[PATCH v1 11/30] drm/tegra: dc: Support OPP and SoC core voltage scaling

Dmitry Osipenko
2020-11-04T23:49:02Z

Add OPP and SoC core voltage scaling support to the display controller
driver. This is required for enabling system-wide DVFS on older Tegra
SoCs.

Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/gpu/drm/tegra/Kconfig | 1 +
drivers/gpu/drm/tegra/dc.c | 138 +++++++++++++++++++++++++++++++++-
drivers/gpu/drm/tegra/dc.h | 5 ++
3 files changed, 143 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tegra/Kconfig b/drivers/gpu/drm/tegra/Kconfig
index 1650a448eabd..9eec4c3fbd3b 100644
--- a/drivers/gpu/drm/tegra/Kconfig
+++ b/drivers/gpu/drm/tegra/Kconfig
@@ -12,6 +12,7 @@ config DRM_TEGRA
select INTERCONNECT
select IOMMU_IOVA
select CEC_CORE if CEC_NOTIFIER
+ select PM_OPP
help
Choose this option if you have an NVIDIA Tegra SoC.

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index fd7c8828652d..babcb66a335b 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -11,9 +11,13 @@
#include <linux/interconnect.h>
#include <linux/module.h>
#include <linux/of_device.h>
+#include <linux/pm_opp.h>
#include <linux/pm_runtime.h>
+#include <linux/regulator/consumer.h>
#include <linux/reset.h>

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

#include <drm/drm_atomic.h>
@@ -1699,6 +1703,55 @@ 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)
+{
+ struct dev_pm_opp *opp;
+ unsigned long rate;
+ int err, min_uV;
+
+ /* OPP usage is optional */
+ if (!dc->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);
+
+ 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 %lu Hz: %ld\n",
+ rate, PTR_ERR(opp));
+ return;
+ }
+
+ min_uV = dev_pm_opp_get_voltage(opp);
+ dev_pm_opp_put(opp);
+
+ /*
+ * Voltage scaling is optional and trying to set voltage for a dummy
+ * regulator will error out.
+ */
+ if (!device_property_present(dc->dev, "core-supply"))
+ return;
+
+ /*
+ * Note that the minimum core voltage depends on the pixel clock
+ * rate (which depends on internal clock divider of 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 are managing the
+ * voltage by ourselves.
+ */
+ err = regulator_set_voltage(dc->core_reg, min_uV, INT_MAX);
+ if (err)
+ dev_err(dc->dev, "failed to set CORE voltage to %duV: %d\n",
+ min_uV, err);
+}
+
static void tegra_dc_commit_state(struct tegra_dc *dc,
struct tegra_dc_state *state)
{
@@ -1738,6 +1791,8 @@ static void tegra_dc_commit_state(struct tegra_dc *dc,
if (err < 0)
dev_err(dc->dev, "failed to set clock %pC to %lu Hz: %d\n",
dc->clk, state->pclk, err);
+
+ tegra_dc_update_voltage_state(dc, state);
}

static void tegra_dc_stop(struct tegra_dc *dc)
@@ -2521,6 +2576,7 @@ static int tegra_dc_runtime_suspend(struct host1x_client *client)

clk_disable_unprepare(dc->clk);
pm_runtime_put_sync(dev);
+ regulator_disable(dc->core_reg);

return 0;
}
@@ -2531,10 +2587,16 @@ static int tegra_dc_runtime_resume(struct host1x_client *client)
struct device *dev = client->dev;
int err;

+ err = regulator_enable(dc->core_reg);
+ if (err < 0) {
+ dev_err(dev, "failed to enable CORE regulator: %d\n", err);
+ return err;
+ }
+
err = pm_runtime_get_sync(dev);
if (err < 0) {
dev_err(dev, "failed to get runtime PM: %d\n", err);
- return err;
+ goto disable_regulator;
}

if (dc->soc->has_powergate) {
@@ -2564,6 +2626,9 @@ static int tegra_dc_runtime_resume(struct host1x_client *client)
clk_disable_unprepare(dc->clk);
put_rpm:
pm_runtime_put_sync(dev);
+disable_regulator:
+ regulator_disable(dc->core_reg);
+
return err;
}

@@ -2879,6 +2944,72 @@ static int tegra_dc_couple(struct tegra_dc *dc)
return 0;
}

+static void tegra_dc_deinit_opp_table(void *data)
+{
+ struct tegra_dc *dc = data;
+
+ dev_pm_opp_of_remove_table(dc->dev);
+ dev_pm_opp_put_supported_hw(dc->opp_table);
+ dev_pm_opp_put_regulators(dc->opp_table);
+}
+
+static int devm_tegra_dc_opp_table_init(struct tegra_dc *dc)
+{
+ struct opp_table *hw_opp_table;
+ u32 hw_version;
+ int err;
+
+ /* voltage scaling is optional */
+ dc->core_reg = devm_regulator_get(dc->dev, "core");
+ if (IS_ERR(dc->core_reg))
+ return dev_err_probe(dc->dev, PTR_ERR(dc->core_reg),
+ "failed to get CORE regulator\n");
+
+ /* legacy device-trees don't have OPP table */
+ if (!device_property_present(dc->dev, "operating-points-v2"))
+ return 0;
+
+ dc->opp_table = dev_pm_opp_get_opp_table(dc->dev);
+ if (IS_ERR(dc->opp_table))
+ return dev_err_probe(dc->dev, PTR_ERR(dc->opp_table),
+ "failed to prepare OPP table\n");
+
+ if (of_machine_is_compatible("nvidia,tegra20"))
+ hw_version = BIT(tegra_sku_info.soc_process_id);
+ else
+ hw_version = BIT(tegra_sku_info.soc_speedo_id);
+
+ hw_opp_table = dev_pm_opp_set_supported_hw(dc->dev, &hw_version, 1);
+ err = PTR_ERR_OR_ZERO(hw_opp_table);
+ if (err) {
+ dev_err(dc->dev, "failed to set supported HW: %d\n", err);
+ goto put_table;
+ }
+
+ err = dev_pm_opp_of_add_table(dc->dev);
+ if (err) {
+ dev_err(dc->dev, "failed to add OPP table: %d\n", err);
+ goto put_hw;
+ }
+
+ err = devm_add_action(dc->dev, tegra_dc_deinit_opp_table, dc);
+ if (err)
+ goto remove_table;
+
+ dev_info(dc->dev, "OPP HW ver. 0x%x\n", hw_version);
+
+ return 0;
+
+remove_table:
+ dev_pm_opp_of_remove_table(dc->dev);
+put_hw:
+ dev_pm_opp_put_supported_hw(dc->opp_table);
+put_table:
+ dev_pm_opp_put_opp_table(dc->opp_table);
+
+ return err;
+}
+
static int tegra_dc_probe(struct platform_device *pdev)
{
struct tegra_dc *dc;
@@ -2937,6 +3068,10 @@ static int tegra_dc_probe(struct platform_device *pdev)
tegra_powergate_power_off(dc->powergate);
}

+ err = devm_tegra_dc_opp_table_init(dc);
+ if (err < 0)
+ return err;
+
dc->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(dc->regs))
return PTR_ERR(dc->regs);
@@ -3007,6 +3142,7 @@ struct platform_driver tegra_dc_driver = {
.driver = {
.name = "tegra-dc",
.of_match_table = tegra_dc_of_match,
+ .sync_state = tegra_soc_device_sync_state,
},
.probe = tegra_dc_probe,
.remove = tegra_dc_remove,
diff --git a/drivers/gpu/drm/tegra/dc.h b/drivers/gpu/drm/tegra/dc.h
index ba4ed35139fb..fd774fc5c2e4 100644
--- a/drivers/gpu/drm/tegra/dc.h
+++ b/drivers/gpu/drm/tegra/dc.h
@@ -13,6 +13,8 @@

#include "drm.h"

+struct opp_table;
+struct regulator;
struct tegra_output;

#define TEGRA_DC_LEGACY_PLANES_NUM 6
@@ -107,6 +109,9 @@ struct tegra_dc {
struct drm_info_list *debugfs_files;

const struct tegra_dc_soc_info *soc;
+
+ struct opp_table *opp_table;
+ struct regulator *core_reg;
};

static inline struct tegra_dc *
--
2.27.0