On 13 May 2014 16:28, Dave Martin [off-list ref] wrote:

On Sun, May 11, 2014 at 04:06:02PM +0800, Haojian Zhuang wrote:

quoted

Multiple CPU clusters are used in Hisilicon HiP04 SoC. Now use MCPM
framework to manage power on HiP04 SoC.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
---
 arch/arm/mach-hisi/Makefile   |   1 +
 arch/arm/mach-hisi/platmcpm.c | 309 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 310 insertions(+)
 create mode 100644 arch/arm/mach-hisi/platmcpm.c

diff --git a/arch/arm/mach-hisi/Makefile b/arch/arm/mach-hisi/Makefile
index 2ae1b59..e7a8640 100644
--- a/arch/arm/mach-hisi/Makefile
+++ b/arch/arm/mach-hisi/Makefile

@@ -3,4 +3,5 @@
 #

 obj-y        += hisilicon.o
+obj-$(CONFIG_MCPM)           += platmcpm.o
 obj-$(CONFIG_SMP)            += platsmp.o hotplug.o

diff --git a/arch/arm/mach-hisi/platmcpm.c b/arch/arm/mach-hisi/platmcpm.c
new file mode 100644
index 0000000..6208bc6
--- /dev/null
+++ b/arch/arm/mach-hisi/platmcpm.c

@@ -0,0 +1,309 @@

[...]

quoted

+static int hip04_mcpm_power_up(unsigned int cpu, unsigned int cluster)
+{
+     unsigned long data, mask;
+
+     if (!relocation || !sysctrl)
+             return -ENODEV;
+     if (cluster >= HIP04_MAX_CLUSTERS || cpu >= HIP04_MAX_CPUS_PER_CLUSTER)
+             return -EINVAL;
+
+     spin_lock_irq(&boot_lock);
+     writel_relaxed(hip04_boot.bootwrapper_phys, relocation);
+     writel_relaxed(hip04_boot.bootwrapper_magic, relocation + 4);
+     writel_relaxed(virt_to_phys(mcpm_entry_point), relocation + 8);
+     writel_relaxed(0, relocation + 12);
+
+     if (hip04_cluster_down(cluster)) {
+             data = CLUSTER_DEBUG_RESET_BIT;
+             writel_relaxed(data, sysctrl + SC_CPU_RESET_DREQ(cluster));
+             do {
+                     mask = CLUSTER_DEBUG_RESET_STATUS;
+                     data = readl_relaxed(sysctrl + \
+                                          SC_CPU_RESET_STATUS(cluster));
+             } while (data & mask);
+             hip04_set_snoop_filter(cluster, 1);

Did you find the answer regarding whether it's safe to enable snoops to
a powered-down CPU?

Does HiP04 use CCI, or some different interconnect?  As Nico pointed out,
the above code would definitely not be safe for CCI.

First, it's safe.
In the second, HiP04 doesn't use CCI. They designed their own fabric instead.

Regards
Haojian