diff options
| -rw-r--r-- | drivers/gpu/drm/tegra/rgb.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c index 78e3cb1529d0..be1b38936dbe 100644 --- a/drivers/gpu/drm/tegra/rgb.c +++ b/drivers/gpu/drm/tegra/rgb.c @@ -235,6 +235,47 @@ static void tegra_rgb_encoder_disable(struct drm_encoder *encoder) drm_panel_unprepare(output->panel); } +static int +tegra_rgb_encoder_atomic_check(struct drm_encoder *encoder, + struct drm_crtc_state *crtc_state, + struct drm_connector_state *conn_state) +{ + struct tegra_output *output = encoder_to_output(encoder); + struct tegra_dc *dc = to_tegra_dc(conn_state->crtc); + unsigned long pclk = crtc_state->mode.clock * 1000; + struct tegra_rgb *rgb = to_rgb(output); + unsigned int div; + int err; + + /* + * We may not want to change the frequency of the parent clock, since + * it may be a parent for other peripherals. This is due to the fact + * that on Tegra20 there's only a single clock dedicated to display + * (pll_d_out0), whereas later generations have a second one that can + * be used to independently drive a second output (pll_d2_out0). + * + * As a way to support multiple outputs on Tegra20 as well, pll_p is + * typically used as the parent clock for the display controllers. + * But this comes at a cost: pll_p is the parent of several other + * peripherals, so its frequency shouldn't change out of the blue. + * + * The best we can do at this point is to use the shift clock divider + * and hope that the desired frequency can be matched (or at least + * matched sufficiently close that the panel will still work). + */ + div = ((clk_get_rate(rgb->clk) * 2) / pclk) - 2; + pclk = 0; + + err = tegra_dc_state_setup_clock(dc, crtc_state, rgb->clk_parent, + pclk, div); + if (err < 0) { + dev_err(output->dev, "failed to setup CRTC state: %d\n", err); + return err; + } + + return err; +} + static const struct drm_encoder_helper_funcs tegra_rgb_encoder_helper_funcs = { .dpms = tegra_rgb_encoder_dpms, .mode_fixup = tegra_rgb_encoder_mode_fixup, @@ -242,6 +283,7 @@ static const struct drm_encoder_helper_funcs tegra_rgb_encoder_helper_funcs = { .commit = tegra_rgb_encoder_commit, .mode_set = tegra_rgb_encoder_mode_set, .disable = tegra_rgb_encoder_disable, + .atomic_check = tegra_rgb_encoder_atomic_check, }; int tegra_dc_rgb_probe(struct tegra_dc *dc) |