diff options
| author | Michael Tretter <m.tretter@pengutronix.de> | 2023-10-06 18:07:05 +0300 |
|---|---|---|
| committer | Neil Armstrong <neil.armstrong@linaro.org> | 2023-10-09 12:06:22 +0300 |
| commit | 846307185f0ffbbe6b34d53b97c31c0fc392cff0 (patch) | |
| tree | b0b845e1a96e837f1f1e93031388590bf0b85f93 /drivers/gpu | |
| parent | eb26c6ab2a11e6c595ee88ce30c7de9578d957aa (diff) | |
| download | linux-846307185f0ffbbe6b34d53b97c31c0fc392cff0.tar.xz | |
drm/bridge: samsung-dsim: update PLL reference clock
The PLL requires a clock frequency in a certain platform-dependent range
after the pre-divider. The reference clock for the PLL may change due to
changes to it's parent clock. Thus, the frequency may be out of range or
unsuited for generating the high speed clock for MIPI DSI.
Try to keep the pre-devider small, and set the reference clock close to
the upper limit before recalculating the PLL configuration. Use a
divider with a power of two for the reference clock as this seems to
work best in my tests.
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de> # Kontron BL i.MX8MM + Waveshare 10.1inch HDMI LCD (E)
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20230818-samsung-dsim-v2-3-846603df0e0a@pengutronix.de
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230818-samsung-dsim-v2-3-846603df0e0a@pengutronix.de
Diffstat (limited to 'drivers/gpu')
| -rw-r--r-- | drivers/gpu/drm/bridge/samsung-dsim.c | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c index 71fc0a8766ff..60d5ab2e0989 100644 --- a/drivers/gpu/drm/bridge/samsung-dsim.c +++ b/drivers/gpu/drm/bridge/samsung-dsim.c @@ -410,6 +410,8 @@ static const struct samsung_dsim_driver_data exynos3_dsi_driver_data = { .num_bits_resol = 11, .pll_p_offset = 13, .reg_values = reg_values, + .pll_fin_min = 6, + .pll_fin_max = 12, .m_min = 41, .m_max = 125, .min_freq = 500, @@ -427,6 +429,8 @@ static const struct samsung_dsim_driver_data exynos4_dsi_driver_data = { .num_bits_resol = 11, .pll_p_offset = 13, .reg_values = reg_values, + .pll_fin_min = 6, + .pll_fin_max = 12, .m_min = 41, .m_max = 125, .min_freq = 500, @@ -442,6 +446,8 @@ static const struct samsung_dsim_driver_data exynos5_dsi_driver_data = { .num_bits_resol = 11, .pll_p_offset = 13, .reg_values = reg_values, + .pll_fin_min = 6, + .pll_fin_max = 12, .m_min = 41, .m_max = 125, .min_freq = 500, @@ -457,6 +463,8 @@ static const struct samsung_dsim_driver_data exynos5433_dsi_driver_data = { .num_bits_resol = 12, .pll_p_offset = 13, .reg_values = exynos5433_reg_values, + .pll_fin_min = 6, + .pll_fin_max = 12, .m_min = 41, .m_max = 125, .min_freq = 500, @@ -472,6 +480,8 @@ static const struct samsung_dsim_driver_data exynos5422_dsi_driver_data = { .num_bits_resol = 12, .pll_p_offset = 13, .reg_values = exynos5422_reg_values, + .pll_fin_min = 6, + .pll_fin_max = 12, .m_min = 41, .m_max = 125, .min_freq = 500, @@ -491,6 +501,8 @@ static const struct samsung_dsim_driver_data imx8mm_dsi_driver_data = { */ .pll_p_offset = 14, .reg_values = imx8mm_dsim_reg_values, + .pll_fin_min = 2, + .pll_fin_max = 30, .m_min = 64, .m_max = 1023, .min_freq = 1050, @@ -614,10 +626,21 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi, u16 m; u32 reg; - if (dsi->pll_clk) + if (dsi->pll_clk) { + /* + * Ensure that the reference clock is generated with a power of + * two divider from its parent, but close to the PLLs upper + * limit. + */ + fin = clk_get_rate(clk_get_parent(dsi->pll_clk)); + while (fin > driver_data->pll_fin_max * MHZ) + fin /= 2; + clk_set_rate(dsi->pll_clk, fin); + fin = clk_get_rate(dsi->pll_clk); - else + } else { fin = dsi->pll_clk_rate; + } dev_dbg(dsi->dev, "PLL ref clock freq %lu\n", fin); fout = samsung_dsim_pll_find_pms(dsi, fin, freq, &p, &m, &s); |