[v3,4/5] drivers: bus: add driver for initializing the SSC bus on (some) qcom SoCs

From: Michael Srba <Michael.Srba@seznam.cz>

 This patch adds bindings for the AHB bus which exposes the SCC 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 haxagon 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>
---
 CHANGES:
 - v2: none
 - v3: fix clang warning
---
 drivers/bus/Kconfig              |   6 +
 drivers/bus/Makefile             |   1 +
 drivers/bus/qcom-ssc-block-bus.c | 365 +++++++++++++++++++++++++++++++
 3 files changed, 372 insertions(+)
 create mode 100644 drivers/bus/qcom-ssc-block-bus.c

On Mon, Jan 24, 2022 at 4:21 AM <michael.srba@seznam.cz> wrote:
>
> From: Michael Srba <Michael.Srba@seznam.cz>
>
>  This patch adds bindings for the AHB bus which exposes the SCC 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 haxagon 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>
> ---
>  CHANGES:
>  - v2: none
>  - v3: fix clang warning
> ---
>  drivers/bus/Kconfig              |   6 +
>  drivers/bus/Makefile             |   1 +
>  drivers/bus/qcom-ssc-block-bus.c | 365 +++++++++++++++++++++++++++++++
>  3 files changed, 372 insertions(+)
>  create mode 100644 drivers/bus/qcom-ssc-block-bus.c
>
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 3c68e174a113..f2b2e3098491 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -173,6 +173,12 @@ config SUNXI_RSB
>           with various RSB based devices, such as AXP223, AXP8XX PMICs,
>           and AC100/AC200 ICs.
>
> +config QCOM_SSC_BLOCK_BUS
> +       bool "Qualcomm SSC Block Bus Init Driver"
> +         help
> +         Say y here to enable support for initializing the bus that connects the SSC block's internal
> +         bus to the cNoC on (some) qcom SoCs
> +
>  config TEGRA_ACONNECT
>         tristate "Tegra ACONNECT Bus Driver"
>         depends on ARCH_TEGRA_210_SOC
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index 52c2f35a26a9..e6756e83a9c4 100644
> --- a/drivers/bus/Makefile
> +++ b/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
> diff --git a/drivers/bus/qcom-ssc-block-bus.c b/drivers/bus/qcom-ssc-block-bus.c
> new file mode 100644
> index 000000000000..a93c7350a231
> --- /dev/null
> +++ b/drivers/bus/qcom-ssc-block-bus.c
> @@ -0,0 +1,365 @@
> +// 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
> +
> +static const char *qcom_ssc_block_pd_names[] = {
> +       "ssc_cx",
> +       "ssc_mx"
> +};
> +
> +struct qcom_ssc_block_bus_data {
> +       int num_pds;
> +       const char **pd_names;
> +       struct device *pds[ARRAY_SIZE(qcom_ssc_block_pd_names)];
> +       char __iomem *reg_mpm_sscaon_config0; // MPM - msm power manager; AON - always-on
> +       char __iomem *reg_mpm_sscaon_config1; // that's as much as we know about these
> +       struct regmap *halt_map;
> +       u32 ssc_axi_halt;
> +       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;
> +};
> +
> +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);
> +
> +       clk_prepare_enable(data->xo_clk);
> +       clk_prepare_enable(data->aggre2_clk);
> +
> +       clk_prepare_enable(data->gcc_im_sleep_clk);
> +
> +       reg32_clear_bits(data->reg_mpm_sscaon_config0, BIT(4) | BIT(5));
> +       reg32_clear_bits(data->reg_mpm_sscaon_config1, BIT(31));
> +
> +       clk_disable(data->aggre2_north_clk);
> +
> +       ret = reset_control_deassert(data->ssc_reset);
> +       if (ret) {
> +               dev_err(dev, "error deasserting ssc_reset: %d\n", ret);
> +               return ret;
> +       }
> +
> +       clk_prepare_enable(data->aggre2_north_clk);
> +
> +       ret = reset_control_deassert(data->ssc_bcr);
> +       if (ret) {
> +               dev_err(dev, "error deasserting ssc_bcr: %d\n", ret);
> +               return ret;
> +       }
> +
> +       regmap_write(data->halt_map, data->ssc_axi_halt + AXI_HALTREQ_REG, 0);
> +
> +       clk_prepare_enable(data->ssc_xo_clk);
> +
> +       clk_prepare_enable(data->ssc_ahbs_clk);
> +
> +       return 0;
> +}
> +
> +static int 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);
> +               return 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);
> +               return ret;
> +       }
> +
> +       clk_disable(data->gcc_im_sleep_clk);
> +
> +       clk_disable(data->aggre2_north_clk);
> +
> +       clk_disable(data->aggre2_clk);
> +       clk_disable(data->xo_clk);
> +
> +       return 0;
> +}
> +
> +
> +static int qcom_ssc_block_bus_pds_attach(struct device *dev, struct device **pds,
> +                                        const char **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;
> +
> +       if (np)
> +               of_platform_populate(np, NULL, NULL, &pdev->dev);

This is something that needs to be done all the way at the end. If you
fail to probe this device, how does it make sense to have its child
devices populated/available?

-Saravana

> +
> +       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);
> +
> +       ret = qcom_ssc_block_bus_pds_attach(&pdev->dev, data->pds, data->pd_names, data->num_pds);
> +       if (ret < 0) {
> +               dev_err(&pdev->dev, "error when attaching power domains: %d\n", ret);
> +               return ret;
> +       }
> +
> +       ret = qcom_ssc_block_bus_pds_enable(data->pds, data->num_pds);
> +       if (ret < 0) {
> +               dev_err(&pdev->dev, "error when enabling power domains: %d\n", ret);
> +               return ret;
> +       }
> +
> +       // the meaning of the bits in these two registers is sadly not documented,
> +       // the set/clear operations are just copying what qcom does
> +       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)) {
> +               ret = PTR_ERR(data->reg_mpm_sscaon_config0);
> +               dev_err(&pdev->dev, "failed to ioremap mpm_sscaon_config0 (err: %d)\n", ret);
> +               return ret;
> +       }
> +       res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mpm_sscaon_config0");
> +       data->reg_mpm_sscaon_config1 = devm_ioremap_resource(&pdev->dev, res);
> +       if (IS_ERR(data->reg_mpm_sscaon_config1)) {
> +               ret = PTR_ERR(data->reg_mpm_sscaon_config1);
> +               dev_err(&pdev->dev, "failed to ioremap mpm_sscaon_config1 (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->ssc_bcr = devm_reset_control_get_exclusive(&pdev->dev, "ssc_bcr");
> +       if (IS_ERR(data->ssc_bcr)) {
> +               ret = PTR_ERR(data->ssc_bcr);
> +               dev_err(&pdev->dev, "failed to acquire reset: scc_bcr (err: %d)\n", ret);
> +               return ret;
> +       }
> +       data->ssc_reset = devm_reset_control_get_exclusive(&pdev->dev, "ssc_reset");
> +       if (IS_ERR(data->ssc_reset)) {
> +               ret = PTR_ERR(data->ssc_reset);
> +               dev_err(&pdev->dev, "failed to acquire reset: ssc_reset: (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->xo_clk = devm_clk_get(&pdev->dev, "xo");
> +       if (IS_ERR(data->xo_clk)) {
> +               ret = PTR_ERR(data->xo_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: xo (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->aggre2_clk = devm_clk_get(&pdev->dev, "aggre2");
> +       if (IS_ERR(data->aggre2_clk)) {
> +               ret = PTR_ERR(data->aggre2_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: aggre2 (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->gcc_im_sleep_clk = devm_clk_get(&pdev->dev, "gcc_im_sleep");
> +       if (IS_ERR(data->gcc_im_sleep_clk)) {
> +               ret = PTR_ERR(data->gcc_im_sleep_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: gcc_im_sleep (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->aggre2_north_clk = devm_clk_get(&pdev->dev, "aggre2_north");
> +       if (IS_ERR(data->aggre2_north_clk)) {
> +               ret = PTR_ERR(data->aggre2_north_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: aggre2_north (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->ssc_xo_clk = devm_clk_get(&pdev->dev, "ssc_xo");
> +       if (IS_ERR(data->ssc_xo_clk)) {
> +               ret = PTR_ERR(data->ssc_xo_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: ssc_xo (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       data->ssc_ahbs_clk = devm_clk_get(&pdev->dev, "ssc_ahbs");
> +       if (IS_ERR(data->ssc_ahbs_clk)) {
> +               ret = PTR_ERR(data->ssc_ahbs_clk);
> +               if (ret != -EPROBE_DEFER)
> +                       dev_err(&pdev->dev, "Failed to get clock: ssc_ahbs (err: %d)\n", ret);
> +               return ret;
> +       }
> +
> +       ret = of_parse_phandle_with_fixed_args(pdev->dev.of_node, "qcom,halt-regs", 1, 0,
> +                                              &halt_args);
> +       if (ret < 0) {
> +               dev_err(&pdev->dev, "failed to parse qcom,halt-regs\n");
> +               return -EINVAL;
> +       }
> +
> +       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);
> +
> +       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");
> --
> 2.34.1
>