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path: root/drivers/video/ssd2828.c
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Diffstat (limited to 'drivers/video/ssd2828.c')
-rw-r--r--drivers/video/ssd2828.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/drivers/video/ssd2828.c b/drivers/video/ssd2828.c
index be68d38f81..8b09082254 100644
--- 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;
/*
@@ -374,6 +374,20 @@ 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.
*/
if (ssd2828_configure_video_interface(cfg, mode) != 0) {
@@ -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 */