spi: spi-qcom-qspi: Use OPP API to set clk/perf state

QSPI needs to vote on a performance state of a power domain depending on
the clock rate. Add support for it by specifying the perf state/clock rate
as an OPP table in device tree.
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Mark Brown <broonie@kernel.org>
Cc: Alok Chauhan <alokc@codeaurora.org>
Cc: Akash Asthana <akashast@codeaurora.org>
Cc: linux-spi@vger.kernel.org
Link: https://lore.kernel.org/r/1593769293-6354-2-git-send-email-rnayak@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/spi/spi-qcom-qspi.c

@@ -9,6 +9,7 @@
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/pm_runtime.h>
+#include <linux/pm_opp.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/spi-mem.h>
 
@@ -141,6 +142,8 @@ struct qcom_qspi {
 	struct clk_bulk_data *clks;
 	struct qspi_xfer xfer;
 	struct icc_path *icc_path_cpu_to_qspi;
+	struct opp_table *opp_table;
+	bool has_opp_table;
 	/* Lock to protect data accessed by IRQs */
 	spinlock_t lock;
 };
@@ -238,7 +241,7 @@ static int qcom_qspi_transfer_one(struct spi_master *master,
 		speed_hz = xfer->speed_hz;
 
 	/* In regular operation (SBL_EN=1) core must be 4x transfer clock */
-	ret = clk_set_rate(ctrl->clks[QSPI_CLK_CORE].clk, speed_hz * 4);
+	ret = dev_pm_opp_set_rate(ctrl->dev, speed_hz * 4);
 	if (ret) {
 		dev_err(ctrl->dev, "Failed to set core clk %d\n", ret);
 		return ret;
@@ -519,6 +522,20 @@ static int qcom_qspi_probe(struct platform_device *pdev)
 	master->handle_err = qcom_qspi_handle_err;
 	master->auto_runtime_pm = true;
 
+	ctrl->opp_table = dev_pm_opp_set_clkname(&pdev->dev, "core");
+	if (IS_ERR(ctrl->opp_table)) {
+		ret = PTR_ERR(ctrl->opp_table);
+		goto exit_probe_master_put;
+	}
+	/* OPP table is optional */
+	ret = dev_pm_opp_of_add_table(&pdev->dev);
+	if (!ret) {
+		ctrl->has_opp_table = true;
+	} else if (ret != -ENODEV) {
+		dev_err(&pdev->dev, "invalid OPP table in device tree\n");
+		goto exit_probe_master_put;
+	}
+
 	pm_runtime_enable(dev);
 
 	ret = spi_register_master(master);
@@ -526,6 +543,9 @@ static int qcom_qspi_probe(struct platform_device *pdev)
 		return 0;
 
 	pm_runtime_disable(dev);
+	if (ctrl->has_opp_table)
+		dev_pm_opp_of_remove_table(&pdev->dev);
+	dev_pm_opp_put_clkname(ctrl->opp_table);
 
 exit_probe_master_put:
 	spi_master_put(master);
@@ -536,11 +556,15 @@ static int qcom_qspi_probe(struct platform_device *pdev)
 static int qcom_qspi_remove(struct platform_device *pdev)
 {
 	struct spi_master *master = platform_get_drvdata(pdev);
+	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
 
 	/* Unregister _before_ disabling pm_runtime() so we stop transfers */
 	spi_unregister_master(master);
 
 	pm_runtime_disable(&pdev->dev);
+	if (ctrl->has_opp_table)
+		dev_pm_opp_of_remove_table(&pdev->dev);
+	dev_pm_opp_put_clkname(ctrl->opp_table);
 
 	return 0;
 }
@@ -551,6 +575,8 @@ static int __maybe_unused qcom_qspi_runtime_suspend(struct device *dev)
 	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
 	int ret;
 
+	/* Drop the performance state vote */
+	dev_pm_opp_set_rate(dev, 0);
 	clk_bulk_disable_unprepare(QSPI_NUM_CLKS, ctrl->clks);
 
 	ret = icc_disable(ctrl->icc_path_cpu_to_qspi);