glamo_fb: Implement screen blanking

This patch implements fb_blank() for the glamo-fb driver, which switches off
the pixel clock (DCLK) for power saving.

We currently delay the actual pixel clock switch until we enter
FB_BLANK_POWERDOWN, since the backlight fade is slow and we don't want the
user to see artefacts on the screen while the backlight is fading out.

So since the X server first sends FB_BLANK_{V,H}SYNC_SUSPEND, we start the
backlight fade here, and only once we get FB_BLANK_POWERDOWN the pixel clock is
disabled.

There are no measurements yet, but the power savings should be double, since
there is no longer any  generation of the high-frequency LCM signals, and
there are no video-related SDRAM accesses anymore.

Signed-off-by: Harald Welte <laforge@openmoko.org>

1 files changed, 28 insertions, 1 deletions

diff --git a/drivers/mfd/glamo/glamo-fb.c b/drivers/mfd/glamo/glamo-fb.c
index 0bc6a1be63f..1ae933e9a3e 100644
--- a/drivers/mfd/glamo/glamo-fb.c
+++ b/drivers/mfd/glamo/glamo-fb.c
@@ -422,7 +422,34 @@ static int glamofb_set_par(struct fb_info *info)
 
 static int glamofb_blank(int blank_mode, struct fb_info *info)
 {
-	/* FIXME */
+	struct glamofb_handle *gfb = info->par;
+	struct glamo_core *gcore = gfb->mach_info->glamo;
+
+	dev_dbg(gfb->dev, "glamofb_blank(%u)\n", blank_mode);
+
+	switch (blank_mode) {
+	case FB_BLANK_VSYNC_SUSPEND:
+	case FB_BLANK_HSYNC_SUSPEND:
+		/* FIXME: add pdata hook/flag to indicate whether
+		 * we should already switch off pixel clock here */
+		break;
+	case FB_BLANK_POWERDOWN:
+		/* disable the pixel clock */
+		glamo_engine_clkreg_set(gcore, GLAMO_ENGINE_LCD,
+					GLAMO_CLOCK_LCD_EN_DCLK, 0);
+		break;
+	case FB_BLANK_UNBLANK:
+	case FB_BLANK_NORMAL:
+		/* enable the pixel clock */
+		glamo_engine_clkreg_set(gcore, GLAMO_ENGINE_LCD,
+					GLAMO_CLOCK_LCD_EN_DCLK,
+					GLAMO_CLOCK_LCD_EN_DCLK);
+		break;
+	}
+
+	/* FIXME: once we have proper clock management in glamo-core,
+	 * we can determine if other units need MCLK1 or the PLL, and
+	 * disable it if not used. */
 	return 0;
 }