[PATCH] OMAPDSS: HDMI: Cache EDID

[jaswinder.singh@linaro.org]

From: Jassi Brar <jaswinder.singh@linaro.org>

We can easily keep track of latest EDID from the display and hence avoid
expensive EDID re-reads over I2C.
This could also help some cheapo displays that provide EDID reliably only
immediately after asserting HPD and not later.
Even with good displays, there is something in OMAPDSS that apparantly
messes up DDC occasionally while EDID is being read, giving the
  "operation stopped when reading edid" error.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
---
 drivers/video/omap2/dss/hdmi.c            |    1 +
 drivers/video/omap2/dss/ti_hdmi.h         |    2 ++
 drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c |   23 ++++++++++++++++++++---
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/video/omap2/dss/hdmi.c b/drivers/video/omap2/dss/hdmi.c
index 900e621..0a8c825 100644
--- a/drivers/video/omap2/dss/hdmi.c
+++ b/drivers/video/omap2/dss/hdmi.c
@@ -764,6 +764,7 @@ static int __init omapdss_hdmihw_probe(struct platform_device *pdev)
 	hdmi.ip_data.core_av_offset = HDMI_CORE_AV;
 	hdmi.ip_data.pll_offset = HDMI_PLLCTRL;
 	hdmi.ip_data.phy_offset = HDMI_PHY;
+	hdmi.ip_data.edid_len = 0; /* Invalidate EDID Cache */
 	mutex_init(&hdmi.ip_data.lock);
 
 	hdmi_panel_init();
diff --git a/drivers/video/omap2/dss/ti_hdmi.h b/drivers/video/omap2/dss/ti_hdmi.h
index cc292b8..4735860 100644
--- a/drivers/video/omap2/dss/ti_hdmi.h
+++ b/drivers/video/omap2/dss/ti_hdmi.h
@@ -178,6 +178,8 @@ struct hdmi_ip_data {
 	/* ti_hdmi_4xxx_ip private data. These should be in a separate struct */
 	int hpd_gpio;
 	struct mutex lock;
+	u8 edid_cached[256];
+	unsigned edid_len;
 };
 int ti_hdmi_4xxx_phy_enable(struct hdmi_ip_data *ip_data);
 void ti_hdmi_4xxx_phy_disable(struct hdmi_ip_data *ip_data);
diff --git a/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c b/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
index 04acca9..2633ade 100644
--- a/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
+++ b/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
@@ -243,10 +243,13 @@ static int hdmi_check_hpd_state(struct hdmi_ip_data *ip_data)
 
 	hpd = gpio_get_value(ip_data->hpd_gpio);
 
-	if (hpd)
+	if (hpd) {
 		r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_TXON);
-	else
+	} else {
+		/* Invalidate EDID Cache */
+		ip_data->edid_len = 0;
 		r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_LDOON);
+	}
 
 	if (r) {
 		DSSERR("Failed to %s PHY TX power\n",
@@ -454,6 +457,11 @@ int ti_hdmi_4xxx_read_edid(struct hdmi_ip_data *ip_data,
 {
 	int r, l;
 
+	if (ip_data->edid_len) {
+		memcpy(edid, ip_data->edid_cached, ip_data->edid_len);
+		return ip_data->edid_len;
+	}
+
 	if (len < 128)
 		return -EINVAL;
 
@@ -474,12 +482,21 @@ int ti_hdmi_4xxx_read_edid(struct hdmi_ip_data *ip_data,
 		l += 128;
 	}
 
+	ip_data->edid_len = l;
+	memcpy(ip_data->edid_cached, edid, l);
+
 	return l;
 }
 
 bool ti_hdmi_4xxx_detect(struct hdmi_ip_data *ip_data)
 {
-	return gpio_get_value(ip_data->hpd_gpio);
+	if (gpio_get_value(ip_data->hpd_gpio))
+		return true;
+
+	/* Invalidate EDID Cache */
+	ip_data->edid_len = 0;
+
+	return false;
 }
 
 static void hdmi_core_init(struct hdmi_core_video_config *video_cfg,
-- 
1.7.4.1