shithub: plan9front

Download patch

ref: c5cf9b3e26033272c5f57b9a860c335e63786045
parent: 940e3165d31370871e66e0ae2cce13f010cb26ba
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Sun Jul 3 12:13:19 EDT 2022

imx8: qos magic to avoid interference between pcie and lcdif

when writing to the nvme ssd, the screen can glitch out.

found this in linux lcdif driver (mxcfb) that appears to
resolve the issue.

the QoSc registers are all completely undocumented tho :-(

--- a/sys/src/9/imx8/pciimx.c	Sun Jul  3 08:10:27 2022
+++ b/sys/src/9/imx8/pciimx.c	Sun Jul  3 12:13:19 2022
@@ -410,6 +410,34 @@
 	rootinit(&ctlrs[1]);
 }
 
+/* undocumented magic to avoid interference between lcdif and pcie */
+static void
+qosmagic(void)
+{
+	static u32int *qosc = (u32int*)(VIRTIO + 0x7f0000);
+
+	/* unlock */
+	qosc[0x0000/4] = 0x0;
+	qosc[0x0000/4] = 0x1;
+	qosc[0x0060/4] = 0x0;
+
+	/* pci1 */
+	qosc[0x1000/4] = 0x0;
+	qosc[0x1000/4] = 0x1;
+	qosc[0x1050/4] = 0x01010100;
+	qosc[0x1060/4] = 0x01010100;
+	qosc[0x1070/4] = 0x01010100;
+	qosc[0x1000/4] = 0x1;
+
+	/* pcie2 */
+	qosc[0x2000/4] = 0x0;
+	qosc[0x2000/4] = 0x1;
+	qosc[0x2050/4] = 0x01010100;
+	qosc[0x2060/4] = 0x01010100;
+	qosc[0x2070/4] = 0x01010100;
+	qosc[0x2000/4] = 0x1;
+}
+
 enum {
 	SRC_PCIEPHY_RCR		= 0x2C/4,
 	SRC_PCIE2_RCR		= 0x48/4,
@@ -494,4 +522,6 @@
 	resetc[SRC_PCIE2_RCR] &= ~(PCIE_BTN | PCIE_G_RST);
 
 	pcicfginit();
+
+	qosmagic();
 }