bus: add driver for initializing the SSC bus on (some) qcom SoCs

Add bindings for the AHB bus which exposes the SSC (Snapdragon Sensor Core)
block in the global address space. This bus (and the SSC block itself) is
present on certain qcom SoCs.

In typical configuration, this bus (as some of the clocks and registers
that we need to manipulate) is not accessible to Linux, and the resources
on this bus are indirectly accessed by communicating with a hexagon CPU
core residing in the SSC block. In this configuration, the hypervisor is
the one performing the bus initialization for the purposes of bringing
the hexagon CPU core out of reset.

However, it is possible to change the configuration, in which case this
driver will initialize the bus.

In combination with drivers for resources on the SSC bus, this driver can
aid in debugging, and for example with a TLMM driver can be used to
directly access SSC-dedicated GPIO pins, removing the need to commit
to a particular usecase during hw design.

Finally, until open firmware for the hexagon core is available, this
approach allows for using sensors hooked up to SSC-dedicated GPIO pins
on mainline Linux simply by utilizing the existing in-tree drivers for
these sensors.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220411072156.24451-5-michael.srba@seznam.cz

drivers/bus/Kconfig

@@ -152,6 +152,17 @@ config QCOM_EBI2
 	  Interface 2, which can be used to connect things like NAND Flash,
 	  SRAM, ethernet adapters, FPGAs and LCD displays.
 
+config QCOM_SSC_BLOCK_BUS
+	bool "Qualcomm SSC Block Bus Init Driver"
+	  depends on ARCH_QCOM
+	  help
+	  Say y here to enable support for initializing the bus that connects
+	  the SSC block's internal bus to the cNoC (configurantion NoC) on
+	  (some) qcom SoCs.
+	  The SSC (Snapdragon Sensor Core) block contains a gpio controller,
+	  i2c/spi/uart controllers, a hexagon core, and a clock controller
+	  which provides clocks for the above.
+
 config SUN50I_DE2_BUS
 	bool "Allwinner A64 DE2 Bus Driver"
 	  default ARM64

drivers/bus/Makefile

@@ -25,6 +25,7 @@ obj-$(CONFIG_OMAP_INTERCONNECT)	+= omap_l3_smx.o omap_l3_noc.o
 
 obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
 obj-$(CONFIG_QCOM_EBI2)		+= qcom-ebi2.o
+obj-$(CONFIG_QCOM_SSC_BLOCK_BUS)	+= qcom-ssc-block-bus.o
 obj-$(CONFIG_SUN50I_DE2_BUS)	+= sun50i-de2.o
 obj-$(CONFIG_SUNXI_RSB)		+= sunxi-rsb.o
 obj-$(CONFIG_OF)		+= simple-pm-bus.o

drivers/bus/qcom-ssc-block-bus.c

@@ -0,0 +1,389 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) 2021, Michael Srba
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_clock.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+
+/* AXI Halt Register Offsets */
+#define AXI_HALTREQ_REG			0x0
+#define AXI_HALTACK_REG			0x4
+#define AXI_IDLE_REG			0x8
+
+#define SSCAON_CONFIG0_CLAMP_EN_OVRD		BIT(4)
+#define SSCAON_CONFIG0_CLAMP_EN_OVRD_VAL	BIT(5)
+
+static const char *const qcom_ssc_block_pd_names[] = {
+	"ssc_cx",
+	"ssc_mx"
+};
+
+struct qcom_ssc_block_bus_data {
+	const char *const *pd_names;
+	struct device *pds[ARRAY_SIZE(qcom_ssc_block_pd_names)];
+	char __iomem *reg_mpm_sscaon_config0;
+	char __iomem *reg_mpm_sscaon_config1;
+	struct regmap *halt_map;
+	struct clk *xo_clk;
+	struct clk *aggre2_clk;
+	struct clk *gcc_im_sleep_clk;
+	struct clk *aggre2_north_clk;
+	struct clk *ssc_xo_clk;
+	struct clk *ssc_ahbs_clk;
+	struct reset_control *ssc_bcr;
+	struct reset_control *ssc_reset;
+	u32 ssc_axi_halt;
+	int num_pds;
+};
+
+static void reg32_set_bits(char __iomem *reg, u32 value)
+{
+	u32 tmp = ioread32(reg);
+
+	iowrite32(tmp | value, reg);
+}
+
+static void reg32_clear_bits(char __iomem *reg, u32 value)
+{
+	u32 tmp = ioread32(reg);
+
+	iowrite32(tmp & (~value), reg);
+}
+
+static int qcom_ssc_block_bus_init(struct device *dev)
+{
+	int ret;
+
+	struct qcom_ssc_block_bus_data *data = dev_get_drvdata(dev);
+
+	ret = clk_prepare_enable(data->xo_clk);
+	if (ret) {
+		dev_err(dev, "error enabling xo_clk: %d\n", ret);
+		goto err_xo_clk;
+	}
+
+	ret = clk_prepare_enable(data->aggre2_clk);
+	if (ret) {
+		dev_err(dev, "error enabling aggre2_clk: %d\n", ret);
+		goto err_aggre2_clk;
+	}
+
+	ret = clk_prepare_enable(data->gcc_im_sleep_clk);
+	if (ret) {
+		dev_err(dev, "error enabling gcc_im_sleep_clk: %d\n", ret);
+		goto err_gcc_im_sleep_clk;
+	}
+
+	/*
+	 * We need to intervene here because the HW logic driving these signals cannot handle
+	 * initialization after power collapse by itself.
+	 */
+	reg32_clear_bits(data->reg_mpm_sscaon_config0,
+			 SSCAON_CONFIG0_CLAMP_EN_OVRD | SSCAON_CONFIG0_CLAMP_EN_OVRD_VAL);
+	/* override few_ack/rest_ack */
+	reg32_clear_bits(data->reg_mpm_sscaon_config1, BIT(31));
+
+	ret = clk_prepare_enable(data->aggre2_north_clk);
+	if (ret) {
+		dev_err(dev, "error enabling aggre2_north_clk: %d\n", ret);
+		goto err_aggre2_north_clk;
+	}
+
+	ret = reset_control_deassert(data->ssc_reset);
+	if (ret) {
+		dev_err(dev, "error deasserting ssc_reset: %d\n", ret);
+		goto err_ssc_reset;
+	}
+
+	ret = reset_control_deassert(data->ssc_bcr);
+	if (ret) {
+		dev_err(dev, "error deasserting ssc_bcr: %d\n", ret);
+		goto err_ssc_bcr;
+	}
+
+	regmap_write(data->halt_map, data->ssc_axi_halt + AXI_HALTREQ_REG, 0);
+
+	ret = clk_prepare_enable(data->ssc_xo_clk);
+	if (ret) {
+		dev_err(dev, "error deasserting ssc_xo_clk: %d\n", ret);
+		goto err_ssc_xo_clk;
+	}
+
+	ret = clk_prepare_enable(data->ssc_ahbs_clk);
+	if (ret) {
+		dev_err(dev, "error deasserting ssc_ahbs_clk: %d\n", ret);
+		goto err_ssc_ahbs_clk;
+	}
+
+	return 0;
+
+err_ssc_ahbs_clk:
+	clk_disable(data->ssc_xo_clk);
+
+err_ssc_xo_clk:
+	regmap_write(data->halt_map, data->ssc_axi_halt + AXI_HALTREQ_REG, 1);
+
+	reset_control_assert(data->ssc_bcr);
+
+err_ssc_bcr:
+	reset_control_assert(data->ssc_reset);
+
+err_ssc_reset:
+	clk_disable(data->aggre2_north_clk);
+
+err_aggre2_north_clk:
+	reg32_set_bits(data->reg_mpm_sscaon_config0, BIT(4) | BIT(5));
+	reg32_set_bits(data->reg_mpm_sscaon_config1, BIT(31));
+
+	clk_disable(data->gcc_im_sleep_clk);
+
+err_gcc_im_sleep_clk:
+	clk_disable(data->aggre2_clk);
+
+err_aggre2_clk:
+	clk_disable(data->xo_clk);
+
+err_xo_clk:
+	return ret;
+}
+
+static void qcom_ssc_block_bus_deinit(struct device *dev)
+{
+	int ret;
+
+	struct qcom_ssc_block_bus_data *data = dev_get_drvdata(dev);
+
+	clk_disable(data->ssc_xo_clk);
+	clk_disable(data->ssc_ahbs_clk);
+
+	ret = reset_control_assert(data->ssc_bcr);
+	if (ret)
+		dev_err(dev, "error asserting ssc_bcr: %d\n", ret);
+
+	regmap_write(data->halt_map, data->ssc_axi_halt + AXI_HALTREQ_REG, 1);
+
+	reg32_set_bits(data->reg_mpm_sscaon_config1, BIT(31));
+	reg32_set_bits(data->reg_mpm_sscaon_config0, BIT(4) | BIT(5));
+
+	ret = reset_control_assert(data->ssc_reset);
+	if (ret)
+		dev_err(dev, "error asserting ssc_reset: %d\n", ret);
+
+	clk_disable(data->gcc_im_sleep_clk);
+
+	clk_disable(data->aggre2_north_clk);
+
+	clk_disable(data->aggre2_clk);
+	clk_disable(data->xo_clk);
+}
+
+static int qcom_ssc_block_bus_pds_attach(struct device *dev, struct device **pds,
+					 const char *const *pd_names, size_t num_pds)
+{
+	int ret;
+	int i;
+
+	for (i = 0; i < num_pds; i++) {
+		pds[i] = dev_pm_domain_attach_by_name(dev, pd_names[i]);
+		if (IS_ERR_OR_NULL(pds[i])) {
+			ret = PTR_ERR(pds[i]) ? : -ENODATA;
+			goto unroll_attach;
+		}
+	}
+
+	return num_pds;
+
+unroll_attach:
+	for (i--; i >= 0; i--)
+		dev_pm_domain_detach(pds[i], false);
+
+	return ret;
+};
+
+static void qcom_ssc_block_bus_pds_detach(struct device *dev, struct device **pds, size_t num_pds)
+{
+	int i;
+
+	for (i = 0; i < num_pds; i++)
+		dev_pm_domain_detach(pds[i], false);
+}
+
+static int qcom_ssc_block_bus_pds_enable(struct device **pds, size_t num_pds)
+{
+	int ret;
+	int i;
+
+	for (i = 0; i < num_pds; i++) {
+		dev_pm_genpd_set_performance_state(pds[i], INT_MAX);
+		ret = pm_runtime_get_sync(pds[i]);
+		if (ret < 0)
+			goto unroll_pd_votes;
+	}
+
+	return 0;
+
+unroll_pd_votes:
+	for (i--; i >= 0; i--) {
+		dev_pm_genpd_set_performance_state(pds[i], 0);
+		pm_runtime_put(pds[i]);
+	}
+
+	return ret;
+};
+
+static void qcom_ssc_block_bus_pds_disable(struct device **pds, size_t num_pds)
+{
+	int i;
+
+	for (i = 0; i < num_pds; i++) {
+		dev_pm_genpd_set_performance_state(pds[i], 0);
+		pm_runtime_put(pds[i]);
+	}
+}
+
+static int qcom_ssc_block_bus_probe(struct platform_device *pdev)
+{
+	struct qcom_ssc_block_bus_data *data;
+	struct device_node *np = pdev->dev.of_node;
+	struct of_phandle_args halt_args;
+	struct resource *res;
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, data);
+
+	data->pd_names = qcom_ssc_block_pd_names;
+	data->num_pds = ARRAY_SIZE(qcom_ssc_block_pd_names);
+
+	/* power domains */
+	ret = qcom_ssc_block_bus_pds_attach(&pdev->dev, data->pds, data->pd_names, data->num_pds);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "error when attaching power domains\n");
+
+	ret = qcom_ssc_block_bus_pds_enable(data->pds, data->num_pds);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "error when enabling power domains\n");
+
+	/* low level overrides for when the HW logic doesn't "just work" */
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mpm_sscaon_config0");
+	data->reg_mpm_sscaon_config0 = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->reg_mpm_sscaon_config0))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->reg_mpm_sscaon_config0),
+				     "Failed to ioremap mpm_sscaon_config0\n");
+
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mpm_sscaon_config1");
+	data->reg_mpm_sscaon_config1 = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->reg_mpm_sscaon_config1))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->reg_mpm_sscaon_config1),
+				     "Failed to ioremap mpm_sscaon_config1\n");
+
+	/* resets */
+	data->ssc_bcr = devm_reset_control_get_exclusive(&pdev->dev, "ssc_bcr");
+	if (IS_ERR(data->ssc_bcr))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->ssc_bcr),
+				     "Failed to acquire reset: scc_bcr\n");
+
+	data->ssc_reset = devm_reset_control_get_exclusive(&pdev->dev, "ssc_reset");
+	if (IS_ERR(data->ssc_reset))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->ssc_reset),
+				     "Failed to acquire reset: ssc_reset:\n");
+
+	/* clocks */
+	data->xo_clk = devm_clk_get(&pdev->dev, "xo");
+	if (IS_ERR(data->xo_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->xo_clk),
+				     "Failed to get clock: xo\n");
+
+	data->aggre2_clk = devm_clk_get(&pdev->dev, "aggre2");
+	if (IS_ERR(data->aggre2_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->aggre2_clk),
+				     "Failed to get clock: aggre2\n");
+
+	data->gcc_im_sleep_clk = devm_clk_get(&pdev->dev, "gcc_im_sleep");
+	if (IS_ERR(data->gcc_im_sleep_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->gcc_im_sleep_clk),
+				     "Failed to get clock: gcc_im_sleep\n");
+
+	data->aggre2_north_clk = devm_clk_get(&pdev->dev, "aggre2_north");
+	if (IS_ERR(data->aggre2_north_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->aggre2_north_clk),
+				     "Failed to get clock: aggre2_north\n");
+
+	data->ssc_xo_clk = devm_clk_get(&pdev->dev, "ssc_xo");
+	if (IS_ERR(data->ssc_xo_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->ssc_xo_clk),
+				     "Failed to get clock: ssc_xo\n");
+
+	data->ssc_ahbs_clk = devm_clk_get(&pdev->dev, "ssc_ahbs");
+	if (IS_ERR(data->ssc_ahbs_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(data->ssc_ahbs_clk),
+				     "Failed to get clock: ssc_ahbs\n");
+
+	ret = of_parse_phandle_with_fixed_args(pdev->dev.of_node, "qcom,halt-regs", 1, 0,
+					       &halt_args);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "Failed to parse qcom,halt-regs\n");
+
+	data->halt_map = syscon_node_to_regmap(halt_args.np);
+	of_node_put(halt_args.np);
+	if (IS_ERR(data->halt_map))
+		return PTR_ERR(data->halt_map);
+
+	data->ssc_axi_halt = halt_args.args[0];
+
+	qcom_ssc_block_bus_init(&pdev->dev);
+
+	of_platform_populate(np, NULL, NULL, &pdev->dev);
+
+	return 0;
+}
+
+static int qcom_ssc_block_bus_remove(struct platform_device *pdev)
+{
+	struct qcom_ssc_block_bus_data *data = platform_get_drvdata(pdev);
+
+	qcom_ssc_block_bus_deinit(&pdev->dev);
+
+	iounmap(data->reg_mpm_sscaon_config0);
+	iounmap(data->reg_mpm_sscaon_config1);
+
+	qcom_ssc_block_bus_pds_disable(data->pds, data->num_pds);
+	qcom_ssc_block_bus_pds_detach(&pdev->dev, data->pds, data->num_pds);
+	pm_runtime_disable(&pdev->dev);
+	pm_clk_destroy(&pdev->dev);
+
+	return 0;
+}
+
+static const struct of_device_id qcom_ssc_block_bus_of_match[] = {
+	{ .compatible = "qcom,ssc-block-bus", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, qcom_ssc_block_bus_of_match);
+
+static struct platform_driver qcom_ssc_block_bus_driver = {
+	.probe = qcom_ssc_block_bus_probe,
+	.remove = qcom_ssc_block_bus_remove,
+	.driver = {
+		.name = "qcom-ssc-block-bus",
+		.of_match_table = qcom_ssc_block_bus_of_match,
+	},
+};
+
+module_platform_driver(qcom_ssc_block_bus_driver);
+
+MODULE_DESCRIPTION("A driver for handling the init sequence needed for accessing the SSC block on (some) qcom SoCs over AHB");
+MODULE_AUTHOR("Michael Srba <Michael.Srba@seznam.cz>");
+MODULE_LICENSE("GPL v2");