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x86: mp: Add iterators for CPUs

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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 <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2020-07-17 08:48:21 -06:00 committed by Bin Meng
parent 99a573fb32
commit 0538d6833c
2 changed files with 105 additions and 0 deletions
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63
arch/x86/cpu/mp_init.c
View File

@ -684,6 +684,69 @@ int mp_park_aps(void)
return 0;
}
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 (!IS_ENABLED(CONFIG_SMP_AP_WORK) || 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;

42
arch/x86/include/asm/mp.h
View File

@ -118,6 +118,33 @@ int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg);
* @return 0 if OK, -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)
{
@ -134,6 +161,21 @@ 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_ */