drm/ast: fixed reading monitor EDID not stable issue

[ Upstream commit 300625620314194d9e6d4f6dda71f2dc9cf62d9f ]

v1: over-sample data to increase the stability with some specific monitors
v2: refine to avoid infinite loop
v3: remove un-necessary "volatile" declaration

[airlied: fix two checkpatch warnings]

Signed-off-by: Y.C. Chen <yc_chen@aspeedtech.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1542858988-1127-1-git-send-email-yc_chen@aspeedtech.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 21085f669e212d6d107d1313a288fa81e2e809d3..b19ba1792607c1e1325d81faf3d7973cfb0a6ea0 100644 (file)
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -968,9 +968,21 @@ static int get_clock(void *i2c_priv)
 {
        struct ast_i2c_chan *i2c = i2c_priv;
        struct ast_private *ast = i2c->dev->dev_private;
-       uint32_t val;
+       uint32_t val, val2, count, pass;
+
+       count = 0;
+       pass = 0;
+       val = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x10) >> 4) & 0x01;
+       do {
+               val2 = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x10) >> 4) & 0x01;
+               if (val == val2) {
+                       pass++;
+               } else {
+                       pass = 0;
+                       val = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x10) >> 4) & 0x01;
+               }
+       } while ((pass < 5) && (count++ < 0x10000));
 
-       val = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x10) >> 4;
        return val & 1 ? 1 : 0;
 }
 
@@ -978,9 +990,21 @@ static int get_data(void *i2c_priv)
 {
        struct ast_i2c_chan *i2c = i2c_priv;
        struct ast_private *ast = i2c->dev->dev_private;
-       uint32_t val;
+       uint32_t val, val2, count, pass;
+
+       count = 0;
+       pass = 0;
+       val = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x20) >> 5) & 0x01;
+       do {
+               val2 = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x20) >> 5) & 0x01;
+               if (val == val2) {
+                       pass++;
+               } else {
+                       pass = 0;
+                       val = (ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x20) >> 5) & 0x01;
+               }
+       } while ((pass < 5) && (count++ < 0x10000));
 
-       val = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x20) >> 5;
        return val & 1 ? 1 : 0;
 }
 
@@ -993,7 +1017,7 @@ static void set_clock(void *i2c_priv, int clock)
 
        for (i = 0; i < 0x10000; i++) {
                ujcrb7 = ((clock & 0x01) ? 0 : 1);
-               ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xfe, ujcrb7);
+               ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xf4, ujcrb7);
                jtemp = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x01);
                if (ujcrb7 == jtemp)
                        break;
@@ -1009,7 +1033,7 @@ static void set_data(void *i2c_priv, int data)
 
        for (i = 0; i < 0x10000; i++) {
                ujcrb7 = ((data & 0x01) ? 0 : 1) << 2;
-               ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xfb, ujcrb7);
+               ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xf1, ujcrb7);
                jtemp = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x04);
                if (ujcrb7 == jtemp)
                        break;