drm/i915: Fix DSI panels with v1 MIPI sequences without a DEASSERT sequence v3

So far models of the Dell Venue 8 Pro, with a panel with MIPI panel
index = 3, one of which has been kindly provided to me by Jan Brummer,
where not working with the i915 driver, giving a black screen on the
first modeset.

The problem with at least these Dells is that their VBT defines a MIPI
ASSERT sequence, but not a DEASSERT sequence. Instead they DEASSERT the
reset in their INIT_OTP sequence, but the deassert must be done before
calling intel_dsi_device_ready(), so that is too late.

Simply doing the INIT_OTP sequence earlier is not enough to fix this,
because the INIT_OTP sequence also sends various MIPI packets to the
panel, which can only happen after calling intel_dsi_device_ready().

This commit fixes this by splitting the INIT_OTP sequence into everything
before the first DSI packet and everything else, including the first DSI
packet. The first part (everything before the first DSI packet) is then
used as deassert sequence.

Changed in v2:
-Split the init OTP sequence into a deassert reset and the actual init
 OTP sequence, instead of calling it earlier and then having the first
 mipi_exec_send_packet() call call intel_dsi_device_ready().

Changes in v3:
-Move the whole shebang to intel_bios.c

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82880
References: https://bugs.freedesktop.org/show_bug.cgi?id=101205
Cc: Jan-Michael Brummer <jan.brummer@tabos.org>
Reported-by: Jan-Michael Brummer <jan.brummer@tabos.org>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214082151.25015-3-hdegoede@redhat.com

drivers/gpu/drm/i915/i915_drv.h

@@ -1359,6 +1359,7 @@ struct intel_vbt_data {
 		u32 size;
 		u8 *data;
 		const u8 *sequence[MIPI_SEQ_MAX];
+		u8 *deassert_seq; /* Used by fixup_mipi_sequences() */
 	} dsi;
 
 	int crt_ddc_pin;

drivers/gpu/drm/i915/intel_bios.c

@@ -947,6 +947,86 @@ static int goto_next_sequence_v3(const u8 *data, int index, int total)
 	return 0;
 }
 
+/*
+ * Get len of pre-fixed deassert fragment from a v1 init OTP sequence,
+ * skip all delay + gpio operands and stop at the first DSI packet op.
+ */
+static int get_init_otp_deassert_fragment_len(struct drm_i915_private *dev_priv)
+{
+	const u8 *data = dev_priv->vbt.dsi.sequence[MIPI_SEQ_INIT_OTP];
+	int index, len;
+
+	if (WARN_ON(!data || dev_priv->vbt.dsi.seq_version != 1))
+		return 0;
+
+	/* index = 1 to skip sequence byte */
+	for (index = 1; data[index] != MIPI_SEQ_ELEM_END; index += len) {
+		switch (data[index]) {
+		case MIPI_SEQ_ELEM_SEND_PKT:
+			return index == 1 ? 0 : index;
+		case MIPI_SEQ_ELEM_DELAY:
+			len = 5; /* 1 byte for operand + uint32 */
+			break;
+		case MIPI_SEQ_ELEM_GPIO:
+			len = 3; /* 1 byte for op, 1 for gpio_nr, 1 for value */
+			break;
+		default:
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Some v1 VBT MIPI sequences do the deassert in the init OTP sequence.
+ * The deassert must be done before calling intel_dsi_device_ready, so for
+ * these devices we split the init OTP sequence into a deassert sequence and
+ * the actual init OTP part.
+ */
+static void fixup_mipi_sequences(struct drm_i915_private *dev_priv)
+{
+	u8 *init_otp;
+	int len;
+
+	/* Limit this to VLV for now. */
+	if (!IS_VALLEYVIEW(dev_priv))
+		return;
+
+	/* Limit this to v1 vid-mode sequences */
+	if (dev_priv->vbt.dsi.config->is_cmd_mode ||
+	    dev_priv->vbt.dsi.seq_version != 1)
+		return;
+
+	/* Only do this if there are otp and assert seqs and no deassert seq */
+	if (!dev_priv->vbt.dsi.sequence[MIPI_SEQ_INIT_OTP] ||
+	    !dev_priv->vbt.dsi.sequence[MIPI_SEQ_ASSERT_RESET] ||
+	    dev_priv->vbt.dsi.sequence[MIPI_SEQ_DEASSERT_RESET])
+		return;
+
+	/* The deassert-sequence ends at the first DSI packet */
+	len = get_init_otp_deassert_fragment_len(dev_priv);
+	if (!len)
+		return;
+
+	DRM_DEBUG_KMS("Using init OTP fragment to deassert reset\n");
+
+	/* Copy the fragment, update seq byte and terminate it */
+	init_otp = (u8 *)dev_priv->vbt.dsi.sequence[MIPI_SEQ_INIT_OTP];
+	dev_priv->vbt.dsi.deassert_seq = kmemdup(init_otp, len + 1, GFP_KERNEL);
+	if (!dev_priv->vbt.dsi.deassert_seq)
+		return;
+	dev_priv->vbt.dsi.deassert_seq[0] = MIPI_SEQ_DEASSERT_RESET;
+	dev_priv->vbt.dsi.deassert_seq[len] = MIPI_SEQ_ELEM_END;
+	/* Use the copy for deassert */
+	dev_priv->vbt.dsi.sequence[MIPI_SEQ_DEASSERT_RESET] =
+		dev_priv->vbt.dsi.deassert_seq;
+	/* Replace the last byte of the fragment with init OTP seq byte */
+	init_otp[len - 1] = MIPI_SEQ_INIT_OTP;
+	/* And make MIPI_MIPI_SEQ_INIT_OTP point to it */
+	dev_priv->vbt.dsi.sequence[MIPI_SEQ_INIT_OTP] = init_otp + len - 1;
+}
+
 static void
 parse_mipi_sequence(struct drm_i915_private *dev_priv,
 		    const struct bdb_header *bdb)
@@ -1016,6 +1096,8 @@ parse_mipi_sequence(struct drm_i915_private *dev_priv,
 	dev_priv->vbt.dsi.size = seq_size;
 	dev_priv->vbt.dsi.seq_version = sequence->version;
 
+	fixup_mipi_sequences(dev_priv);
+
 	DRM_DEBUG_DRIVER("MIPI related VBT parsing complete\n");
 	return;
 
@@ -1629,6 +1711,8 @@ void intel_bios_cleanup(struct drm_i915_private *dev_priv)
 	dev_priv->vbt.dsi.pps = NULL;
 	kfree(dev_priv->vbt.dsi.config);
 	dev_priv->vbt.dsi.config = NULL;
+	kfree(dev_priv->vbt.dsi.deassert_seq);
+	dev_priv->vbt.dsi.deassert_seq = NULL;
 }
 
 /**