diff options
| author | Siarhei Siamashka <siarhei.siamashka@gmail.com> | 2015-01-19 05:23:35 +0200 |
|---|---|---|
| committer | Hans de Goede <hdegoede@redhat.com> | 2015-01-22 12:34:56 +0100 |
| commit | dddccd6913142e0ba63ce6e529c38651c2ab0197 (patch) | |
| tree | e1819e3251f887c0e2724be99b82f75512706ece /drivers/video/ssd2828.c | |
| parent | aaa6ac5eab8df95a3b9646194d90f49e79476258 (diff) | |
video: ssd2828: Allow using 'pclk' as the PLL clock source
Instead of using the internal 'tx_clk' clock source, it is also
possible to use the pixel clock signal from the parallel LCD
interface ('pclk') as the reference clock for PLL.
The 'tx_clk' clock speed may be different on different boards/devices
(the allowed range is 8MHz - 30MHz). Which is not very convenient,
especially considering the need to know the exact 'tx_clk' clock
speed. This clock speed may be difficult to identify without having
device schematics and/or accurate documentation/sources every time.
Using 'pclk' is free from all these problems.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Diffstat (limited to 'drivers/video/ssd2828.c')
| -rw-r--r-- | drivers/video/ssd2828.c | 20 |
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 */ |