drm/i2c: tda998x: check more I/O errors

This patch adds more error checking inn I2C I/O functions.
In case of I/O error, this permits to avoid writing in bad controller
pages, a bad chipset detection or looping when getting the EDID.

Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 43 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 7df73baf3f9b..9bd336cdb734 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -363,7 +363,7 @@ fail:
         return 0;
 }
 
-static void
+static int
 set_page(struct tda998x_priv *priv, uint16_t reg)
 {
         if (REG2PAGE(reg) != priv->current_page) {
@@ -372,11 +372,14 @@ set_page(struct tda998x_priv *priv, uint16_t reg)
                                 REG_CURPAGE, REG2PAGE(reg)
                 };
                 int ret = i2c_master_send(client, buf, sizeof(buf));
-                if (ret < 0)
+                if (ret < 0) {
                         dev_err(&client->dev, "Error %d writing to REG_CURPAGE\n", ret);
+                        return ret;
+                }
 
                 priv->current_page = REG2PAGE(reg);
         }
+        return 0;
 }
 
 static int
@@ -386,7 +389,9 @@ reg_read_range(struct tda998x_priv *priv, uint16_t reg, char *buf, int cnt)
         uint8_t addr = REG2ADDR(reg);
         int ret;
 
-        set_page(priv, reg);
+        ret = set_page(priv, reg);
+        if (ret < 0)
+                return ret;
 
         ret = i2c_master_send(client, &addr, sizeof(addr));
         if (ret < 0)
@@ -413,18 +418,24 @@ reg_write_range(struct tda998x_priv *priv, uint16_t reg, uint8_t *p, int cnt)
         buf[0] = REG2ADDR(reg);
         memcpy(&buf[1], p, cnt);
 
-        set_page(priv, reg);
+        ret = set_page(priv, reg);
+        if (ret < 0)
+                return;
 
         ret = i2c_master_send(client, buf, cnt + 1);
         if (ret < 0)
                 dev_err(&client->dev, "Error %d writing to 0x%x\n", ret, reg);
 }
 
-static uint8_t
+static int
 reg_read(struct tda998x_priv *priv, uint16_t reg)
 {
         uint8_t val = 0;
-        reg_read_range(priv, reg, &val, sizeof(val));
+        int ret;
+
+        ret = reg_read_range(priv, reg, &val, sizeof(val));
+        if (ret < 0)
+                return ret;
         return val;
 }
 
@@ -435,7 +446,9 @@ reg_write(struct tda998x_priv *priv, uint16_t reg, uint8_t val)
         uint8_t buf[] = {REG2ADDR(reg), val};
         int ret;
 
-        set_page(priv, reg);
+        ret = set_page(priv, reg);
+        if (ret < 0)
+                return;
 
         ret = i2c_master_send(client, buf, ARRAY_SIZE(buf));
         if (ret < 0)
@@ -449,7 +462,9 @@ reg_write16(struct tda998x_priv *priv, uint16_t reg, uint16_t val)
         uint8_t buf[] = {REG2ADDR(reg), val >> 8, val};
         int ret;
 
-        set_page(priv, reg);
+        ret = set_page(priv, reg);
+        if (ret < 0)
+                return;
 
         ret = i2c_master_send(client, buf, ARRAY_SIZE(buf));
         if (ret < 0)
@@ -459,13 +474,21 @@ reg_write16(struct tda998x_priv *priv, uint16_t reg, uint16_t val)
 static void
 reg_set(struct tda998x_priv *priv, uint16_t reg, uint8_t val)
 {
-        reg_write(priv, reg, reg_read(priv, reg) | val);
+        int old_val;
+
+        old_val = reg_read(priv, reg);
+        if (old_val >= 0)
+                reg_write(priv, reg, old_val | val);
 }
 
 static void
 reg_clear(struct tda998x_priv *priv, uint16_t reg, uint8_t val)
 {
-        reg_write(priv, reg, reg_read(priv, reg) & ~val);
+        int old_val;
+
+        old_val = reg_read(priv, reg);
+        if (old_val >= 0)
+                reg_write(priv, reg, old_val & ~val);
 }
 
 static void
@@ -978,8 +1001,10 @@ read_edid_block(struct drm_encoder *encoder, uint8_t *buf, int blk)
 
         /* wait for block read to complete: */
         for (i = 100; i > 0; i--) {
-                uint8_t val = reg_read(priv, REG_INT_FLAGS_2);
-                if (val & INT_FLAGS_2_EDID_BLK_RD)
+                ret = reg_read(priv, REG_INT_FLAGS_2);
+                if (ret < 0)
+                        return ret;
+                if (ret & INT_FLAGS_2_EDID_BLK_RD)
                         break;
                 msleep(1);
         }
@@ -1144,6 +1169,7 @@ tda998x_encoder_init(struct i2c_client *client,
                     struct drm_encoder_slave *encoder_slave)
 {
         struct tda998x_priv *priv;
+        int ret;
 
         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
         if (!priv)
@@ -1172,8 +1198,11 @@ tda998x_encoder_init(struct i2c_client *client,
         tda998x_reset(priv);
 
         /* read version: */
-        priv->rev = reg_read(priv, REG_VERSION_LSB) |
-                        reg_read(priv, REG_VERSION_MSB) << 8;
+        ret = reg_read(priv, REG_VERSION_LSB) |
+                (reg_read(priv, REG_VERSION_MSB) << 8);
+        if (ret < 0)
+                goto fail;
+        priv->rev = ret;
 
         /* mask off feature bits: */
         priv->rev &= ~0x30; /* not-hdcp and not-scalar bit */