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Subject: Re: [PATCH V2 3/4] soc: imx: Add generic blk-ctl driver
To:     Lucas Stach <l.stach@pengutronix.de>, robh+dt@kernel.org,
        shawnguo@kernel.org, s.hauer@pengutronix.de
Cc:     kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com,
        p.zabel@pengutronix.de, krzk@kernel.org, agx@sigxcpu.org,
        marex@denx.de, andrew.smirnov@gmail.com,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, ping.bai@nxp.com,
        frieder.schrempf@kontron.de, aford173@gmail.com, abel.vesa@nxp.com,
        Peng Fan <peng.fan@nxp.com>
References: <20210430052746.10815-1-peng.fan@oss.nxp.com>
 <20210430052746.10815-4-peng.fan@oss.nxp.com>
 <6997abd422ffa1fa384a048552109aec1095abc3.camel@pengutronix.de>
From:   "Peng Fan (OSS)" <peng.fan@oss.nxp.com>
Message-ID: <1707a917-5f91-b3e8-2be1-6461fb4c950c@oss.nxp.com>
Date:   Tue, 4 May 2021 18:30:52 +0800
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On 2021/5/4 17:47, Lucas Stach wrote:
> Am Freitag, dem 30.04.2021 um 13:27 +0800 schrieb Peng Fan (OSS):
>> From: Peng Fan <peng.fan@nxp.com>
>>
>> The i.MX8MM introduces an IP named BLK_CTL and usually is comprised of
>> some GPRs.
>>
>> The GPRs has some clock bits and reset bits, but here we take it
>> as virtual PDs, because of the clock and power domain A/B lock issue
>> when taking it as a clock controller.
>>
>> For some bits, it might be good to also make it as a reset controller,
>> but to i.MX8MM, we not add that support for now.
>>
>> Signed-off-by: Peng Fan <peng.fan@nxp.com>
>> ---
>>   drivers/soc/imx/Makefile  |   2 +-
>>   drivers/soc/imx/blk-ctl.c | 303 ++++++++++++++++++++++++++++++++++++++
>>   drivers/soc/imx/blk-ctl.h |  76 ++++++++++
>>   3 files changed, 380 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/soc/imx/blk-ctl.c
>>   create mode 100644 drivers/soc/imx/blk-ctl.h
>>
>> diff --git a/drivers/soc/imx/Makefile b/drivers/soc/imx/Makefile
>> index 078dc918f4f3..d3d2b49a386c 100644
>> --- a/drivers/soc/imx/Makefile
>> +++ b/drivers/soc/imx/Makefile
>> @@ -4,4 +4,4 @@ obj-$(CONFIG_ARCH_MXC) += soc-imx.o
>>   endif
>>   obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
>>   obj-$(CONFIG_IMX_GPCV2_PM_DOMAINS) += gpcv2.o
>> -obj-$(CONFIG_SOC_IMX8M) += soc-imx8m.o
>> +obj-$(CONFIG_SOC_IMX8M) += soc-imx8m.o blk-ctl.o
>> diff --git a/drivers/soc/imx/blk-ctl.c b/drivers/soc/imx/blk-ctl.c
>> new file mode 100644
>> index 000000000000..1f764dfd308d
>> --- /dev/null
>> +++ b/drivers/soc/imx/blk-ctl.c
>> @@ -0,0 +1,303 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright 2021 NXP.
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/err.h>
>> +#include <linux/io.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/regmap.h>
>> +#include <linux/slab.h>
>> +#include <linux/string.h>
>> +#include <linux/types.h>
>> +#include <linux/pm_domain.h>
>> +#include <linux/reset-controller.h>
>> +
>> +#include "blk-ctl.h"
>> +
>> +static inline struct imx_blk_ctl_domain *to_imx_blk_ctl_pd(struct generic_pm_domain *genpd)
>> +{
>> +	return container_of(genpd, struct imx_blk_ctl_domain, pd);
>> +}
>> +
>> +static int imx_blk_ctl_enable_hsk(struct device *dev)
>> +{
>> +	struct imx_blk_ctl *blk_ctl = dev_get_drvdata(dev);
>> +	const struct imx_blk_ctl_hw *hw = &blk_ctl->dev_data->hw_hsk;
>> +	struct regmap *regmap = blk_ctl->regmap;
>> +	int ret;
>> +
>> +
>> +	if (hw->flags & IMX_BLK_CTL_PD_RESET)
>> +		ret = regmap_update_bits(regmap, hw->rst_offset, hw->rst_mask, hw->rst_mask);
>> +
>> +	ret = regmap_update_bits(regmap, hw->offset, hw->mask, hw->mask);
>> +
>> +	/* Wait for handshake */
>> +	udelay(5);
>> +
>> +	return ret;
>> +}
>> +
>> +int imx_blk_ctl_power_off(struct generic_pm_domain *domain)
>> +{
>> +	struct imx_blk_ctl_domain *pd;
>> +	struct imx_blk_ctl *blk_ctl;
>> +	const struct imx_blk_ctl_hw *hw;
>> +	struct regmap *regmap;
>> +	int ret;
>> +
>> +	pd = to_imx_blk_ctl_pd(domain);
>> +	blk_ctl = pd->blk_ctl;
>> +	regmap = blk_ctl->regmap;
>> +	hw = &blk_ctl->dev_data->pds[pd->id];
>> +
>> +	ret = clk_bulk_prepare_enable(blk_ctl->num_clks, blk_ctl->clks);
>> +	if (ret)
>> +		return ret;
> 
> This looks a bit strange to me. Does that mean that you keep all the
> CCM clocks going into the blkctl enabled as long as one of the blkctl
> virtual power domains is up?

No. The clocks are disable unprepared when this function finish.
The clocks are only used for setting blk ctl bits and handshake.

  I would have expected each virtual PD to
> have a list of clock names that need to be enabled, to make this more
> selective.
> 
> I haven't completely thought it through if this is a problem, but I
> could see some CCM PLLs running without a reason if all CCM clocks are
> kept enabled. This surely is something we want to avoid from a pwoer
> consumption PoV.

I thought to add selective clocks for each virtual PD, but that makes
the design completed, and the clocks(gate) are only enabled for a little
while, so I think compared with the software complexity, the little
benifit of power could be ignored?

> 
>> +
>> +	ret = regmap_update_bits(regmap, hw->offset, hw->mask, 0);
>> +	if (ret)
>> +		goto hsk_fail;
>> +
>> +	if (hw->flags & IMX_BLK_CTL_PD_RESET)
>> +		ret = regmap_update_bits(regmap, hw->rst_offset, hw->rst_mask, 0);
>> +
>> +	if (atomic_dec_and_test(&blk_ctl->power_count)) {
>> +		ret = imx_blk_ctl_enable_hsk(blk_ctl->dev);
>> +		if (ret) {
>> +			dev_err(blk_ctl->dev, "Hankshake fail\n");
>> +			goto hsk_fail;
>> +		}
>> +	}
>> +
>> +hsk_fail:
>> +	clk_bulk_disable_unprepare(blk_ctl->num_clks, blk_ctl->clks);
>> +
>> +	return ret;
>> +}
>> +
>> +int imx_blk_ctl_power_on(struct generic_pm_domain *domain)
>> +{
>> +	struct imx_blk_ctl_domain *pd;
>> +	struct regmap *regmap;
>> +	const struct imx_blk_ctl_hw *hw;
>> +	int ret;
>> +	struct imx_blk_ctl *blk_ctl;
>> +
>> +	pd = to_imx_blk_ctl_pd(domain);
>> +	blk_ctl = pd->blk_ctl;
>> +	regmap = blk_ctl->regmap;
>> +	hw = &blk_ctl->dev_data->pds[pd->id];
>> +
>> +	ret = clk_bulk_prepare_enable(blk_ctl->num_clks, blk_ctl->clks);
>> +	if (ret)
>> +		return ret;
>> +
>> +	if ((atomic_read(&blk_ctl->power_count) == 0)) {
>> +		ret = imx_blk_ctl_enable_hsk(blk_ctl->dev);
>> +		if (ret) {
>> +			dev_err(blk_ctl->dev, "Hankshake fail\n");
>> +			goto disable_clk;
>> +		}
>> +	}
> 
> This is bogus. The variable isn't used as a atomic, if at all this
> should use atomic_inc_return, but I think even that isn't correct in
> that case. imx_blk_ctl_enable_hsk() includes a wait time, so if two
> paths call this function at the same time, the second caller would be
> able to overtake the first one, which is still waiting for the
> handshake to complete, effectively skipping the handshake. This needs a
> proper lock, as this function isn't called from a performance critical
> path it makes no sense to try to optimize this with an atomic counter,
> rather than going with a mutex.

I see. Will use a mutex here.

> 
>> +
>> +	if (hw->flags & IMX_BLK_CTL_PD_RESET)
>> +		ret = regmap_update_bits(regmap, hw->rst_offset, hw->rst_mask, 0);
>> +
>> +	/* Wait for reset propagate */
>> +	udelay(5);
>> +
>> +	if (hw->flags & IMX_BLK_CTL_PD_RESET)
>> +		ret = regmap_update_bits(regmap, hw->rst_offset, hw->rst_mask, hw->rst_mask);
>> +
>> +	ret = regmap_update_bits(regmap, hw->offset, hw->mask, hw->mask);
>> +	if (ret)
>> +		goto disable_clk;
>> +
>> +	atomic_inc(&blk_ctl->power_count);
>> +
>> +disable_clk:
>> +	clk_bulk_disable_unprepare(blk_ctl->num_clks, blk_ctl->clks);
>> +
>> +	return ret;
>> +}
>> +
>> +static int imx_blk_ctl_attach_pd(struct device *dev, struct device **devs, char **pd_names,
>> +				 u32 num_pds)
>> +{
>> +	int i, ret;
>> +
>> +	if (!pd_names)
>> +		return 0;
>> +
>> +	if (dev->pm_domain) {
>> +		devs[0] = dev;
>> +		pm_runtime_enable(dev);
>> +		return 0;
>> +	}
>> +
>> +	for (i = 0; i < num_pds; i++) {
>> +		devs[i] = dev_pm_domain_attach_by_name(dev, pd_names[i]);
>> +		if (IS_ERR_OR_NULL(devs[i])) {
>> +			ret = PTR_ERR(devs[i]) ? : -ENODATA;
>> +			goto detach_pm;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +
>> +detach_pm:
>> +	for (i--; i >= 0; i--)
>> +		dev_pm_domain_detach(devs[i], false);
>> +
>> +	return ret;
>> +}
>> +
>> +static int imx_blk_ctl_register_pd(struct device *dev)
>> +{
>> +	struct imx_blk_ctl *blk_ctl = dev_get_drvdata(dev);
>> +	const struct imx_blk_ctl_dev_data *dev_data = blk_ctl->dev_data;
>> +	int num = dev_data->pds_num;
>> +	struct imx_blk_ctl_domain *domain;
>> +	int i, ret;
>> +
>> +	blk_ctl->onecell_data.num_domains = num;
>> +	blk_ctl->onecell_data.domains = devm_kcalloc(dev, num,
>> +						     sizeof(struct generic_pm_domain *),
>> +						     GFP_KERNEL);
>> +
>> +	if (!blk_ctl->onecell_data.domains)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < num; i++) {
>> +		domain = devm_kzalloc(dev, sizeof(*domain), GFP_KERNEL);
>> +		if (!domain) {
>> +			ret = -ENOMEM;
>> +			goto remove_genpd;
>> +		}
>> +		domain->pd.name = dev_data->pds[i].name;
>> +		domain->pd.power_off = imx_blk_ctl_power_off;
>> +		domain->pd.power_on = imx_blk_ctl_power_on;
>> +		domain->blk_ctl = blk_ctl;
>> +		domain->id = i;
>> +
>> +		ret = pm_genpd_init(&domain->pd, NULL, true);
>> +		if (ret)
>> +			return ret;
>> +
>> +		blk_ctl->onecell_data.domains[i] = &domain->pd;
>> +	}
>> +
>> +	return 0;
>> +
>> +remove_genpd:
>> +	for (i = i - 1; i >= 0; i--)
>> +		pm_genpd_remove(blk_ctl->onecell_data.domains[i]);
>> +
>> +	return ret;
>> +}
>> +
>> +static int imx_blk_ctl_hook_pd(struct device *dev)
>> +{
>> +	struct imx_blk_ctl *blk_ctl = dev_get_drvdata(dev);
>> +	const struct imx_blk_ctl_dev_data *dev_data = blk_ctl->dev_data;
>> +	const struct imx_blk_ctl_hw *pds = dev_data->pds;
>> +	int num_active_pd = dev_data->num_active_pd;
>> +	int num = dev_data->pds_num;
>> +	struct generic_pm_domain *genpd, *child_genpd;
>> +	int ret;
>> +	int i, j;
>> +
>> +	blk_ctl->active_pds = devm_kcalloc(dev, num_active_pd, sizeof(struct device *), GFP_KERNEL);
>> +	if (!blk_ctl->active_pds)
>> +		return -ENOMEM;
>> +
>> +	ret = imx_blk_ctl_attach_pd(dev, blk_ctl->active_pds, dev_data->active_pd_names,
>> +				    num_active_pd);
>> +	if (ret) {
>> +		if (ret == -EPROBE_DEFER)
>> +			return ret;
>> +		dev_err(dev, "Failed to attach active pd: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	for (i = 0; i < num; i++) {
>> +		for (j = 0; j < num_active_pd; j++) {
>> +			genpd = pd_to_genpd(blk_ctl->active_pds[j]->pm_domain);
>> +			if (!strcmp(genpd->name, pds[i].parent_name))
>> +				break;
>> +		}
>> +
>> +		child_genpd = blk_ctl->onecell_data.domains[i];
>> +		if (pm_genpd_add_subdomain(genpd, child_genpd))
>> +			pr_warn("failed to add subdomain:\n");
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +int imx_blk_ctl_register(struct device *dev)
>> +{
>> +	struct imx_blk_ctl *blk_ctl = dev_get_drvdata(dev);
>> +	const struct imx_blk_ctl_dev_data *dev_data = blk_ctl->dev_data;
>> +	int num = dev_data->pds_num;
>> +	int i, ret;
>> +
>> +	if (!blk_ctl)
>> +		return -ENODEV;
>> +
>> +	ret = imx_blk_ctl_register_pd(dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = imx_blk_ctl_hook_pd(dev);
>> +	if (ret)
>> +		goto unregister_pd;
>> +
>> +	ret = of_genpd_add_provider_onecell(dev->of_node, &blk_ctl->onecell_data);
>> +	if (ret)
>> +		goto detach_pd;
>> +
>> +	pm_runtime_get_noresume(dev);
>> +	pm_runtime_set_active(dev);
>> +	pm_runtime_enable(dev);
>> +
>> +	pm_runtime_put(dev);
>> +
>> +	return 0;
>> +
>> +detach_pd:
>> +	for (i = blk_ctl->dev_data->num_active_pd; i >= 0; i--)
>> +		dev_pm_domain_detach(blk_ctl->active_pds[i], false);
>> +unregister_pd:
>> +	for (i = num - 1; i >= 0; i--)
>> +		pm_genpd_remove(blk_ctl->onecell_data.domains[i]);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(imx_blk_ctl_register);
>> +
>> +static int __maybe_unused imx_blk_ctl_runtime_suspend(struct device *dev)
>> +{
>> +	return 0;
>> +}
>> +
>> +static int __maybe_unused imx_blk_ctl_runtime_resume(struct device *dev)
>> +{
>> +	return 0;
>> +}
> 
> Why those empty stubs? If you don't need to do anything for
> suspend/resume, just don't add the functions.

ok, will drop in V3.

Thanks,
Peng.

> 
>> +
>> +const struct dev_pm_ops imx_blk_ctl_pm_ops = {
>> +	SET_RUNTIME_PM_OPS(imx_blk_ctl_runtime_suspend,
>> +			   imx_blk_ctl_runtime_resume, NULL)
>> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>> +			   pm_runtime_force_resume)
>> +};
>> +EXPORT_SYMBOL_GPL(imx_blk_ctl_pm_ops);
>> diff --git a/drivers/soc/imx/blk-ctl.h b/drivers/soc/imx/blk-ctl.h
>> new file mode 100644
>> index 000000000000..e736369406a1
>> --- /dev/null
>> +++ b/drivers/soc/imx/blk-ctl.h
>> @@ -0,0 +1,76 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef __SOC_IMX_BLK_CTL_H
>> +#define __SOC_IMX_BLK_CTL_H
>> +
>> +enum imx_blk_ctl_pd_type {
>> +	BLK_CTL_PD,
>> +};
>> +
>> +struct imx_blk_ctl_hw {
>> +	int type;
>> +	char *name;
>> +	char *parent_name;
>> +	u32 offset;
>> +	u32 mask;
>> +	u32 flags;
>> +	u32 id;
>> +	u32 rst_offset;
>> +	u32 rst_mask;
>> +};
>> +
>> +struct imx_blk_ctl_domain {
>> +	struct generic_pm_domain pd;
>> +	struct imx_blk_ctl *blk_ctl;
>> +	u32 id;
>> +};
>> +
>> +struct imx_blk_ctl_dev_data {
>> +	struct regmap_config config;
>> +	struct imx_blk_ctl_hw *pds;
>> +	struct imx_blk_ctl_hw hw_hsk;
>> +	u32 pds_num;
>> +	char **active_pd_names;
>> +	u32 num_active_pd;
>> +};
>> +
>> +struct imx_blk_ctl {
>> +	struct device *dev;
>> +	struct regmap *regmap;
>> +	struct device **active_pds;
>> +	u32 pds_num;
>> +	u32 active_pd_count;
>> +	struct genpd_onecell_data onecell_data;
>> +	const struct imx_blk_ctl_dev_data *dev_data;
>> +	struct clk_bulk_data *clks;
>> +	u32 num_clks;
>> +
>> +	atomic_t power_count;
>> +};
>> +
>> +#define IMX_BLK_CTL(_type, _name, _parent_name, _id, _offset, _mask, _rst_offset, _rst_mask,	\
>> +		    _flags)								\
>> +	{										\
>> +		.type = _type,								\
>> +		.name = _name,								\
>> +		.parent_name = _parent_name,						\
>> +		.id = _id,								\
>> +		.offset = _offset,							\
>> +		.mask = _mask,								\
>> +		.flags = _flags,							\
>> +		.rst_offset = _rst_offset,						\
>> +		.rst_mask = _rst_mask,							\
>> +	}
>> +
>> +#define IMX_BLK_CTL_PD(_name, _parent_name, _id, _offset, _mask, _rst_offset, _rst_mask, _flags) \
>> +	IMX_BLK_CTL(BLK_CTL_PD, _name, _parent_name, _id, _offset, _mask, _rst_offset,		\
>> +		    _rst_mask, _flags)
>> +
>> +int imx_blk_ctl_register(struct device *dev);
>> +
>> +#define IMX_BLK_CTL_PD_HANDSHAKE	BIT(0)
>> +#define IMX_BLK_CTL_PD_RESET		BIT(1)
>> +#define IMX_BLK_CTL_PD_BUS		BIT(2)
>> +
>> +const extern struct dev_pm_ops imx_blk_ctl_pm_ops;
>> +
>> +#endif
> 
>