[PATCH v1 13/30] drm/tegra: gr2d: Support OPP and SoC core voltage scaling

[Dmitry Osipenko <digetx@gmail.com>]

Add OPP and SoC core voltage scaling support to the GR2D driver.
This is required for enabling system-wide DVFS on 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/gr2d.c | 136 +++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)

diff --git a/drivers/gpu/drm/tegra/gr2d.c b/drivers/gpu/drm/tegra/gr2d.c
index f30aa86e4c9f..6d8f9419d908 100644
--- a/drivers/gpu/drm/tegra/gr2d.c
+++ b/drivers/gpu/drm/tegra/gr2d.c
@@ -7,6 +7,9 @@
 #include <linux/iommu.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
+#include <linux/pm_opp.h>
+
+#include <soc/tegra/fuse.h>
 
 #include "drm.h"
 #include "gem.h"
@@ -185,6 +188,135 @@ static const u32 gr2d_addr_regs[] = {
 	GR2D_VA_BASE_ADDR_SB,
 };
 
+static int gr2d_init_opp_state(struct device *dev, struct gr2d *gr2d)
+{
+	struct dev_pm_opp *opp;
+	unsigned long rate;
+	int err;
+
+	/*
+	 * If voltage regulator presents, then we could select the fastest
+	 * clock rate, but driver doesn't support power management and
+	 * frequency scaling yet, hence the top freq OPP will vote for a
+	 * very high voltage that will produce lot's of heat.  Let's select
+	 * OPP for the current/default rate for now.
+	 *
+	 * Clock rate should be pre-initialized (i.e. it's non-zero) either
+	 * by clock driver or by assigned clocks in a device-tree.
+	 */
+	rate = clk_get_rate(gr2d->clk);
+
+	/* find suitable OPP for the clock rate supportable by SoC speedo ID */
+	opp = dev_pm_opp_find_freq_ceil(dev, &rate);
+
+	/*
+	 * dev_pm_opp_set_rate() doesn't search for a floor clock rate and it
+	 * will error out if default clock rate is too high, i.e. unsupported
+	 * by a SoC hardware version.  Hence will find floor rate by ourselves.
+	 */
+	if (opp == ERR_PTR(-ERANGE))
+		opp = dev_pm_opp_find_freq_floor(dev, &rate);
+
+	err = PTR_ERR_OR_ZERO(opp);
+	if (err) {
+		dev_err(dev, "failed to get OPP for %ld Hz: %d\n",
+			rate, err);
+		return err;
+	}
+
+	dev_pm_opp_put(opp);
+
+	/*
+	 * First dummy rate-set initializes voltage vote by setting voltage
+	 * in accordance to the clock rate.  We need to do this because GR2D
+	 * currently doesn't support power management and clock is permanently
+	 * enabled.
+	 */
+	err = dev_pm_opp_set_rate(dev, rate);
+	if (err) {
+		dev_err(dev, "failed to initialize OPP clock: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static void gr2d_deinit_opp_table(void *data)
+{
+	struct device *dev = data;
+	struct opp_table *opp_table;
+
+	opp_table = dev_pm_opp_get_opp_table(dev);
+	dev_pm_opp_of_remove_table(dev);
+	dev_pm_opp_put_supported_hw(opp_table);
+	dev_pm_opp_put_regulators(opp_table);
+	dev_pm_opp_put_opp_table(opp_table);
+}
+
+static int devm_gr2d_init_opp_table(struct device *dev, struct gr2d *gr2d)
+{
+	struct opp_table *opp_table, *hw_opp_table;
+	const char *rname = "core";
+	u32 hw_version;
+	int err;
+
+	/* voltage scaling is optional */
+	if (device_property_present(dev, "core-supply"))
+		opp_table = dev_pm_opp_set_regulators(dev, &rname, 1);
+	else
+		opp_table = dev_pm_opp_get_opp_table(dev);
+
+	if (IS_ERR(opp_table))
+		return dev_err_probe(dev, PTR_ERR(opp_table),
+				     "failed to prepare OPP table\n");
+
+	if (gr2d->soc->version == 0x20)
+		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(dev, &hw_version, 1);
+	err = PTR_ERR_OR_ZERO(hw_opp_table);
+	if (err) {
+		dev_err(dev, "failed to set supported HW: %d\n", err);
+		goto put_table;
+	}
+
+	/*
+	 * OPP table presence is optional and we want the set_rate() of OPP
+	 * API to work similarly to clk_set_rate() if table is missing in a
+	 * device-tree.  The add_table() errors out if OPP is missing in DT.
+	 */
+	if (device_property_present(dev, "operating-points-v2")) {
+		err = dev_pm_opp_of_add_table(dev);
+		if (err) {
+			dev_err(dev, "failed to add OPP table: %d\n", err);
+			goto put_hw;
+		}
+
+		err = gr2d_init_opp_state(dev, gr2d);
+		if (err)
+			goto remove_table;
+	}
+
+	err = devm_add_action(dev, gr2d_deinit_opp_table, dev);
+	if (err)
+		goto remove_table;
+
+	dev_info(dev, "OPP HW ver. 0x%x\n", hw_version);
+
+	return 0;
+
+remove_table:
+	dev_pm_opp_of_remove_table(dev);
+put_hw:
+	dev_pm_opp_put_supported_hw(opp_table);
+put_table:
+	dev_pm_opp_put_regulators(opp_table);
+
+	return err;
+}
+
 static int gr2d_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -209,6 +341,10 @@ static int gr2d_probe(struct platform_device *pdev)
 		return PTR_ERR(gr2d->clk);
 	}
 
+	err = devm_gr2d_init_opp_table(dev, gr2d);
+	if (err)
+		return dev_err_probe(dev, err, "failed to initialize OPP\n");
+
 	err = clk_prepare_enable(gr2d->clk);
 	if (err) {
 		dev_err(dev, "cannot turn on clock\n");
-- 
2.27.0