While investigating a lockup at startup on Powerbook 3400C, it was identified that the fbdev driver generates alignment exception at startup:
--- interrupt: 600 at memset+0x60/0xc0 NIP: c0021414 LR: c03fc49c CTR: 00007fff REGS: ca021c10 TRAP: 0600 Tainted: G W (5.14.2-pmac-00727-g12a41fa69492) MSR: 00009032 <EE,ME,IR,DR,RI> CR: 44008442 XER: 20000100 DAR: cab80020 DSISR: 00017c07 GPR00: 00000007 ca021cd0 c14412e0 cab80000 00000000 00100000 cab8001c 00000004 GPR08: 00100000 00007fff 00000000 00000000 84008442 00000000 c0006fb4 00000000 GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00100000 GPR24: 00000000 81800000 00000320 c15fa400 c14d1878 00000000 c14d1800 c094e19c NIP [c0021414] memset+0x60/0xc0 LR [c03fc49c] chipsfb_pci_init+0x160/0x580 --- interrupt: 600 [ca021cd0] [c03fc46c] chipsfb_pci_init+0x130/0x580 (unreliable) [ca021d20] [c03a3a70] pci_device_probe+0xf8/0x1b8 [ca021d50] [c043d584] really_probe.part.0+0xac/0x388 [ca021d70] [c043d914] __driver_probe_device+0xb4/0x170 [ca021d90] [c043da18] driver_probe_device+0x48/0x144 [ca021dc0] [c043e318] __driver_attach+0x11c/0x1c4 [ca021de0] [c043ad30] bus_for_each_dev+0x88/0xf0 [ca021e10] [c043c724] bus_add_driver+0x190/0x22c [ca021e40] [c043ee94] driver_register+0x9c/0x170 [ca021e60] [c0006c28] do_one_initcall+0x54/0x1ec [ca021ed0] [c08246e4] kernel_init_freeable+0x1c0/0x270 [ca021f10] [c0006fdc] kernel_init+0x28/0x11c [ca021f30] [c0017148] ret_from_kernel_thread+0x14/0x1c Instruction dump: 7d4601a4 39490777 7d4701a4 39490888 7d4801a4 39490999 7d4901a4 39290aaa 7d2a01a4 4c00012c 4bfffe88 0fe00000 <4bfffe80> 9421fff0 38210010 48001970
This is due to 'dcbz' instruction being used on non-cached memory. 'dcbz' instruction is used by memset() to zeroize a complete cacheline at once, and memset() is not expected to be used on non cached memory.
When performing a 'sparse' check on fbdev driver, it also appears that the use of memset() is unexpected:
drivers/video/fbdev/chipsfb.c:334:17: warning: incorrect type in argument 1 (different address spaces) drivers/video/fbdev/chipsfb.c:334:17: expected void * drivers/video/fbdev/chipsfb.c:334:17: got char [noderef] __iomem *screen_base drivers/video/fbdev/chipsfb.c:334:15: warning: memset with byte count of 1048576
Use fb_memset() instead of memset(). fb_memset() is defined as memset_io() for powerpc.
Fixes: 8c8709334cec ("[PATCH] ppc32: Remove CONFIG_PMAC_PBOOK") Reported-by: Stan Johnson userm57@yahoo.com Cc: Finn Thain fthain@linux-m68k.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu --- drivers/video/fbdev/chipsfb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/chipsfb.c b/drivers/video/fbdev/chipsfb.c index 998067b701fa..393894af26f8 100644 --- a/drivers/video/fbdev/chipsfb.c +++ b/drivers/video/fbdev/chipsfb.c @@ -331,7 +331,7 @@ static const struct fb_var_screeninfo chipsfb_var = {
static void init_chips(struct fb_info *p, unsigned long addr) { - memset(p->screen_base, 0, 0x100000); + fb_memset(p->screen_base, 0, 0x100000);
p->fix = chipsfb_fix; p->fix.smem_start = addr;