[RFC][PATCH 2/2] drm: kirin: Restrict modes to known good mode clocks

[John Stultz]

Currently the hikey dsi logic cannot generate accurate byte
clocks values for all pixel clock values. Thus if a mode clock
is selected that cannot match the calculated byte clock, the
device will boot with a blank screen.

This patch uses the new mode_valid callback to enforces known
good mode clocks for well known resolutions, which should allow
the display to work from given EDID options, and ensures for a
given resolution & refresh, the right mode clock is selected.

Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Sean Paul <seanpaul at chromium.org>
Cc: David Airlie <airlied at linux.ie>
Cc: Rob Clark <robdclark at gmail.com>
Cc: Xinliang Liu <xinliang.liu at linaro.org>
Cc: Xinliang Liu <z.liuxinliang at hisilicon.com>
Cc: Rongrong Zou <zourongrong at gmail.com>
Cc: Xinwei Kong <kong.kongxinwei at hisilicon.com>
Cc: Chen Feng <puck.chen at hisilicon.com>
Cc: Archit Taneja <architt at codeaurora.org>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: John Stultz <john.stultz at linaro.org>
---
 drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c | 38 +++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
index afc2b5d..9161633 100644
--- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
+++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c
@@ -504,6 +504,43 @@ static void ade_crtc_disable(struct drm_crtc *crtc)
 	acrtc->enable = false;
 }
 
+static enum drm_mode_status ade_crtc_mode_valid(struct drm_crtc *crtc,
+						struct drm_display_mode *mode)
+{
+	/*
+	 * kirin_ade cannot generate all modes, so use the whitelist below
+	 */
+	DRM_DEBUG("Checking mode %ix%i@%i clock: %i...",
+		  mode->hdisplay, mode->vdisplay, drm_mode_vrefresh(mode), mode->clock);
+	if ((mode->hdisplay == 1920 && mode->vdisplay == 1080 && mode->clock == 148500) ||
+	    (mode->hdisplay == 1920 && mode->vdisplay == 1080 && mode->clock == 80192)  ||
+	    (mode->hdisplay == 1920 && mode->vdisplay == 1080 && mode->clock == 74250)  ||
+	    (mode->hdisplay == 1920 && mode->vdisplay == 1080 && mode->clock == 61855)  ||
+	    (mode->hdisplay == 1680 && mode->vdisplay == 1050 && mode->clock == 147116) ||
+	    (mode->hdisplay == 1680 && mode->vdisplay == 1050 && mode->clock == 146250) ||
+	    (mode->hdisplay == 1680 && mode->vdisplay == 1050 && mode->clock == 144589) ||
+	    (mode->hdisplay == 1600 && mode->vdisplay == 1200 && mode->clock == 160961) ||
+	    (mode->hdisplay == 1600 && mode->vdisplay == 900  && mode->clock == 118963) ||
+	    (mode->hdisplay == 1440 && mode->vdisplay == 900  && mode->clock == 126991) ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 1024 && mode->clock == 128946) ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 1024 && mode->clock == 98619)  ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 960  && mode->clock == 102081) ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 800  && mode->clock == 83496)  ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 720  && mode->clock == 74440)  ||
+	    (mode->hdisplay == 1280 && mode->vdisplay == 720  && mode->clock == 74250)  ||
+	    (mode->hdisplay == 1024 && mode->vdisplay == 768  && mode->clock == 78800)  ||
+	    (mode->hdisplay == 1024 && mode->vdisplay == 768  && mode->clock == 75000)  ||
+	    (mode->hdisplay == 1024 && mode->vdisplay == 768  && mode->clock == 81833)  ||
+	    (mode->hdisplay == 800  && mode->vdisplay == 600  && mode->clock == 48907)  ||
+	    (mode->hdisplay == 800  && mode->vdisplay == 600  && mode->clock == 40000)) {
+		mode->type |= DRM_MODE_TYPE_PREFERRED;
+		DRM_DEBUG("OK\n");
+		return MODE_OK;
+	}
+	DRM_DEBUG("BAD\n");
+	return MODE_BAD;
+}
+
 static void ade_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct ade_crtc *acrtc = to_ade_crtc(crtc);
@@ -557,6 +594,7 @@ static void ade_crtc_atomic_flush(struct drm_crtc *crtc,
 static const struct drm_crtc_helper_funcs ade_crtc_helper_funcs = {
 	.enable		= ade_crtc_enable,
 	.disable	= ade_crtc_disable,
+	.mode_valid	= ade_crtc_mode_valid,
 	.mode_set_nofb	= ade_crtc_mode_set_nofb,
 	.atomic_begin	= ade_crtc_atomic_begin,
 	.atomic_flush	= ade_crtc_atomic_flush,
-- 
2.7.4