Re: [PATCH 2/2] hwspinlock: add SUNXI implementation

Bjorn Andersson
2020-11-21T04:01:30Z

On Thu 19 Nov 00:44 CST 2020, fuyao@allwinnertech.com wrote:

> From: fuyao <fuyao@allwinnertech.com>
>
> Add hwspinlock support for the SUNXI Hardware Spinlock device.
>
> The Hardware Spinlock device on SUNXI provides hardware assistance
> for synchronization between the multiple processors in the system
> (Cortex-A7, or1k, Xtensa DSP, Cortex-A53)
>
> Signed-off-by: fuyao <fuyao@allwinnertech.com>
> ---
> MAINTAINERS | 6 +
> drivers/hwspinlock/Kconfig | 10 ++
> drivers/hwspinlock/Makefile | 1 +
> drivers/hwspinlock/sunxi_hwspinlock.c | 205 ++++++++++++++++++++++++++
> 4 files changed, 222 insertions(+)
> create mode 100644 drivers/hwspinlock/sunxi_hwspinlock.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e451dcce054f0..68d25574432d0 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -737,6 +737,12 @@ L: linux-media@vger.kernel.org
> S: Maintained
> F: drivers/staging/media/sunxi/cedrus/
>
> +ALLWINNER HWSPINLOCK DRIVER
> +M: fuyao <fuyao@allwinnertech.com>
> +S: Maintained
> +F: drivers/hwspinlock/sunxi_hwspinlock.c
> +F: Documentation/devicetree/bindings/hwlock/sunxi,hwspinlock.yaml
> +
> ALPHA PORT
> M: Richard Henderson <rth@twiddle.net>
> M: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
> diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
> index 32cd26352f381..4d0d516dcb544 100644
> --- a/drivers/hwspinlock/Kconfig
> +++ b/drivers/hwspinlock/Kconfig
> @@ -55,6 +55,16 @@ config HWSPINLOCK_STM32
>
> If unsure, say N.
>
> +config HWSPINLOCK_SUNXI
> + tristate "SUNXI Hardware Spinlock device"
> + depends on ARCH_SUNXI || COMPILE_TEST
> + help
> + Say y here to support the SUNXI Hardware Semaphore functionality, which
> + provides a synchronisation mechanism for the various processor on the
> + SoC.
> +
> + 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 ed053e3f02be4..839a053205f73 100644
> --- a/drivers/hwspinlock/Makefile
> +++ b/drivers/hwspinlock/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_HWSPINLOCK_SIRF) += sirf_hwspinlock.o
> obj-$(CONFIG_HWSPINLOCK_SPRD) += sprd_hwspinlock.o
> obj-$(CONFIG_HWSPINLOCK_STM32) += stm32_hwspinlock.o
> obj-$(CONFIG_HSEM_U8500) += u8500_hsem.o
> +obj-$(CONFIG_HWSPINLOCK_SUNXI) += sunxi_hwspinlock.o
> diff --git a/drivers/hwspinlock/sunxi_hwspinlock.c b/drivers/hwspinlock/sunxi_hwspinlock.c
> new file mode 100644
> index 0000000000000..2c3dc148c9b72
> --- /dev/null
> +++ b/drivers/hwspinlock/sunxi_hwspinlock.c
> @@ -0,0 +1,205 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * SUNXI hardware spinlock driver
> + *
> + * Copyright (C) 2020 Allwinnertech - http://www.allwinnertech.com
> + *

Please remove the remainder of this comment, it's already covered by the
SPDX header above.

> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/bitops.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/hwspinlock.h>
> +#include <linux/clk.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_device.h>
> +#include <linux/err.h>
> +#include <linux/reset.h>

You don't need all of these.

> +
> +#include "hwspinlock_internal.h"
> +
> +/* hardware spinlock register list */
> +#define LOCK_SYS_STATUS_REG (0x0000)
> +#define LOCK_STATUS_REG (0x0010)
> +#define LOCK_BASE_OFFSET (0x0100)
> +#define LOCK_BASE_ID (0)

No need for the parenthesis on these, please drop them.

> +
> +/* Possible values of SPINLOCK_LOCK_REG */
> +#define SPINLOCK_NOTTAKEN (0) /* free */
> +#define SPINLOCK_TAKEN (1) /* locked */
> +
> +struct sunxi_spinlock_config {
> + int nspin;
> +};
> +
> +static int sunxi_hwspinlock_trylock(struct hwspinlock *lock)
> +{
> + void __iomem *lock_addr = lock->priv;
> +
> + /* attempt to acquire the lock by reading its value */
> + return (readl(lock_addr) == SPINLOCK_NOTTAKEN);

Please drop the outer ().

> +}
> +
> +static void sunxi_hwspinlock_unlock(struct hwspinlock *lock)
> +{
> + void __iomem *lock_addr = lock->priv;
> +
> + /* release the lock by writing 0 to it */
> + writel(SPINLOCK_NOTTAKEN, lock_addr);
> +}
> +
> +/*
> + * relax the SUNXI interconnect while spinning on it.
> + *
> + * The specs recommended that the retry delay time will be
> + * just over half of the time that a requester would be
> + * expected to hold the lock.
> + *
> + * in sunxi spinlock time less then 200 cycles
> + *
> + * The number below is taken from an hardware specs example,
> + * obviously it is somewhat arbitrary.

Thank you for the good explanation.

> + */
> +static void sunxi_hwspinlock_relax(struct hwspinlock *lock)
> +{
> + ndelay(50);
> +}
> +
> +static const struct hwspinlock_ops sunxi_hwspinlock_ops = {
> + .trylock = sunxi_hwspinlock_trylock,
> + .unlock = sunxi_hwspinlock_unlock,
> + .relax = sunxi_hwspinlock_relax,
> +};
> +
> +struct sunxi_hwspinlock_device {
> + struct hwspinlock_device *bank;
> + struct clk *bus_clk;
> + struct reset_control *reset;
> +};
> +
> +static void sunxi_hwspinlock_clk_init(struct platform_device *pdev,
> + struct sunxi_hwspinlock_device *private)
> +{
> + private->bus_clk = devm_clk_get(&pdev->dev, NULL);
> + private->reset = devm_reset_control_get(&pdev->dev, NULL);

You should check the return value of these, e.g. for EPROBE_DEFER and if
so return appropriately from sunxi_hwspinlock_probe().

So please move them to the probe function to make this easier and
cleaner.

> +
> + if (private->reset)
> + reset_control_deassert(private->reset);
> + if (private->bus_clk)
> + clk_prepare_enable(private->bus_clk);

Both of these apis start with

if (!argument)
return;

So there's no need for you to check for NULL before calling them. Also
to make it clear that you want these to be deassered and prepare_enabled
between probe and remvoe, move them into probe (and next function into
remove).

> +}
> +
> +static void sunxi_hwspinlock_clk_dinit(struct sunxi_hwspinlock_device *private)
> +{
> + if (private->reset)
> + reset_control_assert(private->reset);
> + if (private->bus_clk)
> + clk_disable(private->bus_clk);
> +}
> +
> +static const struct sunxi_spinlock_config spin_ver_1 = {
> + .nspin = 32,
> +};
> +
> +static const struct of_device_id sunxi_hwspinlock_of_match[] = {
> + {
> + .compatible = "allwinner,h3-hwspinlock",
> + .data = &spin_ver_1,

If all cases comes with the same "data", then please just put nspin in a
#define until you're going to support hardware that has some other
number of locks.

> + },
> + {
> + .compatible = "allwinner,h6-hwspinlock",
> + .data = &spin_ver_1,
> + },
> + { /* Sentinel */ },

No need to spell out "/* Sentinel */", leave it emtpy and please drop the , at
the end.

> +};
> +MODULE_DEVICE_TABLE(of, sunxi_hwspinlock_of_match);

Please move this down by sunxi_hwspinlock_driver and use
device_get_match_data() instead of of_match_device().

> +
> +static int sunxi_hwspinlock_probe(struct platform_device *pdev)
> +{
> + struct sunxi_hwspinlock_device *private;
> + struct hwspinlock_device *bank;
> + struct hwspinlock *hwlock;
> + const struct sunxi_spinlock_config *config;
> + const struct of_device_id *match;
> + void __iomem *iobase;
> + int num_locks, i, ret;
> +
> + iobase = devm_platform_ioremap_resource(pdev, 0);
> + if (PTR_ERR(iobase))
> + return PTR_ERR(iobase);
> +
> + match = of_match_device(of_match_ptr(sunxi_hwspinlock_of_match),
> + &pdev->dev);
> + if (!match)
> + return -ENODEV;
> +
> + config = match->data;
> + num_locks = config->nspin;
> +
> + private = devm_kzalloc(&pdev->dev, sizeof(*private), GFP_KERNEL);
> + if (!private)
> + return -ENOMEM;
> +
> + bank = devm_kzalloc(&pdev->dev,
> + sizeof(*bank) + num_locks * sizeof(*hwlock),
> + GFP_KERNEL);
> + if (!bank)
> + return -ENOMEM;
> +
> + private->bank = bank;
> + sunxi_hwspinlock_clk_init(pdev, private);
> +
> + platform_set_drvdata(pdev, private);
> +
> + for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
> + hwlock->priv = iobase + LOCK_BASE_OFFSET + sizeof(u32) * i;
> +
> + ret = devm_hwspin_lock_register(&pdev->dev, bank, &sunxi_hwspinlock_ops,
> + LOCK_BASE_ID, num_locks);

This returns 0 or -errno, so rather than returning ret if ret otherwise
0, just do:

return devm_hwspin_lock_register(...)

> + if (ret)
> + return ret;
> +
> +
> + return 0;
> +}
> +
> +static int sunxi_hwspinlock_remove(struct platform_device *pdev)
> +{
> + struct sunxi_hwspinlock_device *private = platform_get_drvdata(pdev);
> +
> + sunxi_hwspinlock_clk_dinit(private);
> +
> + return 0;
> +}
> +
> +static struct platform_driver sunxi_hwspinlock_driver = {
> + .probe = sunxi_hwspinlock_probe,
> + .remove = sunxi_hwspinlock_remove,
> + .driver = {
> + .name = "sunxi-hwspinlock",
> + .owner = THIS_MODULE,

module_platform_driver() fills out .owner for you, so please remove
this.

> + .of_match_table = of_match_ptr(sunxi_hwspinlock_of_match),

Please skip of_match_ptr(), it will just cause build warnings when
compile tested without CONFIG_OF.

Thank you,
Bjorn

> + },
> +};
> +
> +module_platform_driver(sunxi_hwspinlock_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Hardware spinlock driver for SUNXI");
> +MODULE_AUTHOR("fuyao <fuyao@allwinnertech.com>");
> --
> 2.29.2
>