shithub: riscv

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ref: a0048b5c193943708c00dbbd0f5e9fed8c71e515
parent: a194f52c9377e010c31612d6484cbd43df6d5e24
author: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se>
date: Fri Sep 2 12:12:04 EDT 2022 

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);