This patch fix the problem with rootfs on JFFS2 with early printk
console turned on.
The origin version used TLB63 for temporary early printk mapping.
The code expect that kernel is not able to use all 64 TLB entries
till early printk console is remapped by ioremap. After that
temporary mapping on TLB63 is silently lost.
This expectation give the opportunity to have early console pretty
early.
Microblaze systems with JFFS2 rootfs with early printk console turned on
used more than 64 TLB entries before kernel can remap early console.
Based on that kernel does access to bad area because early printk mapping
is rewritten.
This patch introduces tlb_skip variable which dynamically stores number
of skipped TLB entries from the TLB0. skip_tlb=2 means that TLB0 and TLB1
should be skipped.
MICROBLAZE_TLB_SKIP defines how many TLB is skipped at the kernel start.
They can be used for user purpose.
TLB 63 is used for temporary LMB mapping (MICROBLAZE_LMB_TLB_ID).
Also clean TLBLO when kernel starts.
For specific kernel sizes kernel can use just one TLB. Detect this case
and use the second TLB for general purpose.
Change _tlbia function to flush TLB entries from tlb_skip to TLB_SIZE.
Export tlb_skip size through debugfs.
Signed-off-by: Michal Simek <monstr@monstr.eu>
TLB skip size direct how many TLBs is skipped.
Currently TLB0 and TLB1 are used for Linux kernel mapping
that's why their are skipped.
Signed-off-by: Michal Simek <monstr@monstr.eu>
Current implementation doesn't handle dcache_line_length
correctly that's why is better to use generic memcpy.
Cache optimized function could be good way howto improve
performance but must be based on benchmarking not blind
function like this.
Signed-off-by: Michal Simek <monstr@monstr.eu>
TLB size was hardcoded in asm code. This patch brings ability
to change TLB size only in one place. (mmu.h).
Signed-off-by: Michal Simek <monstr@monstr.eu>
Problem arise when is incopatibility between kernel/dts/pvr
and kernel tries to announce it. Early printk device
(uartlite in our case) was in TLB 2 and when kernel
extract DTB it necessary to allocate at least one
TLB at the end of memory. First free TLB was number two
where was early printk. But checking mechanism (kernel/dts/pvr)
was after extrahing but TLB 2 was different. This caused
that kernel hung up.
Moving early printk device to TLB 63 solve it and we don't
protect it which means that we can use early_printk messages
only for initial parts of kernel then we rewrite TLB 63.
Reported-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>
Michal Simek