ALSA: hda - fail ELD reading early
Wu Fengguang [Tue, 22 Nov 2011 08:46:23 +0000 (16:46 +0800)]
With the ELD repoll mechanism, we can (and should) fail the ELD reading
immediately when find something obviously wrong and let the caller retry
after some delay.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_eld.c

index 7ae7578..c1da422 100644 (file)
@@ -347,18 +347,28 @@ int snd_hdmi_get_eld(struct hdmi_eld *eld,
 
        for (i = 0; i < size; i++) {
                unsigned int val = hdmi_get_eld_data(codec, nid, i);
+               /*
+                * Graphics driver might be writing to ELD buffer right now.
+                * Just abort. The caller will repoll after a while.
+                */
                if (!(val & AC_ELDD_ELD_VALID)) {
-                       if (!i) {
-                               snd_printd(KERN_INFO
-                                          "HDMI: invalid ELD data\n");
-                               ret = -EINVAL;
-                               goto error;
-                       }
                        snd_printd(KERN_INFO
                                  "HDMI: invalid ELD data byte %d\n", i);
-                       val = 0;
-               } else
-                       val &= AC_ELDD_ELD_DATA;
+                       ret = -EINVAL;
+                       goto error;
+               }
+               val &= AC_ELDD_ELD_DATA;
+               /*
+                * The first byte cannot be zero. This can happen on some DVI
+                * connections. Some Intel chips may also need some 250ms delay
+                * to return non-zero ELD data, even when the graphics driver
+                * correctly writes ELD content before setting ELD_valid bit.
+                */
+               if (!val && !i) {
+                       snd_printdd(KERN_INFO "HDMI: 0 ELD data\n");
+                       ret = -EINVAL;
+                       goto error;
+               }
                buf[i] = val;
        }