It is convenient to iterate through the CPUs performing work on each one
and processing the result. Add a few iterator functions which handle this.
These can be used by any client code. It can call mp_run_on_cpus() on
each CPU that is returned, handling them one at a time.
Signed-off-by: Simon Glass <s...@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wall...@br-automation.com>
---
Changes in v3:
- Add more comments on how the iterators work
arch/x86/cpu/mp_init.c | 62 +++++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/mp.h | 42 ++++++++++++++++++++++++++
2 files changed, 104 insertions(+)
diff --git a/arch/x86/cpu/mp_init.c b/arch/x86/cpu/mp_init.c
index 0bf325ae88..d054563722 100644
--- a/arch/x86/cpu/mp_init.c
+++ b/arch/x86/cpu/mp_init.c
@@ -669,6 +669,68 @@ int mp_park_aps(void)
return get_timer(start);
}
+int mp_first_cpu(int cpu_select)
+{
+ struct udevice *dev;
+ int num_cpus;
+ int ret;
+
+ /*
+ * This assumes that CPUs are numbered from 0. This function tries to
+ * avoid assuming the CPU 0 is the boot CPU
+ */
+ if (cpu_select == MP_SELECT_ALL)
+ return 0; /* start with the first one */
+
+ ret = get_bsp(&dev, &num_cpus);
+ if (ret < 0)
+ return log_msg_ret("bsp", ret);
+
+ /* Return boot CPU if requested */
+ if (cpu_select == MP_SELECT_BSP)
+ return ret;
+
+ /* Return something other than the boot CPU, if APs requested */
+ if (cpu_select == MP_SELECT_APS && num_cpus > 1)
+ return ret == 0 ? 1 : 0;
+
+ /* Try to check for an invalid value */
+ if (cpu_select < 0 || cpu_select >= num_cpus)
+ return -EINVAL;
+
+ return cpu_select; /* return the only selected one */
+}
+
+int mp_next_cpu(int cpu_select, int prev_cpu)
+{
+ struct udevice *dev;
+ int num_cpus;
+ int ret;
+ int bsp;
+
+ /* If we selected the BSP or a particular single CPU, we are done */
+ if (cpu_select == MP_SELECT_BSP || cpu_select >= 0)
+ return -EFBIG;
+
+ /* Must be doing MP_SELECT_ALL or MP_SELECT_APS; return the next CPU */
+ ret = get_bsp(&dev, &num_cpus);
+ if (ret < 0)
+ return log_msg_ret("bsp", ret);
+ bsp = ret;
+
+ /* Move to the next CPU */
+ assert(prev_cpu >= 0);
+ ret = prev_cpu + 1;
+
+ /* Skip the BSP if needed */
+ if (cpu_select == MP_SELECT_APS && ret == bsp)
+ ret++;
+ if (ret >= num_cpus)
+ return -EFBIG;
+
+ return ret;
+}
+
int mp_init(void)
{
int num_aps, num_cpus;
diff --git a/arch/x86/include/asm/mp.h b/arch/x86/include/asm/mp.h
index 4acce55b8c..cec790b32b 100644
--- a/arch/x86/include/asm/mp.h
+++ b/arch/x86/include/asm/mp.h
@@ -115,6 +115,33 @@ int mp_run_on_cpus(int cpu_select, mp_run_func func, void
*arg);
* @return time taken to park the APs on success (in microseconds), -ve on
error
*/
int mp_park_aps(void);
+
+/**
+ * mp_first_cpu() - Get the first CPU to process, from a selection
+ *
+ * This is used to iterate through selected CPUs. Call this function first,
then
+ * call mp_next_cpu() repeatedly (with the same @cpu_select) until it returns
+ * -EFBIG.
+ *
+ * @cpu_select: Selected CPUs (either a CPU number or MP_SELECT_...)
+ * @return next CPU number to run on (e.g. 0)
+ */
+int mp_first_cpu(int cpu_select);
+
+/**
+ * mp_next_cpu() - Get the next CPU to process, from a selection
+ *
+ * This is used to iterate through selected CPUs. After first calling
+ * mp_first_cpu() once, call this function repeatedly until it returns -EFBIG.
+ *
+ * The value of @cpu_select must be the same for all calls and must match the
+ * value passed to mp_first_cpu(), otherwise the behaviour is undefined.
+ *
+ * @cpu_select: Selected CPUs (either a CPU number or MP_SELECT_...)
+ * @prev_cpu: Previous value returned by mp_first_cpu()/mp_next_cpu()
+ * @return next CPU number to run on (e.g. 0)
+ */
+int mp_next_cpu(int cpu_select, int prev_cpu);
#else
static inline int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg)
{
@@ -131,6 +158,21 @@ static inline int mp_park_aps(void)
return 0;
}
+static inline int mp_first_cpu(int cpu_select)
+{
+ /* We cannot run on any APs, nor a selected CPU */
+ return cpu_select == MP_SELECT_APS ? -EFBIG : MP_SELECT_BSP;
+}
+
+static inline int mp_next_cpu(int cpu_select, int prev_cpu)
+{
+ /*
+ * When MP is not enabled, there is only one CPU and we did it in
+ * mp_first_cpu()
+ */
+ return -EFBIG;
+}
+
#endif
#endif /* _X86_MP_H_ */
--
2.27.0.212.ge8ba1cc988-goog
