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SubjectRe: [PATCH 2/2] hwspinlock: add sunxi hardware spinlock support
On Wed 18 Nov 04:02 CST 2020, Wilken Gottwalt wrote:

> Adds the sunxi_hwspinlock driver and updates makefiles/maintainers.
>
> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
> ---
> MAINTAINERS | 6 +
> drivers/hwspinlock/Kconfig | 9 +
> drivers/hwspinlock/Makefile | 1 +
> drivers/hwspinlock/sunxi_hwspinlock.c | 282 ++++++++++++++++++++++++++
> 4 files changed, 298 insertions(+)
> create mode 100644 drivers/hwspinlock/sunxi_hwspinlock.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5cc595ac7b28..7765da172f10 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/sunxi-hwspinlock.yaml
> +F: drivers/hwspinlock/sunxi_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..27b6e22126f7 100644
> --- a/drivers/hwspinlock/Kconfig
> +++ b/drivers/hwspinlock/Kconfig
> @@ -55,6 +55,15 @@ 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 Allwinner hardware mutex device available
> + in the H2+, H3, H5 and H6 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..bf46bee95226 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-$(CONFIG_HWSPINLOCK_SUNXI) += sunxi_hwspinlock.o
> obj-$(CONFIG_HSEM_U8500) += u8500_hsem.o
> diff --git a/drivers/hwspinlock/sunxi_hwspinlock.c b/drivers/hwspinlock/sunxi_hwspinlock.c
> new file mode 100644
> index 000000000000..54e6ad3ac1c2
> --- /dev/null
> +++ b/drivers/hwspinlock/sunxi_hwspinlock.c
> @@ -0,0 +1,282 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * sunxi_hwspinlock.c - hardware spinlock driver for Allwinner SoCs
> + * Copyright (C) 2020 Wilken Gottwalt <wilken.gottwalt@posteo.net>
> + */
> +
> +#include <linux/bitops.h>
> +#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 "sunxi_hwspinlock"
> +
> +#define SPINLOCK_BASE_ID 0 /* there is only one hwspinlock device in each SoC */
> +#define SPINLOCK_SYSSTATUS_REG 0x0000
> +#define SPINLOCK_STATUS_REG 0x0010
> +#define SPINLOCK_LOCK_REGN 0x0100
> +#define SPINLOCK_NOTTAKEN 0
> +#define SPINLOCK_TAKEN 1
> +
> +struct sunxi_hwspinlock {
> + void __iomem *io_base;
> +};
> +
> +struct sunxi_hwspinlock_data {
> + void __iomem *io_base;
> + struct hwspinlock_device *bank;
> + struct reset_control *reset;
> + struct clk *ahb_clock;
> + struct dentry *debugfs;
> + int nlocks;
> +};
> +
> +#ifdef CONFIG_DEBUG_FS
> +
> +static int hwlocks_supported_show(struct seq_file *seqf, void *unused)
> +{
> + struct sunxi_hwspinlock_data *priv = seqf->private;
> +
> + seq_printf(seqf, "%d\n", priv->nlocks);
> +
> + return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(hwlocks_supported);
> +
> +static int hwlocks_inuse_show(struct seq_file *seqf, void *unused)
> +{
> + struct sunxi_hwspinlock_data *priv = seqf->private;
> + int inuse;
> +
> + /* getting the status of only the main 32 spinlocks is supported */
> + inuse = hweight32(readl(priv->io_base + SPINLOCK_STATUS_REG));

So this returns how many of the locks are taken? How is that useful?

> + seq_printf(seqf, "%d\n", inuse);
> +
> + return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(hwlocks_inuse);
> +
> +static void sunxi_hwspinlock_debugfs_init(struct sunxi_hwspinlock_data *priv)
> +{
> + char name[32];
> +
> + scnprintf(name, sizeof(name), "%s", DRIVER_NAME);

Why not just pass DRIVER_NAME directly to debugfs_create_dir()?

> +
> + priv->debugfs = debugfs_create_dir(name, NULL);
> + debugfs_create_file("hwlocks_supported", 0444, priv->debugfs, priv,
> + &hwlocks_supported_fops);
> + debugfs_create_file("hwlocks_inuse", 0444, priv->debugfs, priv, &hwlocks_inuse_fops);
> +}
> +
> +#else
> +
> +static void sunxi_hwspinlock_debugfs_init(struct sunxi_hwspinlock_data *priv)
> +{
> +}
> +
> +#endif
> +
> +static int sunxi_hwspinlock_trylock(struct hwspinlock *lock)
> +{
> + struct sunxi_hwspinlock_data *priv = lock->priv;
> + void __iomem *lock_addr = priv->io_base;
> +
> + return (readl(lock_addr) == SPINLOCK_NOTTAKEN);
> +}
> +
> +static void sunxi_hwspinlock_unlock(struct hwspinlock *lock)
> +{
> + struct sunxi_hwspinlock_data *priv = lock->priv;
> + void __iomem *lock_addr = priv->io_base;
> +
> + writel(SPINLOCK_NOTTAKEN, lock_addr);
> +}
> +
> +static const struct hwspinlock_ops sunxi_hwspinlock_ops = {
> + .trylock = sunxi_hwspinlock_trylock,
> + .unlock = sunxi_hwspinlock_unlock,
> +};
> +
> +static int sunxi_hwspinlock_probe(struct platform_device *pdev)
> +{
> + struct device_node *node = pdev->dev.of_node;

I don't see a need for this, or the check to fail if it's NULL. Please
remove it.

> + struct sunxi_hwspinlock_data *priv;
> + struct sunxi_hwspinlock *hwpriv;
> + struct hwspinlock *hwlock;
> + struct resource *res;
> + int num_banks, err, i;
> +
> + if (!node)
> + return -ENODEV;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -ENODEV;
> +
> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->io_base = devm_ioremap_resource(&pdev->dev, res);

Please use devm_platform_ioremap_resource() instead.

> + if (IS_ERR(priv->io_base)) {
> + err = PTR_ERR(priv->io_base);
> + dev_err(&pdev->dev, "unable to request MMIO (%d)\n", err);
> + return err;
> + }
> +
> + priv->ahb_clock = devm_clk_get(&pdev->dev, "ahb");
> + if (IS_ERR(priv->ahb_clock)) {
> + err = PTR_ERR(priv->ahb_clock);
> + dev_err(&pdev->dev, "unable to get AHB clock (%d)\n", err);
> + return err;
> + }
> +
> + priv->reset = devm_reset_control_get_optional(&pdev->dev, "ahb");
> + if (IS_ERR(priv->reset)) { > + err = PTR_ERR(priv->reset);
> + if (err == -EPROBE_DEFER)
> + return err;
> +
> + dev_info(&pdev->dev, "no optional reset control available (%d)\n", err);

In the even that no "ahb" reset is specified priv->reset is NULL, as
such if you get here there's something wrong - so it's better to fail
here.

And you can use the convenient dev_err_probe() function to deal with the
EPROBE_DEFER.

> + priv->reset = NULL;
> + }
> +
> + if (priv->reset) {

It's perfectly fine to call reset_control_deassert(NULL); so you can
omit this check.

> + 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_clock);
> + if (err) {
> + dev_err(&pdev->dev, "unable to prepare AHB clock (%d)\n", err);
> + goto reset_fail;
> + }
> +
> + /* bit 28 and 29 hold the amount of spinlock banks */
> + num_banks = (readl(priv->io_base + SPINLOCK_SYSSTATUS_REG) >> 28) & 0x03;
> + switch (num_banks) {
> + case 1 ... 4:

But the comment above says...and num_banks was & 0x3, so how can it be ...4?

> + /*
> + * 32, 64, 128 and 256 spinlocks are supported by the hardware implementation,
> + * though most only support 32 spinlocks
> + */
> + priv->nlocks = 1 << (4 + num_banks);
> + break;
> + default:

Given the mask above I believe this would only happen if bits 28 and 29
are both 0...

Regardless I think that this would be better written as a

if (num_banks == invalid) {
...
goto fail;
}

priv->nlocks = ...;

> + dev_err(&pdev->dev, "unsupported hwspinlock setup (%d)\n", num_banks);
> + err = -EINVAL;
> + goto fail;
> + }
> +
> + /*
> + * the Allwinner hwspinlock device uses 32bit registers for representing every single
> + * spinlock, which is a real waste of space
> + */

Might be a waste, but having them be the natural write size in hardware
makes sense. I'm however not sure what this comment has to do with the
following allocation.

> + priv->bank = devm_kzalloc(&pdev->dev, priv->nlocks * sizeof(*hwlock) + sizeof(*priv->bank),

Consider using struct_size() here.

> + GFP_KERNEL);
> + if (!priv->bank) {
> + err = -ENOMEM;
> + goto fail;

If you do this allocation before you start the clock and deassert the
reset you can just return -ENOMEM here, instead of the goto.

> + }
> +
> + for (i = 0, hwlock = &priv->bank->lock[0]; i < priv->nlocks; ++i, ++hwlock) {
> + hwlock->priv = devm_kzalloc(&pdev->dev, sizeof(struct sunxi_hwspinlock),
> + GFP_KERNEL);

hwpriv = devm_kzalloc(&pdev->dev, sizeof(*hwpriv), GFP_KERNEL);
if (!hwpriv)
return -ENOMEM;

hwpriv->io_base = ...;
priv->bank->lock[i].priv = hwpriv;


> + if (!hwlock->priv) {
> + err = -ENOMEM;
> + goto fail;
> + }
> +
> + hwpriv = hwlock->priv;
> + hwpriv->io_base = priv->io_base + SPINLOCK_LOCK_REGN + sizeof(u32) * i;
> + }
> +
> + err = hwspin_lock_register(priv->bank, &pdev->dev, &sunxi_hwspinlock_ops, SPINLOCK_BASE_ID,
> + priv->nlocks);
> + if (err) {
> + dev_err(&pdev->dev, "unable to register hwspinlocks (%d)\n", err);
> + goto fail;
> + }
> +
> + sunxi_hwspinlock_debugfs_init(priv);
> +
> + dev_dbg(&pdev->dev, "SUNXI hardware spinlock driver enabled (%d locks)\n", priv->nlocks);
> +
> + return 0;
> +
> +fail:
> + clk_disable_unprepare(priv->ahb_clock);
> +
> +reset_fail:
> + if (priv->reset)
> + reset_control_assert(priv->reset);
> +
> + return err;
> +}
> +
> +static int sunxi_hwspinlock_remove(struct platform_device *pdev)
> +{
> + struct sunxi_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;
> + }
> +
> + if (priv->reset)
> + reset_control_assert(priv->reset);
> +
> + clk_disable_unprepare(priv->ahb_clock);

By using devm_add_action_or_reset() to set up an "assert and unprepare"-
function you can use devm_hwspin_lock_register(), you can drop the
remove function and you can clean up your sunxi_hwspinlock_data (e.g.
you no longer need a pointer to priv->bank).

> +
> + return 0;
> +}
> +
> +static const struct of_device_id sunxi_hwspinlock_ids[] = {
> + { .compatible = "allwinner,sun8i-hwspinlock", },
> + { .compatible = "allwinner,sun50i-hwspinlock", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sunxi_hwspinlock_ids);
> +
> +static struct platform_driver sunxi_hwspinlock_driver = {
> + .probe = sunxi_hwspinlock_probe,
> + .remove = sunxi_hwspinlock_remove,
> + .driver = {
> + .name = DRIVER_NAME,
> + .of_match_table = of_match_ptr(sunxi_hwspinlock_ids),

Please avoid of_match_ptr, as this will cause warnings about unused
variables when COMPILE_TEST without OF.

Regards,
Bjorn

> + },
> +};
> +
> +static int __init sunxi_hwspinlock_init(void)
> +{
> + return platform_driver_register(&sunxi_hwspinlock_driver);
> +}
> +postcore_initcall(sunxi_hwspinlock_init);
> +
> +static void __exit sunxi_hwspinlock_exit(void)
> +{
> + platform_driver_unregister(&sunxi_hwspinlock_driver);
> +}
> +module_exit(sunxi_hwspinlock_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("SUNXI hardware spinlock driver");
> +MODULE_AUTHOR("Wilken Gottwalt <wilken.gottwalt@posteo.net>");
> --
> 2.29.2
>

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