gpu: ipu-di: Add ipu_di_adjust_videomode()

On some monitors, high resolution modes are not working, exhibiting
pixel column truncation problems (for example, 1280x1024 displays as
1280x1022).

The function ipu_di_adjust_videomode() aims to fix these issues by
adjusting a passed videomode to IPU restrictions. The function can
be called from the drm_crtc_helper_funcs->mode_fixup() methods.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Deepak Das <deepak_das@mentor.com>
Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/gpu/ipu-v3/ipu-di.c b/drivers/gpu/ipu-v3/ipu-di.c
index c490ba4384fc..46f9570a8b59 100644
--- a/drivers/gpu/ipu-v3/ipu-di.c
+++ b/drivers/gpu/ipu-v3/ipu-di.c
@@ -511,6 +511,35 @@ static void ipu_di_config_clock(struct ipu_di *di,
                 clk_get_rate(di->clk_di_pixel) / (clkgen0 >> 4));
 }
 
+/*
+ * This function is called to adjust a video mode to IPU restrictions.
+ * It is meant to be called from drm crtc mode_fixup() methods.
+ */
+int ipu_di_adjust_videomode(struct ipu_di *di, struct videomode *mode)
+{
+        u32 diff;
+
+        if (mode->vfront_porch >= 2)
+                return 0;
+
+        diff = 2 - mode->vfront_porch;
+
+        if (mode->vback_porch >= diff) {
+                mode->vfront_porch = 2;
+                mode->vback_porch -= diff;
+        } else if (mode->vsync_len > diff) {
+                mode->vfront_porch = 2;
+                mode->vsync_len = mode->vsync_len - diff;
+        } else {
+                dev_warn(di->ipu->dev, "failed to adjust videomode\n");
+                return -EINVAL;
+        }
+
+        dev_warn(di->ipu->dev, "videomode adapted for IPU restrictions\n");
+        return 0;
+}
+EXPORT_SYMBOL_GPL(ipu_di_adjust_videomode);
+
 int ipu_di_init_sync_panel(struct ipu_di *di, struct ipu_di_signal_cfg *sig)
 {
         u32 reg;