[PATCH v3] drm/i915: Fix wrong escape clock divisor init for GLK

Stanislav Lisovskiy
2019-07-12T08:19:38Z

According to Bspec clock divisor registers in GeminiLake
should be initialized by shifting 1(<<) to amount of correspondent
divisor. While i915 was writing all this time that value as is.

Surprisingly that it by accident worked, until we met some issues
with Microtech Etab.

v2: Added Fixes tag and cc
v3: Added stable to cc as well.

Signed-off-by: stanislav.lisovskiy@intel.com
Reviewed-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=108826
Fixes: bcc657004841 ("drm/i915/glk: Program txesc clock divider for GLK")
Cc: Deepak M <m.deepak@intel.com>
Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: stable@vger.kernel.org
---
drivers/gpu/drm/i915/display/vlv_dsi_pll.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/vlv_dsi_pll.c b/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
index 99cc3e2e9c2c..f016a776a39e 100644
--- a/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
+++ b/drivers/gpu/drm/i915/display/vlv_dsi_pll.c
@@ -396,8 +396,8 @@ static void glk_dsi_program_esc_clock(struct drm_device *dev,
else
txesc2_div = 10;

- I915_WRITE(MIPIO_TXESC_CLK_DIV1, txesc1_div & GLK_TX_ESC_CLK_DIV1_MASK);
- I915_WRITE(MIPIO_TXESC_CLK_DIV2, txesc2_div & GLK_TX_ESC_CLK_DIV2_MASK);
+ I915_WRITE(MIPIO_TXESC_CLK_DIV1, (1 << (txesc1_div - 1)) & GLK_TX_ESC_CLK_DIV1_MASK);
+ I915_WRITE(MIPIO_TXESC_CLK_DIV2, (1 << (txesc2_div - 1)) & GLK_TX_ESC_CLK_DIV2_MASK);
}

/* Program BXT Mipi clocks and dividers */
--
2.17.1