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

fuyao
2020-11-21T14:35:06Z

On Fri, Nov 20, 2020 at 10:01:04PM -0600, Bjorn Andersson wrote:
> 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>");

Thanks for you review, I read it carefully, and learned a lot.

Maxim tells that there is already the same submission, so this
submission will be abandoned.

thanks again.

--
fuyao