diff options
Diffstat (limited to 'drivers/gpu/drm/stm/ltdc.c')
| -rw-r--r-- | drivers/gpu/drm/stm/ltdc.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c index 014cef8cef37..616191fe98ae 100644 --- a/drivers/gpu/drm/stm/ltdc.c +++ b/drivers/gpu/drm/stm/ltdc.c @@ -445,6 +445,43 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc, reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR); } +#define CLK_TOLERANCE_HZ 50 + +static enum drm_mode_status +ltdc_crtc_mode_valid(struct drm_crtc *crtc, + const struct drm_display_mode *mode) +{ + struct ltdc_device *ldev = crtc_to_ltdc(crtc); + int target = mode->clock * 1000; + int target_min = target - CLK_TOLERANCE_HZ; + int target_max = target + CLK_TOLERANCE_HZ; + int result; + + /* + * Accept all "preferred" modes: + * - this is important for panels because panel clock tolerances are + * bigger than hdmi ones and there is no reason to not accept them + * (the fps may vary a little but it is not a problem). + * - the hdmi preferred mode will be accepted too, but userland will + * be able to use others hdmi "valid" modes if necessary. + */ + if (mode->type & DRM_MODE_TYPE_PREFERRED) + return MODE_OK; + + result = clk_round_rate(ldev->pixel_clk, target); + + DRM_DEBUG_DRIVER("clk rate target %d, available %d\n", target, result); + + /* + * Filter modes according to the clock value, particularly useful for + * hdmi modes that require precise pixel clocks. + */ + if (result < target_min || result > target_max) + return MODE_CLOCK_RANGE; + + return MODE_OK; +} + static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc, const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode) @@ -559,6 +596,7 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc, } static const struct drm_crtc_helper_funcs ltdc_crtc_helper_funcs = { + .mode_valid = ltdc_crtc_mode_valid, .mode_fixup = ltdc_crtc_mode_fixup, .mode_set_nofb = ltdc_crtc_mode_set_nofb, .atomic_flush = ltdc_crtc_atomic_flush, |