arch/arc/lib/cache.c

/*
 * Copyright (C) 2013-2014 Synopsys, Inc. All rights reserved.
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <config.h>
#include <common.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <asm/arcregs.h>
#include <asm/arc-bcr.h>
#include <asm/cache.h>

/*
 * [ NOTE 1 ]:
 * Data cache (L1 D$ or SL$) entire invalidate operation or data cache disable
 * operation may result in unexpected behavior and data loss even if we flush
 * data cache right before invalidation. That may happens if we store any context
 * on stack (like we store BLINK register on stack before function call).
 * BLINK register is the register where return address is automatically saved
 * when we do function call with instructions like 'bl'.
 *
 * There is the real example:
 * We may hang in the next code as we store any BLINK register on stack in
 * invalidate_dcache_all() function.
 *
 * void flush_dcache_all() {
 *     __dc_entire_op(OP_FLUSH);
 *     // Other code //
 * }
 *
 * void invalidate_dcache_all() {
 *     __dc_entire_op(OP_INV);
 *     // Other code //
 * }
 *
 * void foo(void) {
 *     flush_dcache_all();
 *     invalidate_dcache_all();
 * }
 *
 * Now let's see what really happens during that code execution:
 *
 * foo()
 *   |->> call flush_dcache_all
 *     [return address is saved to BLINK register]
 *     [push BLINK] (save to stack)              ![point 1]
 *     |->> call __dc_entire_op(OP_FLUSH)
 *         [return address is saved to BLINK register]
 *         [flush L1 D$]
 *         return [jump to BLINK]
 *     <<------
 *     [other flush_dcache_all code]
 *     [pop BLINK] (get from stack)
 *     return [jump to BLINK]
 *   <<------
 *   |->> call invalidate_dcache_all
 *     [return address is saved to BLINK register]
 *     [push BLINK] (save to stack)               ![point 2]
 *     |->> call __dc_entire_op(OP_FLUSH)
 *         [return address is saved to BLINK register]
 *         [invalidate L1 D$]                 ![point 3]
 *         // Oops!!!
 *         // We lose return address from invalidate_dcache_all function:
 *         // we save it to stack and invalidate L1 D$ after that!
 *         return [jump to BLINK]
 *     <<------
 *     [other invalidate_dcache_all code]
 *     [pop BLINK] (get from stack)
 *     // we don't have this data in L1 dcache as we invalidated it in [point 3]
 *     // so we get it from next memory level (for example DDR memory)
 *     // but in the memory we have value which we save in [point 1], which
 *     // is return address from flush_dcache_all function (instead of
 *     // address from current invalidate_dcache_all function which we
 *     // saved in [point 2] !)
 *     return [jump to BLINK]
 *   <<------
 *   // As BLINK points to invalidate_dcache_all, we call it again and
 *   // loop forever.
 *
 * Fortunately we may fix that by using flush & invalidation of D$ with a single
 * one instruction (instead of flush and invalidation instructions pair) and
 * enabling force function inline with '__attribute__((always_inline))' gcc
 * attribute to avoid any function call (and BLINK store) between cache flush
 * and disable.
 */

/* Bit values in IC_CTRL */
#define IC_CTRL_CACHE_DISABLE	BIT(0)

/* Bit values in DC_CTRL */
#define DC_CTRL_CACHE_DISABLE	BIT(0)
#define DC_CTRL_INV_MODE_FLUSH	BIT(6)
#define DC_CTRL_FLUSH_STATUS	BIT(8)
#define CACHE_VER_NUM_MASK	0xF

#define OP_INV			BIT(0)
#define OP_FLUSH		BIT(1)
#define OP_FLUSH_N_INV		(OP_FLUSH | OP_INV)

/* Bit val in SLC_CONTROL */
#define SLC_CTRL_DIS		0x001
#define SLC_CTRL_IM		0x040
#define SLC_CTRL_BUSY		0x100
#define SLC_CTRL_RGN_OP_INV	0x200

/*
 * By default that variable will fall into .bss section.
 * But .bss section is not relocated and so it will be initilized before
 * relocation but will be used after being zeroed.
 */
int l1_line_sz __section(".data");
bool dcache_exists __section(".data") = false;
bool icache_exists __section(".data") = false;

#define CACHE_LINE_MASK		(~(l1_line_sz - 1))

int slc_line_sz __section(".data");
bool slc_exists __section(".data") = false;
bool ioc_exists __section(".data") = false;
bool pae_exists __section(".data") = false;

/* To force enable IOC set ioc_enable to 'true' */
bool ioc_enable __section(".data") = false;

void read_decode_mmu_bcr(void)
{
	/* TODO: should we compare mmu version from BCR and from CONFIG? */
#if (CONFIG_ARC_MMU_VER >= 4)
	union bcr_mmu_4 mmu4;

	mmu4.word = read_aux_reg(ARC_AUX_MMU_BCR);

	pae_exists = !!mmu4.fields.pae;
#endif /* (CONFIG_ARC_MMU_VER >= 4) */
}

static void __slc_entire_op(const int op)
{
	unsigned int ctrl;

	if (!slc_exists)
		return;

	ctrl = read_aux_reg(ARC_AUX_SLC_CTRL);

	if (!(op & OP_FLUSH))		/* i.e. OP_INV */
		ctrl &= ~SLC_CTRL_IM;	/* clear IM: Disable flush before Inv */
	else
		ctrl |= SLC_CTRL_IM;

	write_aux_reg(ARC_AUX_SLC_CTRL, ctrl);

	if (op & OP_INV)	/* Inv or flush-n-inv use same cmd reg */
		write_aux_reg(ARC_AUX_SLC_INVALIDATE, 0x1);
	else
		write_aux_reg(ARC_AUX_SLC_FLUSH, 0x1);

	/* Make sure "busy" bit reports correct stataus, see STAR 9001165532 */
	read_aux_reg(ARC_AUX_SLC_CTRL);

	/* Important to wait for flush to complete */
	while (read_aux_reg(ARC_AUX_SLC_CTRL) & SLC_CTRL_BUSY);
}

static void slc_upper_region_init(void)
{
	/*
	 * ARC_AUX_SLC_RGN_END1 and ARC_AUX_SLC_RGN_START1 are always == 0
	 * as we don't use PAE40.
	 */
	write_aux_reg(ARC_AUX_SLC_RGN_END1, 0);
	write_aux_reg(ARC_AUX_SLC_RGN_START1, 0);
}

static void __slc_rgn_op(unsigned long paddr, unsigned long sz, const int op)
{
#ifdef CONFIG_ISA_ARCV2

	unsigned int ctrl;
	unsigned long end;

	if (!slc_exists)
		return;

	/*
	 * The Region Flush operation is specified by CTRL.RGN_OP[11..9]
	 *  - b'000 (default) is Flush,
	 *  - b'001 is Invalidate if CTRL.IM == 0
	 *  - b'001 is Flush-n-Invalidate if CTRL.IM == 1
	 */
	ctrl = read_aux_reg(ARC_AUX_SLC_CTRL);

	/* Don't rely on default value of IM bit */
	if (!(op & OP_FLUSH))		/* i.e. OP_INV */
		ctrl &= ~SLC_CTRL_IM;	/* clear IM: Disable flush before Inv */
	else
		ctrl |= SLC_CTRL_IM;

	if (op & OP_INV)
		ctrl |= SLC_CTRL_RGN_OP_INV;	/* Inv or flush-n-inv */
	else
		ctrl &= ~SLC_CTRL_RGN_OP_INV;

	write_aux_reg(ARC_AUX_SLC_CTRL, ctrl);

	/*
	 * Lower bits are ignored, no need to clip
	 * END needs to be setup before START (latter triggers the operation)
	 * END can't be same as START, so add (l2_line_sz - 1) to sz
	 */
	end = paddr + sz + slc_line_sz - 1;

	/*
	 * Upper addresses (ARC_AUX_SLC_RGN_END1 and ARC_AUX_SLC_RGN_START1)
	 * are always == 0 as we don't use PAE40, so we only setup lower ones
	 * (ARC_AUX_SLC_RGN_END and ARC_AUX_SLC_RGN_START)
	 */
	write_aux_reg(ARC_AUX_SLC_RGN_END, end);
	write_aux_reg(ARC_AUX_SLC_RGN_START, paddr);

	/* Make sure "busy" bit reports correct stataus, see STAR 9001165532 */
	read_aux_reg(ARC_AUX_SLC_CTRL);

	while (read_aux_reg(ARC_AUX_SLC_CTRL) & SLC_CTRL_BUSY);

#endif /* CONFIG_ISA_ARCV2 */
}

static void arc_ioc_setup(void)
{
	/* IOC Aperture start is equal to DDR start */
	unsigned int ap_base = CONFIG_SYS_SDRAM_BASE;
	/* IOC Aperture size is equal to DDR size */
	long ap_size = CONFIG_SYS_SDRAM_SIZE;

	flush_n_invalidate_dcache_all();

	if (!is_power_of_2(ap_size) || ap_size < 4096)
		panic("IOC Aperture size must be power of 2 and bigger 4Kib");

	/*
	 * IOC Aperture size decoded as 2 ^ (SIZE + 2) KB,
	 * so setting 0x11 implies 512M, 0x12 implies 1G...
	 */
	write_aux_reg(ARC_AUX_IO_COH_AP0_SIZE,
		      order_base_2(ap_size / 1024) - 2);

	/* IOC Aperture start must be aligned to the size of the aperture */
	if (ap_base % ap_size != 0)
		panic("IOC Aperture start must be aligned to the size of the aperture");

	write_aux_reg(ARC_AUX_IO_COH_AP0_BASE, ap_base >> 12);
	write_aux_reg(ARC_AUX_IO_COH_PARTIAL, 1);
	write_aux_reg(ARC_AUX_IO_COH_ENABLE, 1);
}

static void read_decode_cache_bcr_arcv2(void)
{
#ifdef CONFIG_ISA_ARCV2

	union bcr_slc_cfg slc_cfg;
	union bcr_clust_cfg cbcr;
	union bcr_generic sbcr;

	sbcr.word = read_aux_reg(ARC_BCR_SLC);
	if (sbcr.fields.ver) {
		slc_cfg.word = read_aux_reg(ARC_AUX_SLC_CONFIG);
		slc_exists = true;
		slc_line_sz = (slc_cfg.fields.lsz == 0) ? 128 : 64;
	}

	cbcr.word = read_aux_reg(ARC_BCR_CLUSTER);
	if (cbcr.fields.c && ioc_enable)
		ioc_exists = true;

#endif /* CONFIG_ISA_ARCV2 */
}

void read_decode_cache_bcr(void)
{
	int dc_line_sz = 0, ic_line_sz = 0;
	union bcr_di_cache ibcr, dbcr;

	ibcr.word = read_aux_reg(ARC_BCR_IC_BUILD);
	if (ibcr.fields.ver) {
		icache_exists = true;
		l1_line_sz = ic_line_sz = 8 << ibcr.fields.line_len;
		if (!ic_line_sz)
			panic("Instruction exists but line length is 0\n");
	}

	dbcr.word = read_aux_reg(ARC_BCR_DC_BUILD);
	if (dbcr.fields.ver) {
		dcache_exists = true;
		l1_line_sz = dc_line_sz = 16 << dbcr.fields.line_len;
		if (!dc_line_sz)
			panic("Data cache exists but line length is 0\n");
	}

	if (ic_line_sz && dc_line_sz && (ic_line_sz != dc_line_sz))
		panic("Instruction and data cache line lengths differ\n");
}

void cache_init(void)
{
	read_decode_cache_bcr();

	if (is_isa_arcv2())
		read_decode_cache_bcr_arcv2();

	if (is_isa_arcv2() && ioc_exists)
		arc_ioc_setup();

	read_decode_mmu_bcr();

	/*
	 * ARC_AUX_SLC_RGN_START1 and ARC_AUX_SLC_RGN_END1 register exist
	 * only if PAE exists in current HW. So we had to check pae_exist
	 * before using them.
	 */
	if (is_isa_arcv2() && slc_exists && pae_exists)
		slc_upper_region_init();
}

int icache_status(void)
{
	if (!icache_exists)
		return 0;

	if (read_aux_reg(ARC_AUX_IC_CTRL) & IC_CTRL_CACHE_DISABLE)
		return 0;
	else
		return 1;
}

void icache_enable(void)
{
	if (icache_exists)
		write_aux_reg(ARC_AUX_IC_CTRL, read_aux_reg(ARC_AUX_IC_CTRL) &
			      ~IC_CTRL_CACHE_DISABLE);
}

void icache_disable(void)
{
	if (icache_exists)
		write_aux_reg(ARC_AUX_IC_CTRL, read_aux_reg(ARC_AUX_IC_CTRL) |
			      IC_CTRL_CACHE_DISABLE);
}

/* IC supports only invalidation */
static inline void __ic_entire_invalidate(void)
{
	if (!icache_status())
		return;

	/* Any write to IC_IVIC register triggers invalidation of entire I$ */
	write_aux_reg(ARC_AUX_IC_IVIC, 1);
	/*
	 * As per ARC HS databook (see chapter 5.3.3.2)
	 * it is required to add 3 NOPs after each write to IC_IVIC.
	 */
	__builtin_arc_nop();
	__builtin_arc_nop();
	__builtin_arc_nop();
	read_aux_reg(ARC_AUX_IC_CTRL);  /* blocks */
}

void invalidate_icache_all(void)
{
	__ic_entire_invalidate();

	if (is_isa_arcv2())
		__slc_entire_op(OP_INV);
}

int dcache_status(void)
{
	if (!dcache_exists)
		return 0;

	if (read_aux_reg(ARC_AUX_DC_CTRL) & DC_CTRL_CACHE_DISABLE)
		return 0;
	else
		return 1;
}

void dcache_enable(void)
{
	if (!dcache_exists)
		return;

	write_aux_reg(ARC_AUX_DC_CTRL, read_aux_reg(ARC_AUX_DC_CTRL) &
		      ~(DC_CTRL_INV_MODE_FLUSH | DC_CTRL_CACHE_DISABLE));
}

void dcache_disable(void)
{
	if (!dcache_exists)
		return;

	write_aux_reg(ARC_AUX_DC_CTRL, read_aux_reg(ARC_AUX_DC_CTRL) |
		      DC_CTRL_CACHE_DISABLE);
}

/* Common Helper for Line Operations on D-cache */
static inline void __dcache_line_loop(unsigned long paddr, unsigned long sz,
				      const int cacheop)
{
	unsigned int aux_cmd;
	int num_lines;

	/* d$ cmd: INV (discard or wback-n-discard) OR FLUSH (wback) */
	aux_cmd = cacheop & OP_INV ? ARC_AUX_DC_IVDL : ARC_AUX_DC_FLDL;

	sz += paddr & ~CACHE_LINE_MASK;
	paddr &= CACHE_LINE_MASK;

	num_lines = DIV_ROUND_UP(sz, l1_line_sz);

	while (num_lines-- > 0) {
#if (CONFIG_ARC_MMU_VER == 3)
		write_aux_reg(ARC_AUX_DC_PTAG, paddr);
#endif
		write_aux_reg(aux_cmd, paddr);
		paddr += l1_line_sz;
	}
}

static void __before_dc_op(const int op)
{
	unsigned int ctrl;

	ctrl = read_aux_reg(ARC_AUX_DC_CTRL);

	/* IM bit implies flush-n-inv, instead of vanilla inv */
	if (op == OP_INV)
		ctrl &= ~DC_CTRL_INV_MODE_FLUSH;
	else
		ctrl |= DC_CTRL_INV_MODE_FLUSH;

	write_aux_reg(ARC_AUX_DC_CTRL, ctrl);
}

static void __after_dc_op(const int op)
{
	if (op & OP_FLUSH)	/* flush / flush-n-inv both wait */
		while (read_aux_reg(ARC_AUX_DC_CTRL) & DC_CTRL_FLUSH_STATUS);
}

static inline void __dc_entire_op(const int cacheop)
{
	int aux;

	if (!dcache_status())
		return;

	__before_dc_op(cacheop);

	if (cacheop & OP_INV)	/* Inv or flush-n-inv use same cmd reg */
		aux = ARC_AUX_DC_IVDC;
	else
		aux = ARC_AUX_DC_FLSH;

	write_aux_reg(aux, 0x1);

	__after_dc_op(cacheop);
}

static inline void __dc_line_op(unsigned long paddr, unsigned long sz,
				const int cacheop)
{
	if (!dcache_status())
		return;

	__before_dc_op(cacheop);
	__dcache_line_loop(paddr, sz, cacheop);
	__after_dc_op(cacheop);
}

void invalidate_dcache_range(unsigned long start, unsigned long end)
{
	if (start >= end)
		return;

	/*
	 * ARCv1                  -> call __dc_line_op
	 * ARCv2 && no IOC        -> call __dc_line_op; call __slc_rgn_op
	 * ARCv2 && IOC enabled   -> nothing
	 */
	if (!is_isa_arcv2() || !ioc_exists)
		__dc_line_op(start, end - start, OP_INV);

	if (is_isa_arcv2() && !ioc_exists)
		__slc_rgn_op(start, end - start, OP_INV);
}

void flush_dcache_range(unsigned long start, unsigned long end)
{
	if (start >= end)
		return;

	/*
	 * ARCv1                  -> call __dc_line_op
	 * ARCv2 && no IOC        -> call __dc_line_op; call __slc_rgn_op
	 * ARCv2 && IOC enabled   -> nothing
	 */
	if (!is_isa_arcv2() || !ioc_exists)
		__dc_line_op(start, end - start, OP_FLUSH);

	if (is_isa_arcv2() && !ioc_exists)
		__slc_rgn_op(start, end - start, OP_FLUSH);
}

void flush_cache(unsigned long start, unsigned long size)
{
	flush_dcache_range(start, start + size);
}

/*
 * As invalidate_dcache_all() is not used in generic U-Boot code and as we
 * don't need it in arch/arc code alone (invalidate without flush) we implement
 * flush_n_invalidate_dcache_all (flush and invalidate in 1 operation) because
 * it's much safer. See [ NOTE 1 ] for more details.
 */
void flush_n_invalidate_dcache_all(void)
{
	__dc_entire_op(OP_FLUSH_N_INV);

	if (is_isa_arcv2())
		__slc_entire_op(OP_FLUSH_N_INV);
}

void flush_dcache_all(void)
{
	__dc_entire_op(OP_FLUSH);

	if (is_isa_arcv2())
		__slc_entire_op(OP_FLUSH);
}