Re: [PATCH v2 05/13] drm/bridge: lt9611: fix clock calculation

[Neil Armstrong]

On 08/01/2023 17:56, Dmitry Baryshkov wrote:

Instead of having several fixed values for the pcr register, calculate
it before programming. This allows the bridge to support most of the
display modes.

Fixes: 23278bf54afe ("drm/bridge: Introduce LT9611 DSI to HDMI bridge")
Signed-off-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>
---
  drivers/gpu/drm/bridge/lontium-lt9611.c | 32 +++++++++++--------------
  1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c 
b/drivers/gpu/drm/bridge/lontium-lt9611.c
index f377052a45a4..e2799a0df8f8 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -192,8 +192,9 @@ static void lt9611_mipi_video_setup(struct lt9611 *lt9611,
        regmap_write(lt9611->regmap, 0x831b, (u8)(hsync_porch % 256));
  }

-static void lt9611_pcr_setup(struct lt9611 *lt9611, const struct drm_display_mode *mode)

+static void lt9611_pcr_setup(struct lt9611 *lt9611, const struct 
drm_display_mode *mode, unsigned int postdiv)
  {
+       unsigned int pcr_m = mode->clock * 5 * postdiv / 27000;
        const struct reg_sequence reg_cfg[] = {
                { 0x830b, 0x01 },
                { 0x830c, 0x10 },
@@ -236,24 +237,14 @@ static void lt9611_pcr_setup(struct lt9611 *lt9611, const 
struct drm_display_mod
        else
                regmap_multi_reg_write(lt9611->regmap, reg_cfg, 
ARRAY_SIZE(reg_cfg));

- switch (mode->hdisplay) {

-       case 640:
-               regmap_write(lt9611->regmap, 0x8326, 0x14);
-               break;
-       case 1920:
-               regmap_write(lt9611->regmap, 0x8326, 0x37);
-               break;
-       case 3840:
-               regmap_write(lt9611->regmap, 0x8326, 0x37);
-               break;
-       }
+       regmap_write(lt9611->regmap, 0x8326, pcr_m);

/* pcr rst */

        regmap_write(lt9611->regmap, 0x8011, 0x5a);
        regmap_write(lt9611->regmap, 0x8011, 0xfa);
  }

-static int lt9611_pll_setup(struct lt9611 *lt9611, const struct drm_display_mode *mode)

+static int lt9611_pll_setup(struct lt9611 *lt9611, const struct 
drm_display_mode *mode, unsigned int *postdiv)
  {
        unsigned int pclk = mode->clock;
        const struct reg_sequence reg_cfg[] = {
@@ -271,12 +262,16 @@ static int lt9611_pll_setup(struct lt9611 *lt9611, const 
struct drm_display_mode

regmap_multi_reg_write(lt9611->regmap, reg_cfg, ARRAY_SIZE(reg_cfg)); - if (pclk > 150000)

+       if (pclk > 150000) {
                regmap_write(lt9611->regmap, 0x812d, 0x88);
-       else if (pclk > 70000)
+               *postdiv = 1;
+       } else if (pclk > 70000) {
                regmap_write(lt9611->regmap, 0x812d, 0x99);
-       else
+               *postdiv = 2;
+       } else {
                regmap_write(lt9611->regmap, 0x812d, 0xaa);
+               *postdiv = 4;
+       }

/*

         * first divide pclk by 2 first
@@ -895,14 +890,15 @@ static void lt9611_bridge_mode_set(struct drm_bridge 
*bridge,
  {
        struct lt9611 *lt9611 = bridge_to_lt9611(bridge);
        struct hdmi_avi_infoframe avi_frame;
+       unsigned int postdiv;
        int ret;

lt9611_bridge_pre_enable(bridge); lt9611_mipi_input_digital(lt9611, mode);

-       lt9611_pll_setup(lt9611, mode);
+       lt9611_pll_setup(lt9611, mode, &postdiv);
        lt9611_mipi_video_setup(lt9611, mode);
-       lt9611_pcr_setup(lt9611, mode);
+       lt9611_pcr_setup(lt9611, mode, postdiv);

ret = drm_hdmi_avi_infoframe_from_display_mode(&avi_frame,

                                                       &lt9611->connector,

Reviewed-by: Neil Armstrong <neil.armstr...@linaro.org>