Re: [PATCH 10/13] cpufreq: powernow-k8: Make use of known set but not used variables

On Tue, 14 Jul 2020, Rafael J. Wysocki wrote:

On Tue, Jul 14, 2020 at 4:51 PM Lee Jones [off-list ref] wrote:

quoted

If we fail to use a variable, even a 'dummy' one, then the compiler
complains that it is set but not used.  We know this is fine, so we
set it to its own value here.

Fixes the following W=1 kernel build warning(s):

 drivers/cpufreq/powernow-k8.c: In function ‘pending_bit_stuck’:
 drivers/cpufreq/powernow-k8.c:89:10: warning: variable ‘hi’ set but not used [-Wunused-but-set-variable]
 89 | u32 lo, hi;
 | ^~
 drivers/cpufreq/powernow-k8.c: In function ‘core_voltage_pre_transition’:
 drivers/cpufreq/powernow-k8.c:285:14: warning: variable ‘lo’ set but not used [-Wunused-but-set-variable]
 285 | u32 maxvid, lo, rvomult = 1;
 | ^~

Cc: Andreas Herrmann <redacted>
Cc: Dominik Brodowski <redacted>
Cc: Pavel Machek <redacted>
Cc: Paul Devriendt <redacted>
Cc: Mark Langsdorf <redacted>
Signed-off-by: Lee Jones <redacted>
---
 drivers/cpufreq/powernow-k8.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index 3984959eed1d5..b76df81044c4f 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c

@@ -89,6 +89,7 @@ static int pending_bit_stuck(void)
        u32 lo, hi;

        rdmsr(MSR_FIDVID_STATUS, lo, hi);
+       hi &= hi; /* Silence set but not used warning */

Hmm.

What about using __always_unused for this?

I didn't know you could use that for standard variables.

Will fix.

quoted

        return lo & MSR_S_LO_CHANGE_PENDING ? 1 : 0;
 }

@@ -292,6 +293,7 @@ static int core_voltage_pre_transition(struct powernow_k8_data *data,
                rvomult = 2;
        rvosteps *= rvomult;
        rdmsr(MSR_FIDVID_STATUS, lo, maxvid);
+       lo &= lo; /* Silence set but not used warning */
        maxvid = 0x1f & (maxvid >> 16);
        pr_debug("ph1 maxvid=0x%x\n", maxvid);
        if (reqvid < maxvid) /* lower numbers are higher voltages */

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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