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    Subject[PATCH AUTOSEL 4.14 54/69] drm/ast: fixed reading monitor EDID not stable issue
    Date
    From: "Y.C. Chen" <yc_chen@aspeedtech.com>

    [ 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>
    ---
    drivers/gpu/drm/ast/ast_mode.c | 36 ++++++++++++++++++++++++++++------
    1 file changed, 30 insertions(+), 6 deletions(-)

    diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
    index fae1176b2472..343867b182dd 100644
    --- a/drivers/gpu/drm/ast/ast_mode.c
    +++ b/drivers/gpu/drm/ast/ast_mode.c
    @@ -973,9 +973,21 @@ 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;
    }

    @@ -983,9 +995,21 @@ 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;
    }

    @@ -998,7 +1022,7 @@ 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;
    @@ -1014,7 +1038,7 @@ 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;
    --
    2.17.1
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