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powernv-cpufreq: Add helper to extract pstate from PMSR 

On POWERNV platform, the fields for pstates in the Power Management
Status Register (PMSR) and the Power Management Control Register
(PMCR) are 8-bits wide. On POWER8 the pstates are negatively numbered
while on POWER9 they are positively numbered.

The device-tree exports pstates as 32-bit entries. The device-tree
implementation sign-extends the 8-bit pstate values to obtain the
corresponding 32-bit entry.

Eg: On POWER8, a pstate value 0x82 [-126] is represented in the
device-tree as 0xfffffff82 while on POWER9, the same value 0x82 [130]
is represented in the device-tree as 0x00000082.

The powernv-cpufreq driver implementation represents pstates using the
integer type. In multiple places in the driver, the code interprets
the pstates extracted from the PMSR as a signed byte and assigns it to
a integer variable to get the sign-extention.

On POWER9 platforms which have greater than 128 pstates, this results
in the driver performing incorrect sign-extention, and thereby
treating a legitimate pstate (say 130) as an invalid pstates (since it
is interpreted as -126).

This patch fixes the issue by implementing a helper function to
extract Pstates from PMSR register, and correctly sign-extend it to be
consistent with the values provided by the device-tree.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Gautham R. Shenoy 2017-12-13 12:27:39 +05:30 committed by Rafael J. Wysocki
parent 2332bd0419
commit ee1f4a7daf
1 changed files with 23 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/cpufreq/powernv-cpufreq.c
View File

@ -41,11 +41,9 @@
#define POWERNV_MAX_PSTATES 256
#define PMSR_PSAFE_ENABLE (1UL << 30)
#define PMSR_SPR_EM_DISABLE (1UL << 31)
#define PMSR_MAX(x) ((x >> 32) & 0xFF)
#define MAX_PSTATE_SHIFT 32
#define LPSTATE_SHIFT 48
#define GPSTATE_SHIFT 56
#define GET_LPSTATE(x) (((x) >> LPSTATE_SHIFT) & 0xFF)
#define GET_GPSTATE(x) (((x) >> GPSTATE_SHIFT) & 0xFF)
#define MAX_RAMP_DOWN_TIME 5120
/*
@ -94,6 +92,7 @@ struct global_pstate_info {
};
static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
u32 pstate_sign_prefix;
static bool rebooting, throttled, occ_reset;
static const char * const throttle_reason[] = {
@ -148,6 +147,20 @@ static struct powernv_pstate_info {
bool wof_enabled;
} powernv_pstate_info;
static inline int extract_pstate(u64 pmsr_val, unsigned int shift)
{
int ret = ((pmsr_val >> shift) & 0xFF);
if (!ret)
return ret;
return (pstate_sign_prefix | ret);
}
#define extract_local_pstate(x) extract_pstate(x, LPSTATE_SHIFT)
#define extract_global_pstate(x) extract_pstate(x, GPSTATE_SHIFT)
#define extract_max_pstate(x) extract_pstate(x, MAX_PSTATE_SHIFT)
/* Use following macros for conversions between pstate_id and index */
static inline int idx_to_pstate(unsigned int i)
{
@ -278,6 +291,9 @@ next:
powernv_pstate_info.nr_pstates = nr_pstates;
pr_debug("NR PStates %d\n", nr_pstates);
pstate_sign_prefix = pstate_min & ~0xFF;
for (i = 0; i < nr_pstates; i++) {
u32 id = be32_to_cpu(pstate_ids[i]);
u32 freq = be32_to_cpu(pstate_freqs[i]);
@ -438,17 +454,10 @@ struct powernv_smp_call_data {
static void powernv_read_cpu_freq(void *arg)
{
unsigned long pmspr_val;
s8 local_pstate_id;
struct powernv_smp_call_data *freq_data = arg;
pmspr_val = get_pmspr(SPRN_PMSR);
/*
* The local pstate id corresponds bits 48..55 in the PMSR.
* Note: Watch out for the sign!
*/
local_pstate_id = (pmspr_val >> 48) & 0xFF;
freq_data->pstate_id = local_pstate_id;
freq_data->pstate_id = extract_local_pstate(pmspr_val);
freq_data->freq = pstate_id_to_freq(freq_data->pstate_id);
pr_debug("cpu %d pmsr %016lX pstate_id %d frequency %d kHz\n",
@ -522,7 +531,7 @@ static void powernv_cpufreq_throttle_check(void *data)
chip = this_cpu_read(chip_info);
/* Check for Pmax Capping */
pmsr_pmax = (s8)PMSR_MAX(pmsr);
pmsr_pmax = extract_max_pstate(pmsr);
pmsr_pmax_idx = pstate_to_idx(pmsr_pmax);
if (pmsr_pmax_idx != powernv_pstate_info.max) {
if (chip->throttled)
@ -645,8 +654,8 @@ void gpstate_timer_handler(struct timer_list *t)
* value. Hence, read from PMCR to get correct data.
*/
val = get_pmspr(SPRN_PMCR);
freq_data.gpstate_id = (s8)GET_GPSTATE(val);
freq_data.pstate_id = (s8)GET_LPSTATE(val);
freq_data.gpstate_id = extract_global_pstate(val);
freq_data.pstate_id = extract_local_pstate(val);
if (freq_data.gpstate_id == freq_data.pstate_id) {
reset_gpstates(policy);
spin_unlock(&gpstates->gpstate_lock);