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Commit 95b0f9ea authored by Michal Simek's avatar Michal Simek
Browse files

microblaze: Improve TLB calculation for small systems 



Systems with small amount of memory need to be handled
differently. Linux can't allocate the whole 32MB with two TLBs
because then there is no MMU protection.

Signed-off-by: default avatarMichal Simek <monstr@monstr.eu>
parent 3a1d2676

arch/microblaze/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -259,6 +259,10 @@ config MICROBLAZE_32K_PAGES 


endchoice



config KERNEL_PAD

	hex "Kernel PAD for unpacking" if ADVANCED_OPTIONS

	default "0x80000" if MMU



endmenu



source "mm/Kconfig"

arch/microblaze/include/asm/setup.h

+2 −1
Original line number Diff line number Diff line
@@ -39,7 +39,8 @@ extern void of_platform_reset_gpio_probe(void); 
void time_init(void);

void init_IRQ(void);

void machine_early_init(const char *cmdline, unsigned int ram,

			unsigned int fdt, unsigned int msr);

		unsigned int fdt, unsigned int msr, unsigned int tlb0,

		unsigned int tlb1);



void machine_restart(char *cmd);

void machine_shutdown(void);

arch/microblaze/include/asm/system.h

+1 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ void default_idle(void); 
void free_init_pages(char *what, unsigned long begin, unsigned long end);

void free_initmem(void);

extern char *klimit;

extern unsigned long kernel_tlb;

extern void ret_from_fork(void);



extern void *alloc_maybe_bootmem(size_t size, gfp_t mask);

arch/microblaze/kernel/head.S

+93 −5
Original line number Diff line number Diff line
@@ -168,6 +168,53 @@ _invalidate: 
	addik	r3,r0, CONFIG_KERNEL_START /* Load the kernel virtual address */

	tophys(r4,r3)			/* Load the kernel physical address */



	/* start to do TLB calculation */

	addik	r12, r0, _end

	rsub	r12, r3, r12

	addik	r12, r12, CONFIG_KERNEL_PAD /* that's the pad */



	or r9, r0, r0 /* TLB0 = 0 */

	or r10, r0, r0 /* TLB1 = 0 */



	addik	r11, r12, -0x1000000

	bgei	r11, GT16 /* size is greater than 16MB */

	addik	r11, r12, -0x0800000

	bgei	r11, GT8 /* size is greater than 8MB */

	addik	r11, r12, -0x0400000

	bgei	r11, GT4 /* size is greater than 4MB */

	/* size is less than 4MB */

	addik	r11, r12, -0x0200000

	bgei	r11, GT2 /* size is greater than 2MB */

	addik	r9, r0, 0x0100000 /* TLB0 must be 1MB */

	addik	r11, r12, -0x0100000

	bgei	r11, GT1 /* size is greater than 1MB */

	/* TLB1 is 0 which is setup above */

	bri tlb_end

GT4: /* r11 contains the rest - will be either 1 or 4 */

	ori r9, r0, 0x400000 /* TLB0 is 4MB */

	bri TLB1

GT16: /* TLB0 is 16MB */

	addik	r9, r0, 0x1000000 /* means TLB0 is 16MB */

TLB1:

	/* must be used r2 because of substract if failed */

	addik	r2, r11, -0x0400000

	bgei	r2, GT20 /* size is greater than 16MB */

	/* size is >16MB and <20MB */

	addik	r11, r11, -0x0100000

	bgei	r11, GT17 /* size is greater than 17MB */

	/* kernel is >16MB and < 17MB */

GT1:

	addik	r10, r0, 0x0100000 /* means TLB1 is 1MB */

	bri tlb_end

GT2: /* TLB0 is 0 and TLB1 will be 4MB */

GT17: /* TLB1 is 4MB - kernel size <20MB */

	addik	r10, r0, 0x0400000 /* means TLB1 is 4MB */

	bri tlb_end

GT8: /* TLB0 is still zero that's why I can use only TLB1 */

GT20: /* TLB1 is 16MB - kernel size >20MB */

	addik	r10, r0, 0x1000000 /* means TLB1 is 16MB */

tlb_end:



	/*

	 * Configure and load two entries into TLB slots 0 and 1.

	 * In case we are pinning TLBs, these are reserved in by the
@@ -177,16 +224,56 @@ _invalidate: 
	andi	r4,r4,0xfffffc00	/* Mask off the real page number */

	ori	r4,r4,(TLB_WR | TLB_EX)	/* Set the write and execute bits */



	/* TLB0 can be zeroes that's why we not setup it */

	beqi	r9, jump_over



	/* look at the code below */

	ori	r30, r0, 0x200

	andi	r29, r9, 0x100000

	bneid	r29, 1f

	addik	r30, r30, 0x80

	andi	r29, r9, 0x400000

	bneid	r29, 1f

	addik	r30, r30, 0x80

	andi	r29, r9, 0x1000000

	bneid	r29, 1f

	addik	r30, r30, 0x80

1:

	ori r11, r30, 0



	andi	r3,r3,0xfffffc00	/* Mask off the effective page number */

	ori	r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))

	ori	r3,r3,(TLB_VALID)

	or	r3, r3, r11



	mts     rtlbx,r0		/* TLB slow 0 */



	mts	rtlblo,r4		/* Load the data portion of the entry */

	mts	rtlbhi,r3		/* Load the tag portion of the entry */



	addik	r4, r4, 0x01000000	/* Map next 16 M entries */

	addik	r3, r3, 0x01000000

jump_over:

	/* TLB1 can be zeroes that's why we not setup it */

	beqi	r10, jump_over2



	/* look at the code below */

	ori	r30, r0, 0x200

	andi	r29, r10, 0x100000

	bneid	r29, 1f

	addik	r30, r30, 0x80

	andi	r29, r10, 0x400000

	bneid	r29, 1f

	addik	r30, r30, 0x80

	andi	r29, r10, 0x1000000

	bneid	r29, 1f

	addik	r30, r30, 0x80

1:

	ori r12, r30, 0



	addk	r4, r4, r9	/* previous addr + TLB0 size */

	addk	r3, r3, r9



	andi	r3,r3,0xfffffc00	/* Mask off the effective page number */

	ori	r3,r3,(TLB_VALID)

	or	r3, r3, r12



	ori	r6,r0,1			/* TLB slot 1 */

	mts     rtlbx,r6
@@ -194,6 +281,7 @@ _invalidate: 
	mts	rtlblo,r4		/* Load the data portion of the entry */

	mts	rtlbhi,r3		/* Load the tag portion of the entry */



jump_over2:

	/*

	 * Load a TLB entry for LMB, since we need access to

	 * the exception vectors, using a 4k real==virtual mapping.
@@ -237,8 +325,8 @@ start_here: 
	 * Please see $(ARCH)/mach-$(SUBARCH)/setup.c for

	 * the function.

	 */

	addik	r9, r0, machine_early_init

	brald	r15, r9

	addik	r11, r0, machine_early_init

	brald	r15, r11

	nop



#ifndef CONFIG_MMU

arch/microblaze/kernel/setup.c

+10 −1
Original line number Diff line number Diff line
@@ -97,8 +97,11 @@ inline unsigned get_romfs_len(unsigned *addr) 
}

#endif	/* CONFIG_MTD_UCLINUX_EBSS */



unsigned long kernel_tlb;



void __init machine_early_init(const char *cmdline, unsigned int ram,

		unsigned int fdt, unsigned int msr)

		unsigned int fdt, unsigned int msr, unsigned int tlb0,

		unsigned int tlb1)

{

	unsigned long *src, *dst;

	unsigned int offset = 0;
@@ -145,6 +148,12 @@ void __init machine_early_init(const char *cmdline, unsigned int ram, 
	setup_early_printk(NULL);

#endif



	/* setup kernel_tlb after BSS cleaning

	 * Maybe worth to move to asm code */

	kernel_tlb = tlb0 + tlb1;

	/* printk("TLB1 0x%08x, TLB0 0x%08x, tlb 0x%x\n", tlb0,

							tlb1, kernel_tlb); */



	printk("Ramdisk addr 0x%08x, ", ram);

	if (fdt)

		printk("FDT at 0x%08x\n", fdt);