Fix low-res screens on T60 (patch from Arthur Heymans)

1 files changed, 174 insertions, 0 deletions

diff --git a/resources/libreboot/patch/coreboot/2a3434757ef425dbdfedf1fc69e1a033a6e7310d/grub/t60/0003-i945-gma.c-use-latest-linux-code-to-calculate-diviso.patch b/resources/libreboot/patch/coreboot/2a3434757ef425dbdfedf1fc69e1a033a6e7310d/grub/t60/0003-i945-gma.c-use-latest-linux-code-to-calculate-diviso.patch
new file mode 100644
index 00000000..86bd6cb0
--- /dev/null
+++ b/resources/libreboot/patch/coreboot/2a3434757ef425dbdfedf1fc69e1a033a6e7310d/grub/t60/0003-i945-gma.c-use-latest-linux-code-to-calculate-diviso.patch
@@ -0,0 +1,174 @@
+From 34f8cdbc30f1fdf4700c73aad26e0fc159af70ab Mon Sep 17 00:00:00 2001
+From: Arthur Heymans <arthur@aheymans.xyz>
+Date: Fri, 2 Sep 2016 22:35:32 +0200
+Subject: [PATCH] i945/gma.c use latest linux code to calculate divisors.
+
+The code to compute n, m1, m2, p1 divisors is not correct in coreboot and
+on some targets hits a working mode at lower refresh rate, which is why
+display is working on some targets.
+This patch also fixes reference frequency.
+
+This patch reuses linux code to correctly compute divisors.
+
+The result is that some previously not working displays (Lenovo T60 with
+1024x786, 1400x1050, 2048x1536)
+
+TESTED on T60 with 1024x786.
+
+Change-Id: I2c7f3bb0024ac005029eaebe3ecdc70c38ac777e
+Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
+---
+ src/northbridge/intel/i945/gma.c | 82 +++++++++++++++++++---------------------
+ 1 file changed, 38 insertions(+), 44 deletions(-)
+
+diff --git a/src/northbridge/intel/i945/gma.c b/src/northbridge/intel/i945/gma.c
+index 02caa0a..3f0b5b4 100644
+--- a/src/northbridge/intel/i945/gma.c
++++ b/src/northbridge/intel/i945/gma.c
+@@ -26,6 +26,8 @@
+ #include <string.h>
+ #include <pc80/vga.h>
+ #include <pc80/vga_io.h>
++#include <commonlib/helpers.h>
++
+ 
+ #include "i945.h"
+ #include "chip.h"
+@@ -43,7 +45,7 @@
+ #define PGETBL_CTL	0x2020
+ #define PGETBL_ENABLED	0x00000001
+ 
+-#define BASE_FREQUENCY 120000
++#define BASE_FREQUENCY 100000
+ 
+ #if CONFIG_MAINBOARD_DO_NATIVE_VGA_INIT
+ 
+@@ -85,10 +87,10 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 	u8 edid_data[128];
+ 	unsigned long temp;
+ 	int hpolarity, vpolarity;
+-	u32 candp1, candn;
+-	u32 best_delta = 0xffffffff;
++	u32 smallest_err = 0xffffffff;
+ 	u32 target_frequency;
+ 	u32 pixel_p1 = 1;
++	u32 pixel_p2;
+ 	u32 pixel_n = 1;
+ 	u32 pixel_m1 = 1;
+ 	u32 pixel_m2 = 1;
+@@ -158,43 +160,37 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 	write32(pmmio + PORT_HOTPLUG_EN, conf->gpu_hotplug);
+ 	write32(pmmio + INSTPM, 0x08000000 | INSTPM_AGPBUSY_DIS);
+ 
+-	target_frequency = mode->lvds_dual_channel ? mode->pixel_clock
+-		: (2 * mode->pixel_clock);
+-
+-	/* Find suitable divisors.  */
+-	for (candp1 = 1; candp1 <= 8; candp1++) {
+-		for (candn = 5; candn <= 10; candn++) {
+-			u32 cur_frequency;
+-			u32 m; /* 77 - 131.  */
+-			u32 denom; /* 35 - 560.  */
+-			u32 current_delta;
+-
+-			denom = candn * candp1 * 7;
+-			/* Doesnt overflow for up to
+-			   5000000 kHz = 5 GHz.  */
+-			m = (target_frequency * denom
+-			     + BASE_FREQUENCY / 2) / BASE_FREQUENCY;
+-
+-			if (m < 77 || m > 131)
+-				continue;
+-
+-			cur_frequency = (BASE_FREQUENCY * m) / denom;
+-			if (target_frequency > cur_frequency)
+-				current_delta = target_frequency - cur_frequency;
+-			else
+-				current_delta = cur_frequency - target_frequency;
+-
+-			if (best_delta > current_delta) {
+-				best_delta = current_delta;
+-				pixel_n = candn;
+-				pixel_p1 = candp1;
+-				pixel_m2 = ((m + 3) % 5) + 7;
+-				pixel_m1 = (m - pixel_m2) / 5;
++	pixel_p2 = mode->lvds_dual_channel ? 7 : 14;
++	target_frequency = mode->pixel_clock;
++
++	/* Find suitable divisors, m1, m2, p1, n.  */
++	/* refclock * (5 * (m1 + 2) + (m1 + 2)) / (n + 2) / p1 / p2 */
++	/* should be closest to target frequency as possible */
++	u32 candn, candm1, candm2, candp1;
++	for (candm1 = 8; candm1 <= 18; candm1++) {
++		for (candm2 = 3; candm2 <= 7; candm2++) {
++			for (candn = 1; candn <= 6; candn++) {
++				for (candp1 = 1; candp1 <= 8; candp1++) {
++					u32 m = 5 * (candm1 + 2) + (candm2 + 2);
++					u32 p = candp1 * pixel_p2;
++					u32 vco = DIV_ROUND_CLOSEST(BASE_FREQUENCY * m, candn + 2);
++					u32 dot = DIV_ROUND_CLOSEST(vco, p);
++					u32 this_err = ABS(dot - target_frequency);
++					if ((m < 70) || (m > 120))
++						continue;
++					if (this_err < smallest_err) {
++						smallest_err = this_err;
++						pixel_n = candn;
++						pixel_m1 = candm1;
++						pixel_m2 = candm2;
++						pixel_p1 = candp1;
++					}
++				}
+ 			}
+ 		}
+ 	}
+ 
+-	if (best_delta == 0xffffffff) {
++	if (smallest_err == 0xffffffff) {
+ 		printk (BIOS_ERR, "Couldn't find GFX clock divisors\n");
+ 		return -1;
+ 	}
+@@ -216,8 +212,8 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 	printk(BIOS_DEBUG, "Pixel N=%d, M1=%d, M2=%d, P1=%d\n",
+ 	       pixel_n, pixel_m1, pixel_m2, pixel_p1);
+ 	printk(BIOS_DEBUG, "Pixel clock %d kHz\n",
+-	       BASE_FREQUENCY * (5 * pixel_m1 + pixel_m2) / pixel_n
+-	       / (pixel_p1 * 7));
++	       BASE_FREQUENCY * (5 * (pixel_m1 + 2) + (pixel_m2 + 2)) /
++	       (pixel_n + 2) / (pixel_p1 * pixel_p2));
+ 
+ #if !IS_ENABLED(CONFIG_FRAMEBUFFER_KEEP_VESA_MODE)
+ 	write32(pmmio + PF_WIN_SZ(0), vactive | (hactive << 16));
+@@ -242,8 +238,8 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 	write32(pmmio + PP_CONTROL, PANEL_UNLOCK_REGS
+ 		| (read32(pmmio + PP_CONTROL) & ~PANEL_UNLOCK_MASK));
+ 	write32(pmmio + FP0(1),
+-		((pixel_n - 2) << 16)
+-		| ((pixel_m1 - 2) << 8) | pixel_m2);
++		(pixel_n << 16)
++		| (pixel_m1 << 8) | pixel_m2);
+ 	write32(pmmio + DPLL(1),
+ 		DPLL_VGA_MODE_DIS |
+ 		DPLL_VCO_ENABLE | DPLLB_MODE_LVDS
+@@ -252,8 +248,7 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 		| (conf->gpu_lvds_use_spread_spectrum_clock
+ 		   ? DPLL_INTEGRATED_CLOCK_VLV | DPLL_INTEGRATED_CRI_CLK_VLV
+ 		   : 0)
+-		| (pixel_p1 << 16)
+-		| (pixel_p1));
++		| (0x10000 << pixel_p1));
+ 	mdelay(1);
+ 	write32(pmmio + DPLL(1),
+ 		DPLL_VGA_MODE_DIS |
+@@ -261,8 +256,7 @@ static int intel_gma_init(struct northbridge_intel_i945_config *conf,
+ 		| (mode->lvds_dual_channel ? DPLLB_LVDS_P2_CLOCK_DIV_7
+ 		   : DPLLB_LVDS_P2_CLOCK_DIV_14)
+ 		| ((conf->gpu_lvds_use_spread_spectrum_clock ? 3 : 0) << 13)
+-		| (pixel_p1 << 16)
+-		| (pixel_p1));
++		| (0x10000 << pixel_p1));
+ 	mdelay(1);
+ 	write32(pmmio + HTOTAL(1),
+ 		((hactive + right_border + hblank - 1) << 16)
+-- 
+2.9.3
+