On Fri, Mar 04, 2022 at 01:03:55PM -0800, trix@redhat.com wrote:
From: Tom Rix trix@redhat.com
Clang static analysis reports this issue intel_dpll.c:472:31: warning: The left operand of '-' is a garbage value [core.UndefinedBinaryOperatorResult] this_err = abs(clock.dot - target); ~~~~~~~~~ ^
In a loop clock.dot is set on successful call to i9xx_calc_dpll_params(). If the call fails, the later *is_valid() will use the previous loop's clock.dot.
I don't think this can happen. intel_pll_is_valid() validates all the dividers first and bails out if they are junk.
The *_dpll_params functions return an arithmetic statement with the clock.dot as the variable. Change the error handler to set clock.dot to 0 and jump to the return statement.
Fixes: dccbea3b0704 ("drm/i915: calculate the port clock rate along with other PLL params") Signed-off-by: Tom Rix trix@redhat.com
drivers/gpu/drm/i915/display/intel_dpll.c | 32 ++++++++++++++--------- 1 file changed, 20 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dpll.c b/drivers/gpu/drm/i915/display/intel_dpll.c index 0ae37fdbf2a5b..ba7cada704288 100644 --- a/drivers/gpu/drm/i915/display/intel_dpll.c +++ b/drivers/gpu/drm/i915/display/intel_dpll.c @@ -309,11 +309,13 @@ int pnv_calc_dpll_params(int refclk, struct dpll *clock) { clock->m = clock->m2 + 2; clock->p = clock->p1 * clock->p2;
- if (WARN_ON(clock->n == 0 || clock->p == 0))
return 0;
- if (WARN_ON(clock->n == 0 || clock->p == 0)) {
clock->dot = 0;goto end;- } clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n); clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
+end: return clock->dot; }
@@ -326,11 +328,13 @@ int i9xx_calc_dpll_params(int refclk, struct dpll *clock) { clock->m = i9xx_dpll_compute_m(clock); clock->p = clock->p1 * clock->p2;
- if (WARN_ON(clock->n + 2 == 0 || clock->p == 0))
return 0;
- if (WARN_ON(clock->n + 2 == 0 || clock->p == 0)) {
clock->dot = 0;goto end;- } clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n + 2); clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
+end: return clock->dot; }
@@ -338,11 +342,13 @@ int vlv_calc_dpll_params(int refclk, struct dpll *clock) { clock->m = clock->m1 * clock->m2; clock->p = clock->p1 * clock->p2;
- if (WARN_ON(clock->n == 0 || clock->p == 0))
return 0;
- if (WARN_ON(clock->n == 0 || clock->p == 0)) {
clock->dot = 0;goto end;- } clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n); clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
+end: return clock->dot / 5; }
@@ -350,12 +356,14 @@ int chv_calc_dpll_params(int refclk, struct dpll *clock) { clock->m = clock->m1 * clock->m2; clock->p = clock->p1 * clock->p2;
- if (WARN_ON(clock->n == 0 || clock->p == 0))
return 0;
- if (WARN_ON(clock->n == 0 || clock->p == 0)) {
clock->dot = 0;goto end;- } clock->vco = DIV_ROUND_CLOSEST_ULL(mul_u32_u32(refclk, clock->m), clock->n << 22); clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p);
+end: return clock->dot / 5; }
-- 2.26.3