From 0cefff963bf2af9ec9b2e2b537c3d3e6a43ceb9b Mon Sep 17 00:00:00 2001 From: Philippe CORNU Date: Tue, 17 Apr 2018 13:40:26 +0200 Subject: [PATCH] drm/stm: ltdc: add mode_valid() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add mode_valid() function to filter modes according to available pll clock values and "preferred" modes. It is particularly useful for hdmi modes that require precise pixel clocks. Note that "preferred" modes are always accepted: - 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. Signed-off-by: Philippe Cornu Reviewed-by: Yannick Fertré Link: https://patchwork.freedesktop.org/patch/msgid/20180417114026.8709-1-philippe.cornu@st.com --- drivers/gpu/drm/stm/ltdc.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) 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, -- 2.39.5