drm/stm: ltdc: add mode_valid()

	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)

}

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,