samsung-a5: fb_convert_to_xrgb8888 causes data fault

[samcday]

When booting U-Boot with lk2nd.pass-simplefb=uboot command line, the following exception is triggered in lk2nd:

[670] simplefb: switching to xrgb888 because u-boot can't do 24
[720] data abort
[720] translation fault on write
[720] DFAR 0x8e300000 (fault address)
[720] DFSR 0x805 (fault status register)
[730] data abort, halting
[730] r0  0x8e300000 r1  0x90300020 r2  0x00083fc0 r3  0x1e000000
[740] r4  0xbf000000 r5  0x00000000 r6  0x00000000 r7  0x00000000
[740] r8  0x33000000 r9  0x01000000 r10 0x00000000 r11 0x00000000
[750] r12 0x01a15000 usp 0x00000000 ulr 0x00000000 pc  0x8f6213a0
[750] spsr 0x20000153
[760]  fiq r13 0x8f649000 r14 0x864001b8
[760]  irq r13 0x8f655260 r14 0x8f60ca28
[760] *svc r13 0x8f684d00 r14 0x8f62b334
[770]  und r13 0x8f649000 r14 0xffbce774
[770]  sys r13 0x00000000 r14 0x00000000
[770] bottom of stack at 0x8f684d00:
0x8f684d00: 8f67ee14 81e00000 8f644100 8f644140 |..g......Ad..Ad.|
0x8f684d10: 00000000 00000000 8e000000 8f67ee14 |..............g.|
0x8f684d20: 90000000 8f62b334 8f68dd84 4b3f9c01 |......b...h....K|
0x8f684d30: 8f63eb04 00000001 8f68dd84 8f62afdc |..c.......h...b.|
0x8f684d40: 0000c704 4b3f9c01 0000c6e8 81e00000 |.......K........|
0x8f684d50: 81e0c724 6f6f6275 81e00074 ffffffff |....uboot.......|
0x8f684d60: 00000015 4b3f9c01 8f63af89 8f63af81 |.......K..c...c.|
0x8f684d70: 8f63af89 00001d64 81e00000 8f623200 |..c.d.........b.|

$ addr2line -e build-lk2nd-msm8916/lk 0x8f6213a0
/var/home/sam/src/lk2nd/lib/libc/string/arch/arm/memcpy.S:87

Manually commenting out mdp_set_xrgb8888 and instead using mdp_set_rgb565 does work.

[exkc]

j5x might have the same issue. uboot initially failed to boot due to #3 . i worked around that by dumping all the file in thirdstage.ext2 into system. After that it started to bootloop thus i tried do smailer thing as above . it stoped boot looping after that but uboot console didnt show up on the sceen and i dont have other way verify uboot boot

[TravMurav]

Hi! At some point I've updated lk2nd to allow framebuffer relocation, but unfortunately I didn't have time to update this repo yet to build latest versions of lk2nd and u-boot yet. I believe you should be able to build it with latest lk2nd and update cmdline with new value:

gen-uboot-img/extlinux/extlinux.conf

Line 7 in f478d92

append lk2nd.pass-ramoops=zap lk2nd.pass-simplefb=uboot

should be changed to use lk2nd.pass-simplefb=xrgb8888,relocate

[exkc]

alr i builded the lastest uboot and latest main branches of lk2nd with patches from rebase/hl (bc of qhypstub (see msm8916-mainline/lk2nd#414) ) and it booted pm os that on the sdcard but the screen went black when the phone is in uboot ( linux did trun the screen on after uboot booted linux via efi)

[samcday]

I confirmed today that lk2nd 20.0 is still hitting the same data abort when trying to relocate the framebuffer in xrgb8888 mode.

I can get a working simplefb in U-Boot with the rgb565 pixel format (albeit with framebuffer corruption of the Samsung boot logo) on my samsung-a5, however I needed to apply the following patch to lk2nd:

diff --git a/lk2nd/display/simplefb.c b/lk2nd/display/simplefb.c
index b724d527d..ab07aa201 100644
--- a/lk2nd/display/simplefb.c
+++ b/lk2nd/display/simplefb.c
@@ -28,9 +28,7 @@ static int lk2nd_simplefb_dt_update(void *dtb, const char *cmdline,
 	int ret, resmem_offset, chosen_offset, offset;
 	uint32_t mem_ph, fb_size;
 	char tmp[32], args[16];
-#if WITH_LK2ND_DISPLAY_CONT_SPLASH
 	void *rel_base;
-#endif
 
 	if (!fb)
 		return 0;
@@ -46,6 +44,8 @@ static int lk2nd_simplefb_dt_update(void *dtb, const char *cmdline,
 		dprintf(INFO, "simplefb: Enabling autorefresh\n");
 		mdp_enable_autorefresh(fb);
 	}
+#endif
+
 
 	if (strstr(args, "relocate")) {
 		rel_base = target_get_scratch_address()
@@ -60,7 +60,6 @@ static int lk2nd_simplefb_dt_update(void *dtb, const char *cmdline,
 		mdp_set_rgb565(fb);
 	else if (strstr(args, "xrgb8888"))
 		mdp_set_xrgb8888(fb);
-#endif
 
 	fb_size = fb->stride * fb->bpp/8 * fb->height;

It doesn't seem correct to me that the relocation and pixel-format changes are only allowed for displays with continuous splash, but I don't claim to understand that code very well 😅 I'm happy to raise a downstream issue in lk2nd if you think it's appropriate.

[TravMurav]

It doesn't seem correct to me that the relocation and pixel-format changes are only allowed for displays with continuous splash

I've looked at it more today and noticed that the code is slightly broken. cont-splash is the state used by pretty much all devices in lk2nd (compared to lk1st where lk2nd initializes the display itself so it's correct to guard this code as the mdp reconfiguration functions are implemented as part of cont-splash and not the caf display driver)

I've applied few fixes in lk2nd to make this work correctly, which might fix the data abort issue as well, since there was a bug in the argument parsing there too...