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Subject[PATCH v16 11/40] drm/tegra: dc: Support OPP and SoC core voltage scaling
Date
Add OPP and SoC core voltage scaling support to the display controller
driver. This is required for enabling system-wide DVFS on pre-Tegra186
SoCs.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30
Tested-by: Paul Fertser <fercerpav@gmail.com> # PAZ00 T20
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20 and TK1 T124
Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/gpu/drm/tegra/dc.c | 79 ++++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/tegra/dc.h | 2 +
2 files changed, 81 insertions(+)

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index a457ee954a49..eb70eee8992a 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -11,9 +11,12 @@
#include <linux/interconnect.h>
#include <linux/module.h>
#include <linux/of_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>

+#include <soc/tegra/common.h>
#include <soc/tegra/pmc.h>

#include <drm/drm_atomic.h>
@@ -1834,6 +1837,52 @@ int tegra_dc_state_setup_clock(struct tegra_dc *dc,
return 0;
}

+static void tegra_dc_update_voltage_state(struct tegra_dc *dc,
+ struct tegra_dc_state *state)
+{
+ unsigned long rate, pstate;
+ struct dev_pm_opp *opp;
+ int err;
+
+ if (!dc->has_opp_table)
+ return;
+
+ /* calculate actual pixel clock rate which depends on internal divider */
+ rate = DIV_ROUND_UP(clk_get_rate(dc->clk) * 2, state->div + 2);
+
+ /* find suitable OPP for the rate */
+ opp = dev_pm_opp_find_freq_ceil(dc->dev, &rate);
+
+ /*
+ * Very high resolution modes may results in a clock rate that is
+ * above the characterized maximum. In this case it's okay to fall
+ * back to the characterized maximum.
+ */
+ if (opp == ERR_PTR(-ERANGE))
+ opp = dev_pm_opp_find_freq_floor(dc->dev, &rate);
+
+ if (IS_ERR(opp)) {
+ dev_err(dc->dev, "failed to find OPP for %luHz: %pe\n",
+ rate, opp);
+ return;
+ }
+
+ pstate = dev_pm_opp_get_required_pstate(opp, 0);
+ dev_pm_opp_put(opp);
+
+ /*
+ * The minimum core voltage depends on the pixel clock rate (which
+ * depends on internal clock divider of the CRTC) and not on the
+ * rate of the display controller clock. This is why we're not using
+ * dev_pm_opp_set_rate() API and instead controlling the power domain
+ * directly.
+ */
+ err = dev_pm_genpd_set_performance_state(dc->dev, pstate);
+ if (err)
+ dev_err(dc->dev, "failed to set power domain state to %lu: %d\n",
+ pstate, err);
+}
+
static void tegra_dc_set_clock_rate(struct tegra_dc *dc,
struct tegra_dc_state *state)
{
@@ -1867,6 +1916,8 @@ static void tegra_dc_set_clock_rate(struct tegra_dc *dc,
DRM_DEBUG_KMS("rate: %lu, div: %u\n", clk_get_rate(dc->clk),
state->div);
DRM_DEBUG_KMS("pclk: %lu\n", state->pclk);
+
+ tegra_dc_update_voltage_state(dc, state);
}

static void tegra_dc_stop(struct tegra_dc *dc)
@@ -2057,6 +2108,13 @@ static void tegra_crtc_atomic_disable(struct drm_crtc *crtc,
err = host1x_client_suspend(&dc->client);
if (err < 0)
dev_err(dc->dev, "failed to suspend: %d\n", err);
+
+ if (dc->has_opp_table) {
+ err = dev_pm_genpd_set_performance_state(dc->dev, 0);
+ if (err)
+ dev_err(dc->dev,
+ "failed to clear power domain state: %d\n", err);
+ }
}

static void tegra_crtc_atomic_enable(struct drm_crtc *crtc,
@@ -3058,6 +3116,23 @@ static int tegra_dc_couple(struct tegra_dc *dc)
return 0;
}

+static int tegra_dc_init_opp_table(struct tegra_dc *dc)
+{
+ struct tegra_core_opp_params opp_params = {};
+ int err;
+
+ err = devm_tegra_core_dev_init_opp_table(dc->dev, &opp_params);
+ if (err && err != -ENODEV)
+ return err;
+
+ if (err)
+ dc->has_opp_table = false;
+ else
+ dc->has_opp_table = true;
+
+ return 0;
+}
+
static int tegra_dc_probe(struct platform_device *pdev)
{
u64 dma_mask = dma_get_mask(pdev->dev.parent);
@@ -3123,6 +3198,10 @@ static int tegra_dc_probe(struct platform_device *pdev)
tegra_powergate_power_off(dc->powergate);
}

+ err = tegra_dc_init_opp_table(dc);
+ if (err < 0)
+ return err;
+
dc->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(dc->regs))
return PTR_ERR(dc->regs);
diff --git a/drivers/gpu/drm/tegra/dc.h b/drivers/gpu/drm/tegra/dc.h
index c9c4c45c0518..3f91a10ea6c7 100644
--- a/drivers/gpu/drm/tegra/dc.h
+++ b/drivers/gpu/drm/tegra/dc.h
@@ -101,6 +101,8 @@ struct tegra_dc {
struct drm_info_list *debugfs_files;

const struct tegra_dc_soc_info *soc;
+
+ bool has_opp_table;
};

static inline struct tegra_dc *
--
2.33.1
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