diff options
| -rw-r--r-- | arch/arm/mach-mvebu/coherency.c | 44 |
1 files changed, 30 insertions, 14 deletions
diff --git a/arch/arm/mach-mvebu/coherency.c b/arch/arm/mach-mvebu/coherency.c index 044b511..c31f4c0 100644 --- a/arch/arm/mach-mvebu/coherency.c +++ b/arch/arm/mach-mvebu/coherency.c @@ -361,25 +361,41 @@ static int coherency_type(void) { struct device_node *np; const struct of_device_id *match; + int type; - np = of_find_matching_node_and_match(NULL, of_coherency_table, &match); - if (np) { - int type = (int) match->data; + /* + * The coherency fabric is needed: + * - For coherency between processors on Armada XP, so only + * when SMP is enabled. + * - For coherency between the processor and I/O devices, but + * this coherency requires many pre-requisites (write + * allocate cache policy, shareable pages, SMP bit set) that + * are only meant in SMP situations. + * + * Note that this means that on Armada 370, there is currently + * no way to use hardware I/O coherency, because even when + * CONFIG_SMP is enabled, is_smp() returns false due to the + * Armada 370 being a single-core processor. To lift this + * limitation, we would have to find a way to make the cache + * policy set to write-allocate (on all Armada SoCs), and to + * set the shareable attribute in page tables (on all Armada + * SoCs except the Armada 370). Unfortunately, such decisions + * are taken very early in the kernel boot process, at a point + * where we don't know yet on which SoC we are running. - /* Armada 370/XP coherency works in both UP and SMP */ - if (type == COHERENCY_FABRIC_TYPE_ARMADA_370_XP) - return type; + */ + if (!is_smp()) + return COHERENCY_FABRIC_TYPE_NONE; - /* Armada 375 coherency works only on SMP */ - else if (type == COHERENCY_FABRIC_TYPE_ARMADA_375 && is_smp()) - return type; + np = of_find_matching_node_and_match(NULL, of_coherency_table, &match); + if (!np) + return COHERENCY_FABRIC_TYPE_NONE; - /* Armada 380 coherency works only on SMP */ - else if (type == COHERENCY_FABRIC_TYPE_ARMADA_380 && is_smp()) - return type; - } + type = (int) match->data; + + of_node_put(np); - return COHERENCY_FABRIC_TYPE_NONE; + return type; } int coherency_available(void) |