def_bool y
config ARCH_DISCONTIGMEM_ENABLE
- def_bool y
+ def_bool n
config ARCH_FLATMEM_ENABLE
def_bool y
config ARC_HAS_COH_CACHES
def_bool n
-config ARC_HAS_REENTRANT_IRQ_LV2
- def_bool n
-
config ARC_MCIP
bool "ARConnect Multicore IP (MCIP) Support "
depends on ISA_ARCV2
if ISA_ARCOMPACT
config ARC_COMPACT_IRQ_LEVELS
- bool "ARCompact IRQ Priorities: High(2)/Low(1)"
+ bool "Setup Timer IRQ as high Priority"
default n
- # Timer HAS to be high priority, for any other high priority config
- select ARC_IRQ3_LV2
# if SMP, LV2 enabled ONLY if ARC implementation has LV2 re-entrancy
- depends on !SMP || ARC_HAS_REENTRANT_IRQ_LV2
-
-if ARC_COMPACT_IRQ_LEVELS
-
-config ARC_IRQ3_LV2
- bool
-
-config ARC_IRQ5_LV2
- bool
-
-config ARC_IRQ6_LV2
- bool
-
-endif #ARC_COMPACT_IRQ_LEVELS
+ depends on !SMP
config ARC_FPU_SAVE_RESTORE
bool "Enable FPU state persistence across context switch"
default y
depends on !ARC_CANT_LLSC
-config ARC_STAR_9000923308
- bool "Workaround for llock/scond livelock"
- default n
- depends on ISA_ARCV2 && SMP && ARC_HAS_LLSC
-
config ARC_HAS_SWAPE
bool "Insn: SWAPE (endian-swap)"
default y
config HIGHMEM
bool "High Memory Support"
- select DISCONTIGMEM
+ select ARCH_DISCONTIGMEM_ENABLE
help
With ARC 2G:2G address split, only upper 2G is directly addressable by
kernel. Enable this to potentially allow access to rest of 2G and PAE
boot := arch/arc/boot
-#default target for make without any arguements.
+#default target for make without any arguments.
KBUILD_IMAGE := bootpImage
all: $(KBUILD_IMAGE)
/ {
- clock-frequency = <500000000>; /* 500 MHZ */
-
soc100 {
bus-frequency = <166666666>;
/ {
- clock-frequency = <500000000>; /* 500 MHZ */
-
soc100 {
bus-frequency = <166666666>;
/ {
compatible = "snps,arc";
- clock-frequency = <750000000>; /* 750 MHZ */
#address-cells = <1>;
#size-cells = <1>;
/ {
compatible = "snps,arc";
- clock-frequency = <90000000>;
#address-cells = <1>;
#size-cells = <1>;
/ {
compatible = "snps,arc";
- clock-frequency = <90000000>;
#address-cells = <1>;
#size-cells = <1>;
/ {
compatible = "ezchip,arc-nps";
- clock-frequency = <83333333>; /* 83.333333 MHZ */
#address-cells = <1>;
#size-cells = <1>;
interrupt-parent = <&intc>;
/ {
compatible = "snps,nsim";
- clock-frequency = <80000000>; /* 80 MHZ */
#address-cells = <1>;
#size-cells = <1>;
interrupt-parent = <&core_intc>;
/ {
compatible = "snps,nsimosci";
- clock-frequency = <20000000>; /* 20 MHZ */
#address-cells = <1>;
#size-cells = <1>;
interrupt-parent = <&core_intc>;
/ {
compatible = "snps,nsimosci_hs";
- clock-frequency = <20000000>; /* 20 MHZ */
#address-cells = <1>;
#size-cells = <1>;
interrupt-parent = <&core_intc>;
/ {
compatible = "snps,nsimosci_hs";
- clock-frequency = <5000000>; /* 5 MHZ */
#address-cells = <1>;
#size-cells = <1>;
interrupt-parent = <&core_intc>;
/ {
compatible = "snps,arc";
- clock-frequency = <80000000>; /* 80 MHZ */
#address-cells = <1>;
#size-cells = <1>;
chosen { };
/ {
compatible = "snps,arc";
- clock-frequency = <80000000>; /* 80 MHZ */
#address-cells = <1>;
#size-cells = <1>;
chosen { };
/ {
compatible = "snps,arc";
- clock-frequency = <80000000>; /* 80 MHZ */
#address-cells = <1>;
#size-cells = <1>;
chosen { };
/ {
compatible = "snps,arc";
- clock-frequency = <50000000>;
#address-cells = <1>;
#size-cells = <1>;
/ {
compatible = "snps,arc";
- clock-frequency = <50000000>;
#address-cells = <1>;
#size-cells = <1>;
#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
-#ifdef CONFIG_ARC_STAR_9000923308
-
-#define SCOND_FAIL_RETRY_VAR_DEF \
- unsigned int delay = 1, tmp; \
-
-#define SCOND_FAIL_RETRY_ASM \
- " bz 4f \n" \
- " ; --- scond fail delay --- \n" \
- " mov %[tmp], %[delay] \n" /* tmp = delay */ \
- "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \
- " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \
- " rol %[delay], %[delay] \n" /* delay *= 2 */ \
- " b 1b \n" /* start over */ \
- "4: ; --- success --- \n" \
-
-#define SCOND_FAIL_RETRY_VARS \
- ,[delay] "+&r" (delay),[tmp] "=&r" (tmp) \
-
-#else /* !CONFIG_ARC_STAR_9000923308 */
-
-#define SCOND_FAIL_RETRY_VAR_DEF
-
-#define SCOND_FAIL_RETRY_ASM \
- " bnz 1b \n" \
-
-#define SCOND_FAIL_RETRY_VARS
-
-#endif
-
#define ATOMIC_OP(op, c_op, asm_op) \
static inline void atomic_##op(int i, atomic_t *v) \
{ \
- unsigned int val; \
- SCOND_FAIL_RETRY_VAR_DEF \
+ unsigned int val; \
\
__asm__ __volatile__( \
"1: llock %[val], [%[ctr]] \n" \
" " #asm_op " %[val], %[val], %[i] \n" \
" scond %[val], [%[ctr]] \n" \
- " \n" \
- SCOND_FAIL_RETRY_ASM \
- \
+ " bnz 1b \n" \
: [val] "=&r" (val) /* Early clobber to prevent reg reuse */ \
- SCOND_FAIL_RETRY_VARS \
: [ctr] "r" (&v->counter), /* Not "m": llock only supports reg direct addr mode */ \
[i] "ir" (i) \
: "cc"); \
#define ATOMIC_OP_RETURN(op, c_op, asm_op) \
static inline int atomic_##op##_return(int i, atomic_t *v) \
{ \
- unsigned int val; \
- SCOND_FAIL_RETRY_VAR_DEF \
+ unsigned int val; \
\
/* \
* Explicit full memory barrier needed before/after as \
"1: llock %[val], [%[ctr]] \n" \
" " #asm_op " %[val], %[val], %[i] \n" \
" scond %[val], [%[ctr]] \n" \
- " \n" \
- SCOND_FAIL_RETRY_ASM \
- \
+ " bnz 1b \n" \
: [val] "=&r" (val) \
- SCOND_FAIL_RETRY_VARS \
: [ctr] "r" (&v->counter), \
[i] "ir" (i) \
: "cc"); \
* We need to be a bit more cautious here. What if a kernel bug in
* L1 ISR, caused SP to go whaco (some small value which looks like
* USER stk) and then we take L2 ISR.
- * Above brlo alone would treat it as a valid L1-L2 sceanrio
- * instead of shouting alound
+ * Above brlo alone would treat it as a valid L1-L2 scenario
+ * instead of shouting around
* The only feasible way is to make sure this L2 happened in
* L1 prelogue ONLY i.e. ilink2 is less than a pre-set marker in
* L1 ISR before it switches stack
local_flush_tlb_all();
/*
- * Above checke for rollover of 8 bit ASID in 32 bit container.
+ * Above check for rollover of 8 bit ASID in 32 bit container.
* If the container itself wrapped around, set it to a non zero
* "generation" to distinguish from no context
*/
* Page Tables are purely for Linux VM's consumption and the bits below are
* suited to that (uniqueness). Hence some are not implemented in the TLB and
* some have different value in TLB.
- * e.g. MMU v2: K_READ bit is 8 and so is GLOBAL (possible becoz they live in
+ * e.g. MMU v2: K_READ bit is 8 and so is GLOBAL (possible because they live in
* seperate PD0 and PD1, which combined forms a translation entry)
* while for PTE perspective, they are 8 and 9 respectively
* with MMU v3: Most bits (except SHARED) represent the exact hardware pos
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->sp)
/*
- * Where abouts of Task's sp, fp, blink when it was last seen in kernel mode.
+ * Where about of Task's sp, fp, blink when it was last seen in kernel mode.
* Look in process.c for details of kernel stack layout
*/
#define TSK_K_ESP(tsk) (tsk->thread.ksp)
* (1) These insn were introduced only in 4.10 release. So for older released
* support needed.
*
- * (2) In a SMP setup, the LLOCK/SCOND atomiticity across CPUs needs to be
+ * (2) In a SMP setup, the LLOCK/SCOND atomicity across CPUs needs to be
* gaurantted by the platform (not something which core handles).
* Assuming a platform won't, SMP Linux needs to use spinlocks + local IRQ
* disabling for atomicity.
#ifdef CONFIG_ARC_HAS_LLSC
-/*
- * A normal LLOCK/SCOND based system, w/o need for livelock workaround
- */
-#ifndef CONFIG_ARC_STAR_9000923308
-
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
unsigned int val;
smp_mb();
}
-#else /* CONFIG_ARC_STAR_9000923308 */
-
-/*
- * HS38x4 could get into a LLOCK/SCOND livelock in case of multiple overlapping
- * coherency transactions in the SCU. The exclusive line state keeps rotating
- * among contenting cores leading to a never ending cycle. So break the cycle
- * by deferring the retry of failed exclusive access (SCOND). The actual delay
- * needed is function of number of contending cores as well as the unrelated
- * coherency traffic from other cores. To keep the code simple, start off with
- * small delay of 1 which would suffice most cases and in case of contention
- * double the delay. Eventually the delay is sufficient such that the coherency
- * pipeline is drained, thus a subsequent exclusive access would succeed.
- */
-
-#define SCOND_FAIL_RETRY_VAR_DEF \
- unsigned int delay, tmp; \
-
-#define SCOND_FAIL_RETRY_ASM \
- " ; --- scond fail delay --- \n" \
- " mov %[tmp], %[delay] \n" /* tmp = delay */ \
- "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \
- " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \
- " rol %[delay], %[delay] \n" /* delay *= 2 */ \
- " b 1b \n" /* start over */ \
- " \n" \
- "4: ; --- done --- \n" \
-
-#define SCOND_FAIL_RETRY_VARS \
- ,[delay] "=&r" (delay), [tmp] "=&r" (tmp) \
-
-static inline void arch_spin_lock(arch_spinlock_t *lock)
-{
- unsigned int val;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[slock]] \n"
- " breq %[val], %[LOCKED], 0b \n" /* spin while LOCKED */
- " scond %[LOCKED], [%[slock]] \n" /* acquire */
- " bz 4f \n" /* done */
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val)
- SCOND_FAIL_RETRY_VARS
- : [slock] "r" (&(lock->slock)),
- [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
- : "memory", "cc");
-
- smp_mb();
-}
-
-/* 1 - lock taken successfully */
-static inline int arch_spin_trylock(arch_spinlock_t *lock)
-{
- unsigned int val, got_it = 0;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[slock]] \n"
- " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
- " scond %[LOCKED], [%[slock]] \n" /* acquire */
- " bz.d 4f \n"
- " mov.z %[got_it], 1 \n" /* got it */
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val),
- [got_it] "+&r" (got_it)
- SCOND_FAIL_RETRY_VARS
- : [slock] "r" (&(lock->slock)),
- [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
- : "memory", "cc");
-
- smp_mb();
-
- return got_it;
-}
-
-static inline void arch_spin_unlock(arch_spinlock_t *lock)
-{
- smp_mb();
-
- lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
-
- smp_mb();
-}
-
-/*
- * Read-write spinlocks, allowing multiple readers but only one writer.
- * Unfair locking as Writers could be starved indefinitely by Reader(s)
- */
-
-static inline void arch_read_lock(arch_rwlock_t *rw)
-{
- unsigned int val;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- /*
- * zero means writer holds the lock exclusively, deny Reader.
- * Otherwise grant lock to first/subseq reader
- *
- * if (rw->counter > 0) {
- * rw->counter--;
- * ret = 1;
- * }
- */
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[rwlock]] \n"
- " brls %[val], %[WR_LOCKED], 0b\n" /* <= 0: spin while write locked */
- " sub %[val], %[val], 1 \n" /* reader lock */
- " scond %[val], [%[rwlock]] \n"
- " bz 4f \n" /* done */
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val)
- SCOND_FAIL_RETRY_VARS
- : [rwlock] "r" (&(rw->counter)),
- [WR_LOCKED] "ir" (0)
- : "memory", "cc");
-
- smp_mb();
-}
-
-/* 1 - lock taken successfully */
-static inline int arch_read_trylock(arch_rwlock_t *rw)
-{
- unsigned int val, got_it = 0;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[rwlock]] \n"
- " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
- " sub %[val], %[val], 1 \n" /* counter-- */
- " scond %[val], [%[rwlock]] \n"
- " bz.d 4f \n"
- " mov.z %[got_it], 1 \n" /* got it */
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val),
- [got_it] "+&r" (got_it)
- SCOND_FAIL_RETRY_VARS
- : [rwlock] "r" (&(rw->counter)),
- [WR_LOCKED] "ir" (0)
- : "memory", "cc");
-
- smp_mb();
-
- return got_it;
-}
-
-static inline void arch_write_lock(arch_rwlock_t *rw)
-{
- unsigned int val;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- /*
- * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
- * deny writer. Otherwise if unlocked grant to writer
- * Hence the claim that Linux rwlocks are unfair to writers.
- * (can be starved for an indefinite time by readers).
- *
- * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
- * rw->counter = 0;
- * ret = 1;
- * }
- */
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[rwlock]] \n"
- " brne %[val], %[UNLOCKED], 0b \n" /* while !UNLOCKED spin */
- " mov %[val], %[WR_LOCKED] \n"
- " scond %[val], [%[rwlock]] \n"
- " bz 4f \n"
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val)
- SCOND_FAIL_RETRY_VARS
- : [rwlock] "r" (&(rw->counter)),
- [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
- [WR_LOCKED] "ir" (0)
- : "memory", "cc");
-
- smp_mb();
-}
-
-/* 1 - lock taken successfully */
-static inline int arch_write_trylock(arch_rwlock_t *rw)
-{
- unsigned int val, got_it = 0;
- SCOND_FAIL_RETRY_VAR_DEF;
-
- smp_mb();
-
- __asm__ __volatile__(
- "0: mov %[delay], 1 \n"
- "1: llock %[val], [%[rwlock]] \n"
- " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
- " mov %[val], %[WR_LOCKED] \n"
- " scond %[val], [%[rwlock]] \n"
- " bz.d 4f \n"
- " mov.z %[got_it], 1 \n" /* got it */
- " \n"
- SCOND_FAIL_RETRY_ASM
-
- : [val] "=&r" (val),
- [got_it] "+&r" (got_it)
- SCOND_FAIL_RETRY_VARS
- : [rwlock] "r" (&(rw->counter)),
- [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
- [WR_LOCKED] "ir" (0)
- : "memory", "cc");
-
- smp_mb();
-
- return got_it;
-}
-
-static inline void arch_read_unlock(arch_rwlock_t *rw)
-{
- unsigned int val;
-
- smp_mb();
-
- /*
- * rw->counter++;
- */
- __asm__ __volatile__(
- "1: llock %[val], [%[rwlock]] \n"
- " add %[val], %[val], 1 \n"
- " scond %[val], [%[rwlock]] \n"
- " bnz 1b \n"
- " \n"
- : [val] "=&r" (val)
- : [rwlock] "r" (&(rw->counter))
- : "memory", "cc");
-
- smp_mb();
-}
-
-static inline void arch_write_unlock(arch_rwlock_t *rw)
-{
- unsigned int val;
-
- smp_mb();
-
- /*
- * rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
- */
- __asm__ __volatile__(
- "1: llock %[val], [%[rwlock]] \n"
- " scond %[UNLOCKED], [%[rwlock]]\n"
- " bnz 1b \n"
- " \n"
- : [val] "=&r" (val)
- : [rwlock] "r" (&(rw->counter)),
- [UNLOCKED] "r" (__ARCH_RW_LOCK_UNLOCKED__)
- : "memory", "cc");
-
- smp_mb();
-}
-
-#undef SCOND_FAIL_RETRY_VAR_DEF
-#undef SCOND_FAIL_RETRY_ASM
-#undef SCOND_FAIL_RETRY_VARS
-
-#endif /* CONFIG_ARC_STAR_9000923308 */
-
#else /* !CONFIG_ARC_HAS_LLSC */
static inline void arch_spin_lock(arch_spinlock_t *lock)
/*
* _TIF_ALLWORK_MASK includes SYSCALL_TRACE, but we don't need it.
- * SYSCALL_TRACE is anways seperately/unconditionally tested right after a
+ * SYSCALL_TRACE is anyway seperately/unconditionally tested right after a
* syscall, so all that reamins to be tested is _TIF_WORK_MASK
*/
#define __kernel_ok (segment_eq(get_fs(), KERNEL_DS))
/*
- * Algorthmically, for __user_ok() we want do:
+ * Algorithmically, for __user_ok() we want do:
* (start < TASK_SIZE) && (start+len < TASK_SIZE)
* where TASK_SIZE could either be retrieved from thread_info->addr_limit or
* emitted directly in code.
__tmp ^ __in; \
})
-#elif (ARC_BSWAP_TYPE == 2) /* Custom single cycle bwap instruction */
+#elif (ARC_BSWAP_TYPE == 2) /* Custom single cycle bswap instruction */
#define __arch_swab32(x) \
({ \
VECTOR instr_service ; 0x10, Instrn Error (0x2)
; ******************** Device ISRs **********************
-#ifdef CONFIG_ARC_IRQ3_LV2
-VECTOR handle_interrupt_level2
-#else
-VECTOR handle_interrupt_level1
-#endif
-
-VECTOR handle_interrupt_level1
-
-#ifdef CONFIG_ARC_IRQ5_LV2
-VECTOR handle_interrupt_level2
-#else
-VECTOR handle_interrupt_level1
-#endif
-
-#ifdef CONFIG_ARC_IRQ6_LV2
+#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
VECTOR handle_interrupt_level2
#else
VECTOR handle_interrupt_level1
#endif
-.rept 25
+.rept 28
VECTOR handle_interrupt_level1 ; Other devices
.endr
{
int level_mask = 0;
- /* setup any high priority Interrupts (Level2 in ARCompact jargon) */
- level_mask |= IS_ENABLED(CONFIG_ARC_IRQ3_LV2) << 3;
- level_mask |= IS_ENABLED(CONFIG_ARC_IRQ5_LV2) << 5;
- level_mask |= IS_ENABLED(CONFIG_ARC_IRQ6_LV2) << 6;
+ /* Is timer high priority Interrupt (Level2 in ARCompact jargon) */
+ level_mask |= IS_ENABLED(CONFIG_ARC_COMPACT_IRQ_LEVELS) << TIMER0_IRQ;
/*
* Write to register, even if no LV2 IRQs configured to reset it
int64_t delta = new_raw_count - prev_raw_count;
/*
- * We don't afaraid of hwc->prev_count changing beneath our feet
+ * We aren't afraid of hwc->prev_count changing beneath our feet
* because there's no way for us to re-enter this function anytime.
*/
local64_set(&hwc->prev_count, new_raw_count);
/*
* If we are here, it is established that @uboot_arg didn't
* point to DT blob. Instead if u-boot says it is cmdline,
- * Appent to embedded DT cmdline.
+ * append to embedded DT cmdline.
* setup_machine_fdt() would have populated @boot_command_line
*/
if (uboot_tag == 1) {
* -ViXS were still seeing crashes when using insmod to load drivers.
* It turned out that the code to change Execute permssions for TLB entries
* of user was not guarded for interrupts (mod_tlb_permission)
- * This was cauing TLB entries to be overwritten on unrelated indexes
+ * This was causing TLB entries to be overwritten on unrelated indexes
*
* Vineetg: July 15th 2008: Bug #94183
* -Exception happens in Delay slot of a JMP, and before user space resumes,
return 0;
}
-/* called on user read(): display the couters */
+/* called on user read(): display the counters */
static ssize_t tlb_stats_output(struct file *file, /* file descriptor */
char __user *user_buf, /* user buffer */
size_t len, /* length of buffer */
* ------------------
* This ver of MMU supports variable page sizes (1k-16k): although Linux will
* only support 8k (default), 16k and 4k.
- * However from hardware perspective, smaller page sizes aggrevate aliasing
+ * However from hardware perspective, smaller page sizes aggravate aliasing
* meaning more vaddr bits needed to disambiguate the cache-line-op ;
* the existing scheme of piggybacking won't work for certain configurations.
* Two new registers IC_PTAG and DC_PTAG inttoduced.
/*
* This is technically for MMU v4, using the MMU v3 programming model
- * Special work for HS38 aliasing I-cache configuratino with PAE40
+ * Special work for HS38 aliasing I-cache configuration with PAE40
* - upper 8 bits of paddr need to be written into PTAG_HI
* - (and needs to be written before the lower 32 bits)
* Note that PTAG_HI is hoisted outside the line loop
ic->ver, CONFIG_ARC_MMU_VER);
/*
- * In MMU v4 (HS38x) the alising icache config uses IVIL/PTAG
+ * In MMU v4 (HS38x) the aliasing icache config uses IVIL/PTAG
* pair to provide vaddr/paddr respectively, just as in MMU v3
*/
if (is_isa_arcv2() && ic->alias)
* DMA Coherent API Notes
*
* I/O is inherently non-coherent on ARC. So a coherent DMA buffer is
- * implemented by accessintg it using a kernel virtual address, with
+ * implemented by accessing it using a kernel virtual address, with
* Cache bit off in the TLB entry.
*
* The default DMA address == Phy address which is 0x8000_0000 based.