drm/radeon: fix PLLs on RS880 and older v2

commit 72edd83cc9e5819ed1ee771519143d7594e059f0 upstream.

This is a workaround for RS880 and older chips which seem to have
an additional limit on the minimum PLL input frequency.

v2: fix signed/unsigned warning

bugs:
https://bugzilla.kernel.org/show_bug.cgi?id=91861
https://bugzilla.kernel.org/show_bug.cgi?id=83461

Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 00ead8c2758a972debddf97234e206d211db5d7a..2e1e9aa79ceaca9997a610ba3e9a7e12d3a5ccf8 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -959,6 +959,9 @@ void radeon_compute_pll_avivo(struct radeon_pll *pll,
        if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV &&
            pll->flags & RADEON_PLL_USE_REF_DIV)
                ref_div_max = pll->reference_div;
+       else if (pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP)
+               /* fix for problems on RS880 */
+               ref_div_max = min(pll->max_ref_div, 7u);
        else
                ref_div_max = pll->max_ref_div;