Re: [PATCH v5 7/7] clk: qcom: add the driver for the MSM8996 APCS clocks

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 27.01.2023 00:03, Dmitry Baryshkov wrote:
> Add a simple driver handling the APCS clocks on MSM8996. For now it
> supports just a single aux clock, linking GPLL0 to CPU and CBF clocks.
> 
> Note, there is little sense in registering sys_apcs_aux as a child of
> gpll0. The PLL is always-on. And listing the gpll0 as a property of the
> apcs would delay its probing until the GCC has been probed (while we
> would like for the apcs to be probed as early as possible).
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>

Konrad
>  drivers/clk/qcom/Makefile       |  2 +-
>  drivers/clk/qcom/apcs-msm8996.c | 88 +++++++++++++++++++++++++++++++++
>  2 files changed, 89 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/clk/qcom/apcs-msm8996.c
> 
> diff --git a/drivers/clk/qcom/Makefile b/drivers/clk/qcom/Makefile
> index 3194465dd02c..a8ed1f38b2f7 100644
> --- a/drivers/clk/qcom/Makefile
> +++ b/drivers/clk/qcom/Makefile
> @@ -52,7 +52,7 @@ obj-$(CONFIG_MSM_MMCC_8998) += mmcc-msm8998.o
>  obj-$(CONFIG_QCOM_A53PLL) += a53-pll.o
>  obj-$(CONFIG_QCOM_A7PLL) += a7-pll.o
>  obj-$(CONFIG_QCOM_CLK_APCS_MSM8916) += apcs-msm8916.o
> -obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += clk-cpu-8996.o
> +obj-$(CONFIG_QCOM_CLK_APCC_MSM8996) += apcs-msm8996.o clk-cpu-8996.o
>  obj-$(CONFIG_QCOM_CLK_APCS_SDX55) += apcs-sdx55.o
>  obj-$(CONFIG_QCOM_CLK_RPM) += clk-rpm.o
>  obj-$(CONFIG_QCOM_CLK_RPMH) += clk-rpmh.o
> diff --git a/drivers/clk/qcom/apcs-msm8996.c b/drivers/clk/qcom/apcs-msm8996.c
> new file mode 100644
> index 000000000000..48d22572b6ae
> --- /dev/null
> +++ b/drivers/clk/qcom/apcs-msm8996.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Qualcomm APCS clock controller driver
> + *
> + * Copyright (c) 2022, Linaro Limited
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> + */
> +
> +#include <linux/bits.h>
> +#include <linux/clk-provider.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +#define APCS_AUX_OFFSET	0x50
> +
> +#define APCS_AUX_DIV_MASK GENMASK(17, 16)
> +#define APCS_AUX_DIV_2 0x1
> +
> +static int qcom_apcs_msm8996_clk_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device *parent = dev->parent;
> +	struct regmap *regmap;
> +	struct clk_hw *hw;
> +	unsigned int val;
> +	int ret = -ENODEV;
> +
> +	regmap = dev_get_regmap(parent, NULL);
> +	if (!regmap) {
> +		dev_err(dev, "failed to get regmap: %d\n", ret);
> +		return ret;
> +	}
> +
> +	regmap_read(regmap, APCS_AUX_OFFSET, &val);
> +	regmap_update_bits(regmap, APCS_AUX_OFFSET, APCS_AUX_DIV_MASK,
> +			   FIELD_PREP(APCS_AUX_DIV_MASK, APCS_AUX_DIV_2));
> +
> +	/*
> +	 * This clock is used during CPU cluster setup while setting up CPU PLLs.
> +	 * Add hardware mandated delay to make sure that the sys_apcs_aux clock
> +	 * is stable (after setting the divider) before continuing
> +	 * bootstrapping to keep CPUs from ending up in a weird state.
> +	 */
> +	udelay(5);
> +
> +	/*
> +	 * As this clocks is a parent of the CPU cluster clocks and is actually
> +	 * used as a parent during CPU clocks setup, we want for it to gegister
> +	 * as early as possible, without letting fw_devlink to delay probing of
> +	 * either of the drivers.
> +	 *
> +	 * The sys_apcs_aux is a child (divider) of gpll0, but we register it
> +	 * as a fixed rate clock instead to ease bootstrapping procedure. By
> +	 * doing this we make sure that CPU cluster clocks are able to be setup
> +	 * early during the boot process (as it is recommended by Qualcomm).
> +	 */
> +	hw = devm_clk_hw_register_fixed_rate(dev, "sys_apcs_aux", NULL, 0, 300000000);
> +	if (IS_ERR(hw))
> +		return PTR_ERR(hw);
> +
> +	return devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, hw);
> +}
> +
> +static struct platform_driver qcom_apcs_msm8996_clk_driver = {
> +	.probe = qcom_apcs_msm8996_clk_probe,
> +	.driver = {
> +		.name = "qcom-apcs-msm8996-clk",
> +	},
> +};
> +
> +/* Register early enough to fix the clock to be used for other cores */
> +static int __init qcom_apcs_msm8996_clk_init(void)
> +{
> +	return platform_driver_register(&qcom_apcs_msm8996_clk_driver);
> +}
> +postcore_initcall(qcom_apcs_msm8996_clk_init);
> +
> +static void __exit qcom_apcs_msm8996_clk_exit(void)
> +{
> +	platform_driver_unregister(&qcom_apcs_msm8996_clk_driver);
> +}
> +module_exit(qcom_apcs_msm8996_clk_exit);
> +
> +MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Qualcomm MSM8996 APCS clock driver");