OMAPDSS: HDMI: PHY burnout fix

A hardware bug in the OMAP4 HDMI PHY causes physical damage to the board
if the HDMI PHY is kept powered on when the cable is not connected.

This patch solves the problem by adding hot-plug-detection into the HDMI
IP driver. This is not a real HPD support in the sense that nobody else
than the IP driver gets to know about the HPD events, but is only meant
to fix the HW bug.

The strategy is simple: If the display device is turned off by the user,
the PHY power is set to OFF. When the display device is turned on by the
user, the PHY power is set either to LDOON or TXON, depending on whether
the HDMI cable is connected.

The reason to avoid PHY OFF when the display device is on, but the cable
is disconnected, is that when the PHY is turned OFF, the HDMI IP is not
"ticking" and thus the DISPC does not receive pixel clock from the HDMI
IP. This would, for example, prevent any VSYNCs from happening, and
would thus affect the users of omapdss. By using LDOON when the cable is
disconnected we'll avoid the HW bug, but keep the HDMI working as usual
from the user's point of view.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

3 files changed, 71 insertions, 4 deletions

diff --git a/drivers/video/omap2/dss/hdmi.c b/drivers/video/omap2/dss/hdmi.c
index c39f9c3a92cf..d7aa3b056529 100644
--- a/drivers/video/omap2/dss/hdmi.c
+++ b/drivers/video/omap2/dss/hdmi.c
@@ -497,6 +497,7 @@ bool omapdss_hdmi_detect(void)
 
 int omapdss_hdmi_display_enable(struct omap_dss_device *dssdev)
 {
+        struct omap_dss_hdmi_data *priv = dssdev->data;
         int r = 0;
 
         DSSDBG("ENTER hdmi_display_enable\n");
@@ -509,6 +510,8 @@ int omapdss_hdmi_display_enable(struct omap_dss_device *dssdev)
                 goto err0;
         }
 
+        hdmi.ip_data.hpd_gpio = priv->hpd_gpio;
+
         r = omap_dss_start_device(dssdev);
         if (r) {
                 DSSERR("failed to start device\n");
diff --git a/drivers/video/omap2/dss/ti_hdmi.h b/drivers/video/omap2/dss/ti_hdmi.h
index 7503f7f619a7..50dadba5070a 100644
--- a/drivers/video/omap2/dss/ti_hdmi.h
+++ b/drivers/video/omap2/dss/ti_hdmi.h
@@ -126,6 +126,10 @@ struct hdmi_ip_data {
         const struct ti_hdmi_ip_ops *ops;
         struct hdmi_config cfg;
         struct hdmi_pll_info pll_data;
+
+        /* ti_hdmi_4xxx_ip private data. These should be in a separate struct */
+        int hpd_gpio;
+        bool phy_tx_enabled;
 };
 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 9af81f18f163..2d72334ca3da 100644
--- a/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
+++ b/drivers/video/omap2/dss/ti_hdmi_4xxx_ip.c
@@ -28,6 +28,7 @@
 #include <linux/delay.h>
 #include <linux/string.h>
 #include <linux/seq_file.h>
+#include <linux/gpio.h>
 
 #include "ti_hdmi_4xxx_ip.h"
 #include "dss.h"
@@ -223,6 +224,49 @@ void ti_hdmi_4xxx_pll_disable(struct hdmi_ip_data *ip_data)
         hdmi_set_pll_pwr(ip_data, HDMI_PLLPWRCMD_ALLOFF);
 }
 
+static int hdmi_check_hpd_state(struct hdmi_ip_data *ip_data)
+{
+        unsigned long flags;
+        bool hpd;
+        int r;
+        /* this should be in ti_hdmi_4xxx_ip private data */
+        static DEFINE_SPINLOCK(phy_tx_lock);
+
+        spin_lock_irqsave(&phy_tx_lock, flags);
+
+        hpd = gpio_get_value(ip_data->hpd_gpio);
+
+        if (hpd == ip_data->phy_tx_enabled) {
+                spin_unlock_irqrestore(&phy_tx_lock, flags);
+                return 0;
+        }
+
+        if (hpd)
+                r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_TXON);
+        else
+                r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_LDOON);
+
+        if (r) {
+                DSSERR("Failed to %s PHY TX power\n",
+                                hpd ? "enable" : "disable");
+                goto err;
+        }
+
+        ip_data->phy_tx_enabled = hpd;
+err:
+        spin_unlock_irqrestore(&phy_tx_lock, flags);
+        return r;
+}
+
+static irqreturn_t hpd_irq_handler(int irq, void *data)
+{
+        struct hdmi_ip_data *ip_data = data;
+
+        hdmi_check_hpd_state(ip_data);
+
+        return IRQ_HANDLED;
+}
+
 int ti_hdmi_4xxx_phy_enable(struct hdmi_ip_data *ip_data)
 {
         u16 r = 0;
@@ -232,10 +276,6 @@ int ti_hdmi_4xxx_phy_enable(struct hdmi_ip_data *ip_data)
         if (r)
                 return r;
 
-        r = hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_TXON);
-        if (r)
-                return r;
-
         /*
          * Read address 0 in order to get the SCP reset done completed
          * Dummy access performed to make sure reset is done
@@ -257,12 +297,32 @@ int ti_hdmi_4xxx_phy_enable(struct hdmi_ip_data *ip_data)
         /* Write to phy address 3 to change the polarity control */
         REG_FLD_MOD(phy_base, HDMI_TXPHY_PAD_CFG_CTRL, 0x1, 27, 27);
 
+        r = request_threaded_irq(gpio_to_irq(ip_data->hpd_gpio),
+                        NULL, hpd_irq_handler,
+                        IRQF_DISABLED | IRQF_TRIGGER_RISING |
+                        IRQF_TRIGGER_FALLING, "hpd", ip_data);
+        if (r) {
+                DSSERR("HPD IRQ request failed\n");
+                hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_OFF);
+                return r;
+        }
+
+        r = hdmi_check_hpd_state(ip_data);
+        if (r) {
+                free_irq(gpio_to_irq(ip_data->hpd_gpio), ip_data);
+                hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_OFF);
+                return r;
+        }
+
         return 0;
 }
 
 void ti_hdmi_4xxx_phy_disable(struct hdmi_ip_data *ip_data)
 {
+        free_irq(gpio_to_irq(ip_data->hpd_gpio), ip_data);
+
         hdmi_set_phy_pwr(ip_data, HDMI_PHYPWRCMD_OFF);
+        ip_data->phy_tx_enabled = false;
 }
 
 static int hdmi_core_ddc_init(struct hdmi_ip_data *ip_data)