fp0, *fp1, *pipe_conf;
 	const u32 *hs, *ht, *hb, *vs, *vt, *vb, *ss;
···
 	u32 src_size_reg;
 	u32 count, tmp_val[3];
 
-	/* Assume single pipe, display plane A, analog CRT. */
+	/* Assume single pipe */
 
 #if VERBOSE > 0
 	DBG_MSG("intelfbhw_program_mode\n");
···
 	tmp |= VGA_DISABLE;
 	OUTREG(VGACNTRL, tmp);
 
-	/* Check whether pipe A or pipe B is enabled. */
-	if (hw->pipe_a_conf & PIPECONF_ENABLE)
-		pipe = PIPE_A;
-	else if (hw->pipe_b_conf & PIPECONF_ENABLE)
-		pipe = PIPE_B;
+	dinfo->pipe = intelfbhw_active_pipe(hw);
 
-	dinfo->pipe = pipe;
-
-	if (pipe == PIPE_B) {
+	if (dinfo->pipe == PIPE_B) {
 		dpll = &hw->dpll_b;
 		fp0 = &hw->fpb0;
 		fp1 = &hw->fpb1;

drivers/video/intelfb/intelfbhw.h

···
 extern int intelfbhw_enable_irq(struct intelfb_info *dinfo);
 extern void intelfbhw_disable_irq(struct intelfb_info *dinfo);
 extern int intelfbhw_wait_for_vsync(struct intelfb_info *dinfo, u32 pipe);
+extern int intelfbhw_active_pipe(const struct intelfb_hwstate *hw);
 
 #endif /* _INTELFBHW_H */