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Subject[PATCH 3/3] ARC: cache: allow to autodetect L1 cache line size
Date
One step to "build once run anywhere"

Allow to autodetect L1 I/D caches line size in runtime instead of
relying on value provided via Kconfig.

This is controlled via CONFIG_ARC_CACHE_LINE_AUTODETECT Kconfig option
which is disabled by default.
* In case of this option disabled there is no overhead in compare with
current implementation.
* In case of this option enabled there is some overhead in both speed
and code size:
- we use cache line size stored in the global variable instead of
compile time available define, so compiler can't do some
optimizations.
- we align all cache related buffers by maximum possible cache line
size. Nevertheless it isn't significant because we mostly use
SMP_CACHE_BYTES or ARCH_DMA_MINALIGN to align stuff (they are
equal to maximum possible cache line size)

Main change is the split L1_CACHE_BYTES for two separate defines:
* L1_CACHE_BYTES >= real L1 I$/D$ line size.
Available at compile time. Used for alligning stuff.
* CACHEOPS_L1_LINE_SZ == real L1 I$/D$ line size.
Available at run time. Used in operations with cache lines/regions.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
arch/arc/Kconfig | 10 +++++
arch/arc/include/asm/cache.h | 9 ++++-
arch/arc/lib/memset-archs.S | 8 +++-
arch/arc/mm/cache.c | 89 ++++++++++++++++++++++++++++++++++----------
4 files changed, 94 insertions(+), 22 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index c781e45d1d99..e7eb5ff1485d 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -215,10 +215,20 @@ menuconfig ARC_CACHE

if ARC_CACHE

+config ARC_CACHE_LINE_AUTODETECT
+ bool "Detect cache lines length automatically in runtime"
+ depends on ARC_HAS_ICACHE || ARC_HAS_DCACHE
+ help
+ ARC has configurable cache line length. Enable this option to detect
+ all cache lines length automatically in runtime to make kernel image
+ runnable on HW with different cache lines configuration.
+ If you don't know what the above means, leave this setting alone.
+
config ARC_CACHE_LINE_SHIFT
int "Cache Line Length (as power of 2)"
range 5 7
default "6"
+ depends on !ARC_CACHE_LINE_AUTODETECT
help
Starting with ARC700 4.9, Cache line length is configurable,
This option specifies "N", with Line-len = 2 power N
diff --git a/arch/arc/include/asm/cache.h b/arch/arc/include/asm/cache.h
index f1642634aab0..0ff8e19008e4 100644
--- a/arch/arc/include/asm/cache.h
+++ b/arch/arc/include/asm/cache.h
@@ -15,15 +15,22 @@
#define SMP_CACHE_BYTES ARC_MAX_CACHE_BYTES
#define ARCH_DMA_MINALIGN ARC_MAX_CACHE_BYTES

+#if IS_ENABLED(CONFIG_ARC_CACHE_LINE_AUTODETECT)
+/*
+ * This must be used for aligning only. In case of cache line autodetect it is
+ * only safe to use maximum possible value here.
+ */
+#define L1_CACHE_SHIFT ARC_MAX_CACHE_SHIFT
+#else
/* In case $$ not config, setup a dummy number for rest of kernel */
#ifndef CONFIG_ARC_CACHE_LINE_SHIFT
#define L1_CACHE_SHIFT 6
#else
#define L1_CACHE_SHIFT CONFIG_ARC_CACHE_LINE_SHIFT
#endif
+#endif /* IS_ENABLED(CONFIG_ARC_CACHE_LINE_AUTODETECT) */

#define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
-#define CACHE_LINE_MASK (~(L1_CACHE_BYTES - 1))

/*
* ARC700 doesn't cache any access in top 1G (0xc000_0000 to 0xFFFF_FFFF)
diff --git a/arch/arc/lib/memset-archs.S b/arch/arc/lib/memset-archs.S
index b3373f5c88e0..4baeeea29482 100644
--- a/arch/arc/lib/memset-archs.S
+++ b/arch/arc/lib/memset-archs.S
@@ -16,9 +16,15 @@
* line lengths (32B and 128B) you should rewrite code carefully checking
* we don't call any prefetchw/prealloc instruction for L1 cache lines which
* don't belongs to memset area.
+ *
+ * TODO: FIXME: as for today we chose not optimized memset implementation if we
+ * enable ARC_CACHE_LINE_AUTODETECT option (as we don't know L1 cache line
+ * size in compile time).
+ * One possible way to fix this is to declare memset as a function pointer and
+ * update it when we discover actual cache line size.
*/

-#if L1_CACHE_SHIFT == 6
+#if (!IS_ENABLED(CONFIG_ARC_CACHE_LINE_AUTODETECT)) && (L1_CACHE_SHIFT == 6)

.macro PREALLOC_INSTR reg, off
prealloc [\reg, \off]
diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 1036bd56f518..8d006c1d12a1 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -25,6 +25,22 @@
#define USE_RGN_FLSH 1
#endif

+/*
+ * Cache line defines and real L1 I$/D$ line size relations:
+ *
+ * L1_CACHE_BYTES >= real L1 I$/D$ line size. Available at compile time.
+ * CACHEOPS_L1_LINE_SZ == real L1 I$/D$ line size. Available at run time.
+ */
+#if IS_ENABLED(CONFIG_ARC_CACHE_LINE_AUTODETECT)
+#define CACHEOPS_L1_LINE_SZ l1_line_sz
+#define CACHEOPS_L1_LINE_MASK l1_line_mask
+#else
+#define CACHEOPS_L1_LINE_SZ L1_CACHE_BYTES
+#define CACHEOPS_L1_LINE_MASK (~((CACHEOPS_L1_LINE_SZ) - 1))
+#endif /* IS_ENABLED(CONFIG_ARC_CACHE_LINE_AUTODETECT) */
+
+static unsigned int l1_line_sz;
+static unsigned long l1_line_mask;
static int l2_line_sz;
static int ioc_exists;
int slc_enable = 1, ioc_enable = 1;
@@ -256,19 +272,19 @@ void __cache_line_loop_v2(phys_addr_t paddr, unsigned long vaddr,
* -@sz will be integral multiple of line size (being page sized).
*/
if (!full_page) {
- sz += paddr & ~CACHE_LINE_MASK;
- paddr &= CACHE_LINE_MASK;
- vaddr &= CACHE_LINE_MASK;
+ sz += paddr & ~CACHEOPS_L1_LINE_MASK;
+ paddr &= CACHEOPS_L1_LINE_MASK;
+ vaddr &= CACHEOPS_L1_LINE_MASK;
}

- num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);
+ num_lines = DIV_ROUND_UP(sz, CACHEOPS_L1_LINE_SZ);

/* MMUv2 and before: paddr contains stuffed vaddrs bits */
paddr |= (vaddr >> PAGE_SHIFT) & 0x1F;

while (num_lines-- > 0) {
write_aux_reg(aux_cmd, paddr);
- paddr += L1_CACHE_BYTES;
+ paddr += CACHEOPS_L1_LINE_SZ;
}
}

@@ -302,11 +318,11 @@ void __cache_line_loop_v3(phys_addr_t paddr, unsigned long vaddr,
* -@sz will be integral multiple of line size (being page sized).
*/
if (!full_page) {
- sz += paddr & ~CACHE_LINE_MASK;
- paddr &= CACHE_LINE_MASK;
- vaddr &= CACHE_LINE_MASK;
+ sz += paddr & ~CACHEOPS_L1_LINE_MASK;
+ paddr &= CACHEOPS_L1_LINE_MASK;
+ vaddr &= CACHEOPS_L1_LINE_MASK;
}
- num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);
+ num_lines = DIV_ROUND_UP(sz, CACHEOPS_L1_LINE_SZ);

/*
* MMUv3, cache ops require paddr in PTAG reg
@@ -328,11 +344,11 @@ void __cache_line_loop_v3(phys_addr_t paddr, unsigned long vaddr,
while (num_lines-- > 0) {
if (!full_page) {
write_aux_reg(aux_tag, paddr);
- paddr += L1_CACHE_BYTES;
+ paddr += CACHEOPS_L1_LINE_SZ;
}

write_aux_reg(aux_cmd, vaddr);
- vaddr += L1_CACHE_BYTES;
+ vaddr += CACHEOPS_L1_LINE_SZ;
}
}

@@ -372,11 +388,11 @@ void __cache_line_loop_v4(phys_addr_t paddr, unsigned long vaddr,
* -@sz will be integral multiple of line size (being page sized).
*/
if (!full_page) {
- sz += paddr & ~CACHE_LINE_MASK;
- paddr &= CACHE_LINE_MASK;
+ sz += paddr & ~CACHEOPS_L1_LINE_MASK;
+ paddr &= CACHEOPS_L1_LINE_MASK;
}

- num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);
+ num_lines = DIV_ROUND_UP(sz, CACHEOPS_L1_LINE_SZ);

/*
* For HS38 PAE40 configuration
@@ -396,7 +412,7 @@ void __cache_line_loop_v4(phys_addr_t paddr, unsigned long vaddr,

while (num_lines-- > 0) {
write_aux_reg(aux_cmd, paddr);
- paddr += L1_CACHE_BYTES;
+ paddr += CACHEOPS_L1_LINE_SZ;
}
}

@@ -422,14 +438,14 @@ void __cache_line_loop_v4(phys_addr_t paddr, unsigned long vaddr,

if (!full_page) {
/* for any leading gap between @paddr and start of cache line */
- sz += paddr & ~CACHE_LINE_MASK;
- paddr &= CACHE_LINE_MASK;
+ sz += paddr & ~CACHEOPS_L1_LINE_MASK;
+ paddr &= CACHEOPS_L1_LINE_MASK;

/*
* account for any trailing gap to end of cache line
* this is equivalent to DIV_ROUND_UP() in line ops above
*/
- sz += L1_CACHE_BYTES - 1;
+ sz += CACHEOPS_L1_LINE_SZ - 1;
}

if (is_pae40_enabled()) {
@@ -1215,14 +1231,21 @@ static void arc_l1_line_check(unsigned int line_len, const char *cache_name)
panic("%s support enabled but non-existent cache\n",
cache_name);

- if (line_len != L1_CACHE_BYTES)
+ /*
+ * In case of CONFIG_ARC_CACHE_LINE_AUTODETECT disabled we check
+ * that cache line size is equal to provided via Kconfig,
+ * in case of CONFIG_ARC_CACHE_LINE_AUTODETECT enabled we check
+ * that cache line size is equal for every L1 (I/D) cache on every cpu.
+ */
+ if (line_len != CACHEOPS_L1_LINE_SZ)
panic("%s line size [%u] != expected [%u]",
- cache_name, line_len, L1_CACHE_BYTES);
+ cache_name, line_len, CACHEOPS_L1_LINE_SZ);
}
#endif /* IS_ENABLED(CONFIG_ARC_HAS_ICACHE) || IS_ENABLED(CONFIG_ARC_HAS_DCACHE) */

/*
* Cache related boot time checks needed on every CPU.
+ * NOTE: This function expects 'l1_line_sz' to be set.
*/
static void arc_l1_cache_check(unsigned int cpu)
{
@@ -1239,12 +1262,28 @@ static void arc_l1_cache_check(unsigned int cpu)
* configuration (we validate this in arc_cache_check()):
* - Geometry checks
* - L1 cache line loop callbacks
+ * - l1_line_sz / l1_line_mask setup
*/
void __init arc_l1_cache_init_master(unsigned int cpu)
{
+ /*
+ * 'l1_line_sz' programing model:
+ * We simplify programing of 'l1_line_sz' as we assume that we don't
+ * support case where CPU have different cache configuration.
+ * 1. Assign to 'l1_line_sz' length of any (I/D) L1 cache line of
+ * master CPU.
+ * 2. Validate 'l1_line_sz' length itself.
+ * 3. Check that both L1 I$/D$ lines on each CPU are equal to
+ * 'l1_line_sz' (or to value provided via Kconfig in case of
+ * CONFIG_ARC_CACHE_LINE_AUTODETECT is disabled). This is done in
+ * arc_cache_check() which is called for each CPU.
+ */
+
if (IS_ENABLED(CONFIG_ARC_HAS_ICACHE)) {
struct cpuinfo_arc_cache *ic = &cpuinfo_arc700[cpu].icache;

+ l1_line_sz = ic->line_len;
+
/*
* In MMU v4 (HS38x) the aliasing icache config uses IVIL/PTAG
* pair to provide vaddr/paddr respectively, just as in MMU v3
@@ -1258,6 +1297,8 @@ void __init arc_l1_cache_init_master(unsigned int cpu)
if (IS_ENABLED(CONFIG_ARC_HAS_DCACHE)) {
struct cpuinfo_arc_cache *dc = &cpuinfo_arc700[cpu].dcache;

+ l1_line_sz = dc->line_len;
+
/* check for D-Cache aliasing on ARCompact: ARCv2 has PIPT */
if (is_isa_arcompact()) {
int handled = IS_ENABLED(CONFIG_ARC_CACHE_VIPT_ALIASING);
@@ -1274,6 +1315,14 @@ void __init arc_l1_cache_init_master(unsigned int cpu)
}
}

+ if (IS_ENABLED(CONFIG_ARC_HAS_ICACHE) ||
+ IS_ENABLED(CONFIG_ARC_HAS_DCACHE)) {
+ if (l1_line_sz != 32 && l1_line_sz != 64 && l1_line_sz != 128)
+ panic("L1 cache line sz [%u] unsupported\n", l1_line_sz);
+
+ l1_line_mask = ~(l1_line_sz - 1);
+ }
+
/*
* Check that SMP_CACHE_BYTES (and hence ARCH_DMA_MINALIGN) is larger
* or equal to any cache line length.
--
2.14.5
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