code: plan9front

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imx8/lcd: disable the bridge output on blank

Disabling LCDIF often produces flickering output at the top
of the LCD panel (timings going wrong?). Instead, just disable the
output on the bridge, which is much simpler, doesn't seem to cause
any issues, and saves enough power just as well.

--- a/sys/src/9/imx8/lcd.c

+++ b/sys/src/9/imx8/lcd.c

@@ -356,11 +356,6 @@

 static u32int *lcdif = (u32int*)(VIRTIO + 0x320000);

-static struct {

-	Lock;

-	int blank;

-}lcdifirq;

-

 /* shift and mask */

 static u32int

 sm(u32int v, u32int m)

@@ -469,8 +464,7 @@

 	/* enable underflow recovery to fix image shift */

 	wr(lcdif, LCDIF_CTRL1,

 		sm(7, CTRL1_BYTE_PACKING_FORMAT) |

-		CTRL1_RECOVER_ON_UNDERFLOW |

-		CTRL1_CUR_FRAME_DONE_IRQ_EN);

+		CTRL1_RECOVER_ON_UNDERFLOW);

 	wr(lcdif, LCDIF_CTRL,

 		CTRL_BYPASS_COUNT |

@@ -834,35 +828,15 @@

 	gpioout(GPIO_PIN(1, 10), 1);

 }

-static void

-lcdifinterrupt(Ureg *, void *)

-{

-	wr(lcdif, LCDIF_CTRL1_CLR, CTRL1_CUR_FRAME_DONE_IRQ);

-	ilock(&lcdifirq);

-	if(lcdifirq.blank){

-		/* turn off dotclk */

-		wr(lcdif, LCDIF_CTRL_CLR, CTRL_DOTCLK_MODE);

-		/* wait for the fifo to empty */

-		while(rr(lcdif, LCDIF_CTRL) & CTRL_RUN)

-			;

-		lcdifirq.blank = 0;

-	}

-	iunlock(&lcdifirq);

-}

-

 void

 blankscreen(int blank)

 {

-	ilock(&lcdifirq);

-	lcdifirq.blank = blank;

-	if(blank == 0) /* restart lcdif */

-		wr(lcdif, LCDIF_CTRL_SET, CTRL_DOTCLK_MODE | CTRL_RUN);

-	iunlock(&lcdifirq);

-

-	/* toggle panel backlight */

+	/* panel backlight */

 	gpioout(GPIO_PIN(1, 10), blank == 0);

-	/* toggle PWM2 */

+	/* PWM2 */

 	mr(pwm2, PWMCR, (blank == 0)*CR_EN, CR_EN);

+	/* bridge output */

+	i2cwritebyte(i2cdev(i2cbus("i2c4"), 0x2c), 0x5a, blank == 0 ? 0x0d : 0x05);

 }

 static void

@@ -921,8 +895,6 @@

 	setclkgate("sim_display.mainclk", 1);

 	lcdifreset();

-

-	intrenable(IRQlcdif, lcdifinterrupt, nil, BUSUNKNOWN, "lcdif");

 	setclkrate("mipi.core", "system_pll1_div3", 266*Mhz);

 	setclkrate("mipi.CLKREF", "system_pll2_clk", 25*Mhz);