Message-ID: <20201121143306.GB23438@debian>
Date:   Sat, 21 Nov 2020 22:33:06 +0800
From:   fuyao <fuyao@...winnertech.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     mripard@...nel.org, wens@...e.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hwspinlock: add SUNXI implementation

On Fri, Nov 20, 2020 at 10:01:04PM -0600, Bjorn Andersson wrote:
> On Thu 19 Nov 00:44 CST 2020, fuyao@...winnertech.com wrote:
> 
> > From: fuyao <fuyao@...winnertech.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@...winnertech.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@...r.kernel.org
> >  S:	Maintained
> >  F:	drivers/staging/media/sunxi/cedrus/
> >  
> > +ALLWINNER HWSPINLOCK DRIVER
> > +M:	fuyao <fuyao@...winnertech.com>
> > +S:	Maintained
> > +F:	drivers/hwspinlock/sunxi_hwspinlock.c
> > +F:      Documentation/devicetree/bindings/hwlock/sunxi,hwspinlock.yaml
> > +
> >  ALPHA PORT
> >  M:	Richard Henderson <rth@...ddle.net>
> >  M:	Ivan Kokshaysky <ink@...assic.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@...winnertech.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

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