kernel 3.14, select display timings from command line

[angelo_d]

Dear all,

i have a imx6q board similar to sabreauto.

Generally i use a display type1 on LVDS0 and a display type2 on LVDS1.

But sometime i need to swap them.

In previous kernel version as 3.10.17, this was possible simply changing the kernel mxcfb resolutions in kernel cmdline params.

In kernel 3.14, a new devictree node has been added, and display timing and resolution need to be specified there.

But, when i switch the 2 displays i have now to change the device tree.

Is there any way to avoid this kernel / dts re-build ?

Thanks,

angelo

[angelo_d]

From what i realize from the sources, no.

I added a small patch to parse commandline for a parameter inside drivers/video/mxc/ldb.c.

I get an index to pass to of_get_videomode call.

Best regards

angelo

[alejandrolozan1]

Hi Angelo,

Would you be nice enough to share the patch you created? It would be very appreciated and helpful for future references.

Best Regards,

Alejandro

[angelo_d · Accepted solution]

Hi,

welcome

Patch body:
    add support for lvds timings set from command line
    Signed-off-by: Angelo Dureghello <angelo.dureghello@nomovok.com>
--------------------------- drivers/video/mxc/ldb.c ---------------------------
index d3e8494..ae49cf4 100644
@@ -391,7 +391,6 @@ static int ldb_setup(struct mxc_dispdrv_handle *mddh,
     struct ldb_chan chan;
     struct device *dev = ldb->dev;
     struct clk *ldb_di_parent, *ldb_di_sel, *ldb_di_sel_parent;
-    struct clk *other_ldb_di_sel = NULL;
     struct bus_mux bus_mux;
     int ret = 0, id = 0, chno, other_chno;
     unsigned long serial_clk;
@@ -680,6 +679,35 @@ static bool is_valid_crtc(struct ldb_data *ldb, enum crtc crtc,
     return false;
 }
+extern char *saved_command_line;
+
+#define ERR_NO_LVDS_TIMING   -1
+
+/*
+ * Nomovok OY
+ * we want the ability to select display timing from command line.
+ *
+ * use params:
+ *  lvds0_timing=index
+ *  lvds1_timing=index
+ *
+ * where index 0 is the first timing entry
+ *
+ */
+static int get_ldb_timing(int ch)
+{
+    char *x, *s = saved_command_line;
+    static char buff[16];
+
+    sprintf(buff, "lvds%d_timing=", ch);
+
+    if ((x = strstr(s, buff)) != NULL) {
+        return (x[13]-48);
+    }
+
+    return ERR_NO_LVDS_TIMING;
+}
+
 static int ldb_probe(struct platform_device *pdev)
 {
     struct device *dev = &pdev->dev;
@@ -753,7 +781,7 @@ static int ldb_probe(struct platform_device *pdev)
         struct ldb_chan *chan;
         enum crtc crtc;
         bool is_primary;
-        int ret;
+        int ret, timing_idx;
         ret = of_property_read_u32(child, "reg", &i);
         if (ret || i < 0 || i > 1 || i >= ldb->bus_mux_num) {
@@ -828,7 +856,10 @@ static int ldb_probe(struct platform_device *pdev)
             return -EINVAL;
         }
-        ret = of_get_videomode(child, &chan->vm, OF_USE_NATIVE_MODE);
+        timing_idx = get_ldb_timing(chan->chno);
+        ret = of_get_videomode(child, &chan->vm,
+            (timing_idx != ERR_NO_LVDS_TIMING) ?
+             timing_idx : OF_USE_NATIVE_MODE);
         if (ret)
             return -EINVAL;

[alejandrolozan1]

Thanks a lot Angelo!!