video: ssd2828: Allow using 'pclk' as the PLL clock source

[karo-tx-uboot.git] / drivers / video / ssd2828.c

diff --git a/drivers/video/ssd2828.c b/drivers/video/ssd2828.c
index be68d38f8109680978bf6f9d2c634fa7db5a28ad..8b090822549c1febd46b1886a217650f15fe261b 100644 (file)
--- a/drivers/video/ssd2828.c
+++ b/drivers/video/ssd2828.c
@@ -340,7 +340,7 @@ static int ssd2828_configure_video_interface(const struct ssd2828_config *cfg,
 int ssd2828_init(const struct ssd2828_config *cfg,
                 const struct ctfb_res_modes *mode)
 {
-       u32 lp_div, pll_freq_kbps, pll_config;
+       u32 lp_div, pll_freq_kbps, reference_freq_khz, pll_config;
        /* The LP clock speed is limited by 10MHz */
        const u32 mipi_dsi_low_power_clk_khz = 10000;
        /*
@@ -373,6 +373,20 @@ int ssd2828_init(const struct ssd2828_config *cfg,
                }
        }
 
+       /*
+        * Pick the reference clock for PLL. If we know the exact 'tx_clk'
+        * clock speed, then everything is good. If not, then we can fallback
+        * to 'pclk' (pixel clock from the parallel LCD interface). In the
+        * case of using this fallback, it is necessary to have parallel LCD
+        * already initialized and running at this point.
+        */
+       reference_freq_khz = cfg->ssd2828_tx_clk_khz;
+       if (reference_freq_khz  == 0) {
+               reference_freq_khz = mode->pixclock_khz;
+               /* Use 'pclk' as the reference clock for PLL */
+               cfgr_reg |= SSD2828_CFGR_CSS;
+       }
+
        /*
         * Setup the parallel LCD timings in the appropriate registers.
         */
@@ -390,10 +404,10 @@ int ssd2828_init(const struct ssd2828_config *cfg,
        /* PLL Configuration Register */
        pll_config = construct_pll_config(
                                cfg->mipi_dsi_bitrate_per_data_lane_mbps * 1000,
-                               cfg->ssd2828_tx_clk_khz);
+                               reference_freq_khz);
        write_hw_register(cfg, SSD2828_PLCR, pll_config);
 
-       pll_freq_kbps = decode_pll_config(pll_config, cfg->ssd2828_tx_clk_khz);
+       pll_freq_kbps = decode_pll_config(pll_config, reference_freq_khz);
        lp_div = DIV_ROUND_UP(pll_freq_kbps, mipi_dsi_low_power_clk_khz * 8);
 
        /* VC Control Register */