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Date:   Thu, 7 Jan 2021 11:43:48 -0600
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Wilken Gottwalt <wilken.gottwalt@posteo.net>
Cc:     linux-kernel@vger.kernel.org, Ohad Ben-Cohen <ohad@wizery.com>,
        Baolin Wang <baolin.wang7@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@siol.net>
Subject: Re: [PATCH v5 2/2] hwspinlock: add sun6i hardware spinlock support
Message-ID: <X/dIVIvjJh6olPYx@builder.lan>
References: <cover.1608721968.git.wilken.gottwalt@posteo.net>
 <0deae76aec31586da45c316546b12bcc316442ee.1608721968.git.wilken.gottwalt@posteo.net>
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On Wed 23 Dec 05:35 CST 2020, Wilken Gottwalt wrote:

> Adds the sun6i_hwspinlock driver for the hardware spinlock unit found in
> most of the sun6i compatible SoCs.
> 
> This unit provides at least 32 spinlocks in hardware. The implementation
> supports 32, 64, 128 or 256 32bit registers. A lock can be taken by
> reading a register and released by writing a 0 to it. This driver
> supports all 4 spinlock setups, but for now only the first setup (32
> locks) seem to exist in available devices. This spinlock unit is shared
> between all ARM cores and the embedded companion core. All of them can
> take/release a lock with a single cycle operation. It can be used to
> sync access to devices shared by the ARM cores and the companion core.
> 
> There are two ways to check if a lock is taken. The first way is to read
> a lock. If a 0 is returned, the lock was free and is taken now. If an 1
> is returned, the caller has to try again. Which means the lock is taken.
> The second way is to read a 32bit wide status register where every bit
> represents one of the 32 first locks. According to the datasheets this
> status register supports only the 32 first locks. This is the reason the
> first way (lock read/write) approach is used to be able to cover all 256
> locks in future devices. The driver also reports the amount of supported
> locks via debugfs.
> 
> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
> ---
> Changes in v5:
>   - changed symbols to the earliest known supported SoC (sun6i/a31)
>   - changed init back to classic probe/remove callbacks
> 
> Changes in v4:
>   - further simplified driver
>   - fixed an add_action_and_reset_ function issue
>   - changed bindings from sun8i-hwspinlock to sun8i-a33-hwspinlock
> 
> Changes in v3:
>   - moved test description to cover letter
>   - changed name and symbols from sunxi to sun8i
>   - improved driver description
>   - further simplified driver
>   - fully switched to devm_* and devm_add_action_* functions
> 
> Changes in v2:
>   - added suggestions from Bjorn Andersson and Maxime Ripard
>   - provided better driver and test description
> ---
>  MAINTAINERS                           |   6 +
>  drivers/hwspinlock/Kconfig            |   9 ++
>  drivers/hwspinlock/Makefile           |   1 +
>  drivers/hwspinlock/sun6i_hwspinlock.c | 214 ++++++++++++++++++++++++++
>  4 files changed, 230 insertions(+)
>  create mode 100644 drivers/hwspinlock/sun6i_hwspinlock.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ad0e34bf8453..0842b2a3ea89 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -722,6 +722,12 @@ L:	linux-crypto@vger.kernel.org
>  S:	Maintained
>  F:	drivers/crypto/allwinner/
>  
> +ALLWINNER HARDWARE SPINLOCK SUPPORT
> +M:	Wilken Gottwalt <wilken.gottwalt@posteo.net>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/hwlock/sun6i-a31-hwspinlock.yaml
> +F:	drivers/hwspinlock/sun6i_hwspinlock.c
> +
>  ALLWINNER THERMAL DRIVER
>  M:	Vasily Khoruzhick <anarsoul@gmail.com>
>  M:	Yangtao Li <tiny.windzz@gmail.com>
> diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
> index 32cd26352f38..56ecc1aa3166 100644
> --- a/drivers/hwspinlock/Kconfig
> +++ b/drivers/hwspinlock/Kconfig
> @@ -55,6 +55,15 @@ config HWSPINLOCK_STM32
>  
>  	  If unsure, say N.
>  
> +config HWSPINLOCK_SUN6I
> +	tristate "SUN6I Hardware Spinlock device"
> +	depends on ARCH_SUNXI || COMPILE_TEST
> +	help
> +	  Say y here to support the SUN6I Hardware Spinlock device which can be
> +	  found in most of the sun6i compatible Allwinner SoCs.
> +
> +	  If unsure, say N.
> +
>  config HSEM_U8500
>  	tristate "STE Hardware Semaphore functionality"
>  	depends on ARCH_U8500 || COMPILE_TEST
> diff --git a/drivers/hwspinlock/Makefile b/drivers/hwspinlock/Makefile
> index ed053e3f02be..83ec4f03decc 100644
> --- a/drivers/hwspinlock/Makefile
> +++ b/drivers/hwspinlock/Makefile
> @@ -9,4 +9,5 @@ obj-$(CONFIG_HWSPINLOCK_QCOM)		+= qcom_hwspinlock.o
>  obj-$(CONFIG_HWSPINLOCK_SIRF)		+= sirf_hwspinlock.o
>  obj-$(CONFIG_HWSPINLOCK_SPRD)		+= sprd_hwspinlock.o
>  obj-$(CONFIG_HWSPINLOCK_STM32)		+= stm32_hwspinlock.o
> +obj-$(CONFIG_HWSPINLOCK_SUN6I)		+= sun6i_hwspinlock.o
>  obj-$(CONFIG_HSEM_U8500)		+= u8500_hsem.o
> diff --git a/drivers/hwspinlock/sun6i_hwspinlock.c b/drivers/hwspinlock/sun6i_hwspinlock.c
> new file mode 100644
> index 000000000000..ba56eed818e7
> --- /dev/null
> +++ b/drivers/hwspinlock/sun6i_hwspinlock.c
> @@ -0,0 +1,214 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * sun6i_hwspinlock.c - hardware spinlock driver for sun6i compatible Allwinner SoCs
> + * Copyright (C) 2020 Wilken Gottwalt <wilken.gottwalt@posteo.net>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/debugfs.h>
> +#include <linux/errno.h>
> +#include <linux/hwspinlock.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/types.h>
> +
> +#include "hwspinlock_internal.h"
> +
> +#define DRIVER_NAME		"sun6i_hwspinlock"

Isn't this the same as KBUILD_MODNAME?

> +
> +#define SPINLOCK_BASE_ID	0 /* there is only one hwspinlock device per SoC */
> +#define SPINLOCK_SYSSTATUS_REG	0x0000
> +#define SPINLOCK_LOCK_REGN	0x0100
> +#define SPINLOCK_NOTTAKEN	0
> +
> +struct sun6i_hwspinlock_data {
> +	struct hwspinlock_device *bank;
> +	struct reset_control *reset;
> +	struct clk *ahb_clk;
> +	struct dentry *debugfs;
> +	int nlocks;
> +};
> +
> +#ifdef CONFIG_DEBUG_FS
> +
> +static int hwlocks_supported_show(struct seq_file *seqf, void *unused)
> +{
> +	struct sun6i_hwspinlock_data *priv = seqf->private;
> +
> +	seq_printf(seqf, "%d\n", priv->nlocks);
> +
> +	return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(hwlocks_supported);
> +
> +static void sun6i_hwspinlock_debugfs_init(struct sun6i_hwspinlock_data *priv)
> +{
> +	priv->debugfs = debugfs_create_dir(DRIVER_NAME, NULL);
> +	debugfs_create_file("supported", 0444, priv->debugfs, priv, &hwlocks_supported_fops);
> +}
> +
> +#else
> +
> +static void sun6i_hwspinlock_debugfs_init(struct sun6i_hwspinlock_data *priv)
> +{
> +}
> +
> +#endif
> +
> +static int sun6i_hwspinlock_trylock(struct hwspinlock *lock)
> +{
> +	void __iomem *lock_addr = lock->priv;
> +
> +	return (readl(lock_addr) == SPINLOCK_NOTTAKEN);
> +}
> +
> +static void sun6i_hwspinlock_unlock(struct hwspinlock *lock)
> +{
> +	void __iomem *lock_addr = lock->priv;
> +
> +	writel(SPINLOCK_NOTTAKEN, lock_addr);
> +}
> +
> +static const struct hwspinlock_ops sun6i_hwspinlock_ops = {
> +	.trylock	= sun6i_hwspinlock_trylock,
> +	.unlock		= sun6i_hwspinlock_unlock,
> +};
> +
> +static int sun6i_hwspinlock_probe(struct platform_device *pdev)
> +{
> +	struct sun6i_hwspinlock_data *priv;
> +	struct hwspinlock *hwlock;
> +	void __iomem *io_base;
> +	u32 num_banks;
> +	int err, i;
> +
> +	io_base = devm_platform_ioremap_resource(pdev, SPINLOCK_BASE_ID);
> +	if (IS_ERR(io_base))
> +		return PTR_ERR(io_base);
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->ahb_clk = devm_clk_get(&pdev->dev, "ahb");
> +	if (IS_ERR(priv->ahb_clk)) {
> +		err = PTR_ERR(priv->ahb_clk);
> +		dev_err(&pdev->dev, "unable to get AHB clock (%d)\n", err);
> +		return err;
> +	}
> +
> +	priv->reset = devm_reset_control_get(&pdev->dev, "ahb");
> +	if (IS_ERR(priv->reset))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(priv->reset),
> +				     "unable to get reset control\n");
> +
> +	err = reset_control_deassert(priv->reset);
> +	if (err) {
> +		dev_err(&pdev->dev, "deassert reset control failure (%d)\n", err);
> +		return err;
> +	}
> +
> +	err = clk_prepare_enable(priv->ahb_clk);
> +	if (err) {
> +		dev_err(&pdev->dev, "unable to prepare AHB clk (%d)\n", err);
> +		goto clk_fail;
> +	}
> +
> +	/*
> +	 * bit 28 and 29 represents the hwspinlock setup
> +	 *
> +	 * every datasheet (A64, A80, A83T, H3, H5, H6 ...) says the default value is 0x1 and 0x1
> +	 * to 0x4 represent 32, 64, 128 and 256 locks
> +	 * but later datasheets (H5, H6) say 00, 01, 10, 11 represent 32, 64, 128 and 256 locks,
> +	 * but that would mean H5 and H6 have 64 locks, while their datasheets talk about 32 locks
> +	 * all the time, not a single mentioning of 64 locks
> +	 * the 0x4 value is also not representable by 2 bits alone, so some datasheets are not
> +	 * correct
> +	 * one thing have all in common, default value of the sysstatus register is 0x10000000,
> +	 * which results in bit 28 being set
> +	 * this is the reason 0x1 is considered being 32 locks and bit 30 is taken into account
> +	 * verified on H2+ (datasheet 0x1 = 32 locks) and H5 (datasheet 01 = 64 locks)
> +	 */
> +	num_banks = readl(io_base + SPINLOCK_SYSSTATUS_REG) >> 28;
> +	switch (num_banks) {
> +	case 1 ... 4:
> +		priv->nlocks = 1 << (4 + num_banks);
> +		break;
> +	default:
> +		err = -EINVAL;
> +		dev_err(&pdev->dev, "unsupported hwspinlock setup (%d)\n", num_banks);
> +		goto bank_fail;
> +	}
> +
> +	priv->bank = devm_kzalloc(&pdev->dev, struct_size(priv->bank, lock, priv->nlocks),
> +				  GFP_KERNEL);
> +	if (!priv->bank) {
> +		err = -ENOMEM;
> +		goto bank_fail;
> +	}
> +
> +	for (i = 0; i < priv->nlocks; ++i) {
> +		hwlock = &priv->bank->lock[i];
> +		hwlock->priv = io_base + SPINLOCK_LOCK_REGN + sizeof(u32) * i;
> +	}
> +
> +	/* failure of debugfs is considered non-fatal */
> +	sun6i_hwspinlock_debugfs_init(priv);
> +	if (IS_ERR(priv->debugfs))
> +		priv->debugfs = NULL;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	return devm_hwspin_lock_register(&pdev->dev, priv->bank, &sun6i_hwspinlock_ops,
> +					 SPINLOCK_BASE_ID, priv->nlocks);

If this fails you will leave the reset deasserted and the clocks
prepared. So please handle this as well.

Regards,
Bjorn

> +bank_fail:
> +	clk_disable_unprepare(priv->ahb_clk);
> +clk_fail:
> +	reset_control_assert(priv->reset);
> +
> +	return err;
> +}
> +
> +static int sun6i_hwspinlock_remove(struct platform_device *pdev)
> +{
> +	struct sun6i_hwspinlock_data *priv = platform_get_drvdata(pdev);
> +	int err;
> +
> +	debugfs_remove_recursive(priv->debugfs);
> +
> +	err = hwspin_lock_unregister(priv->bank);
> +	if (err) {
> +		dev_err(&pdev->dev, "unregister device failed (%d)\n", err);
> +		return err;
> +	}
> +
> +	clk_disable_unprepare(priv->ahb_clk);
> +	reset_control_assert(priv->reset);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id sun6i_hwspinlock_ids[] = {
> +	{ .compatible = "allwinner,sun6i-a31-hwspinlock", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, sun6i_hwspinlock_ids);
> +
> +static struct platform_driver sun6i_hwspinlock_driver = {
> +	.probe	= sun6i_hwspinlock_probe,
> +	.remove	= sun6i_hwspinlock_remove,
> +	.driver	= {
> +		.name		= DRIVER_NAME,
> +		.of_match_table	= sun6i_hwspinlock_ids,
> +	},
> +};
> +module_platform_driver(sun6i_hwspinlock_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("SUN6I hardware spinlock driver");
> +MODULE_AUTHOR("Wilken Gottwalt <wilken.gottwalt@posteo.net>");
> -- 
> 2.29.2
>