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Date: Wed, 6 May 2015 11:13:43 -0700
From: Bjorn Andersson <bjorn@...o.se>
To: Barry Song <21cnbao@...il.com>
Cc: Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Ohad Ben-Cohen <ohad@...ery.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Wei Chen <wei.chen@....com>, Barry Song <Baohua.Song@....com>
Subject: Re: [PATCH v2 RESEND] drivers: hwspinlock: add CSR atlas7 implementation
On Wed, Mar 25, 2015 at 4:03 PM, Barry Song <21cnbao@...il.com> wrote:
> From: Wei Chen <wei.chen@....com>
>
> Add hwspinlock support for the CSR atlas7 SoC.
>
[..]
>
> diff --git a/Documentation/devicetree/bindings/hwspinlock/sirf,hwspinlock.txt b/Documentation/devicetree/bindings/hwspinlock/sirf,hwspinlock.txt
> new file mode 100644
> index 0000000..b22c492
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwspinlock/sirf,hwspinlock.txt
> @@ -0,0 +1,18 @@
> +SIRF Hardware spinlock device Binding
> +-----------------------------------------------
> +
> +Required properties :
> +- compatible : shall contain only one of the following:
> + "sirf,hwspinlock"
> +
> +- reg : the register address of hwspinlock
> +
> +- num-spinlocks : how many spinlocks this device provides
Why is number of spinlocks dynamic?
If you need to keep this it should have the "sirf," prefix.
You should either make a reference to the hwlock.txt pointing out the required
"#hwlock-cells" property, or simply include it here.
> +
> +Example:
> + hwspinlock {
> + compatible = "sirf,hwspinlock";
> + reg = <0x13240000 0x00010000>;
> +
> + num-spinlocks = <30>;
Does the hardware really have 30 locks?
The reason for my question is that we had a similar discussion regarding
this property for the Qualcomm driver, in which I ended up dropping the
property because I wanted the dt binding to describe the actual hardware
and not the limited amount stated in some software design document.
The example is missing #hwlock-cells = <1>;
> + };
> diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
> index 3612cb5..fc400e4 100644
> --- a/drivers/hwspinlock/Kconfig
> +++ b/drivers/hwspinlock/Kconfig
> @@ -29,4 +29,16 @@ config HSEM_U8500
>
> If unsure, say N.
>
> +config HWSPINLOCK_SIRF
I would appreciate if you put this above HSEM_U8500 to keep the list
somewhat sorted.
> + tristate "SIRF Hardware Spinlock device"
> + depends on ARCH_SIRF
> + select HWSPINLOCK
> + help
> + Say y here to support the SIRF Hardware Spinlock device, which
> + provides a synchronisation mechanism for the various processor
s/processor/processors
> + on the SoC.
> +
> + It's safe to say n here if you're not interested in SIRF hardware
> + spinlock or just want a bare minimum kernel.
> +
> endmenu
> diff --git a/drivers/hwspinlock/Makefile b/drivers/hwspinlock/Makefile
> index 93eb64b..472b82d 100644
> --- a/drivers/hwspinlock/Makefile
> +++ b/drivers/hwspinlock/Makefile
> @@ -5,3 +5,4 @@
> obj-$(CONFIG_HWSPINLOCK) += hwspinlock_core.o
> obj-$(CONFIG_HWSPINLOCK_OMAP) += omap_hwspinlock.o
> obj-$(CONFIG_HSEM_U8500) += u8500_hsem.o
> +obj-$(CONFIG_HWSPINLOCK_SIRF) += sirf_hwspinlock.o
Please keep sort order here as well.
> diff --git a/drivers/hwspinlock/sirf_hwspinlock.c b/drivers/hwspinlock/sirf_hwspinlock.c
> new file mode 100644
> index 0000000..b68722a
> --- /dev/null
> +++ b/drivers/hwspinlock/sirf_hwspinlock.c
> @@ -0,0 +1,151 @@
> +/*
> + * SIRF hardware spinlock driver
> + *
> + * Copyright (c) 2014 Cambridge Silicon Radio Limited, a CSR plc group company.
> + *
> + * Licensed under GPLv2.
> + */
> +
> +#include <linux/kernel.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/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +
> +#include "hwspinlock_internal.h"
> +
> +struct sirf_hwspinlock {
> + void __iomem *io_base;
> + struct hwspinlock_device bank;
> +};
> +
> +/* Hardware spinlock register offsets */
> +#define HW_SPINLOCK_RD_DEBUG 0x400
> +#define HW_SPINLOCK_BASE 0x404
> +#define HW_SPINLOCK_OFFSET(x) (HW_SPINLOCK_BASE + 0x4 * (x))
> +
> +/* Possible values of HW_SPINLOCK_REG */
> +#define HW_SPINLOCK_LOCKED 0
> +#define HW_SPINLOCK_FREE 1
> +
> +static int sirf_hwspinlock_trylock(struct hwspinlock *lock)
> +{
> + void __iomem *lock_addr = lock->priv;
> +
> + /* attempt to acquire the lock by reading its value */
> + return (HW_SPINLOCK_FREE == readl(lock_addr));
> +}
> +
> +static void sirf_hwspinlock_unlock(struct hwspinlock *lock)
> +{
> + void __iomem *lock_addr = lock->priv;
> +
> + /* release the lock by writing 0 to it */
> + writel(HW_SPINLOCK_LOCKED, lock_addr);
This looks really wierd, but I assume the naming of the value is in line
with hardware documentation(?)
Instead of having the somewhat confusing names you could replace the
constants with just:
return !!readl(lock_addr);
and
writel(0, lock_addr);
If nothing else because you have the comments there as well...
> +}
> +
> +static void sirf_hwspinlock_relax(struct hwspinlock *lock)
> +{
> + ndelay(50);
> +}
> +
> +static const struct hwspinlock_ops sirf_hwspinlock_ops = {
> + .trylock = sirf_hwspinlock_trylock,
> + .unlock = sirf_hwspinlock_unlock,
> + .relax = sirf_hwspinlock_relax,
> +};
> +
> +static int sirf_hwspinlock_probe(struct platform_device *pdev)
> +{
> + struct sirf_hwspinlock *hwspin;
> + struct hwspinlock *hwlock;
> + u32 num_of_locks;
> + int idx, ret;
> +
> + ret = of_property_read_u32(pdev->dev.of_node,
> + "num-spinlocks", &num_of_locks);
As above; if you need this the property should have a "sirf," prefix.
> + if (ret) {
> + dev_err(&pdev->dev,
> + "Unable to find hwspinlock number. ret=%d\n", ret);
No need to print the error code here.
> + return -ENODEV;
> + }
> +
> + hwspin = devm_kzalloc(&pdev->dev, sizeof(*hwspin) +
> + sizeof(*hwlock) * num_of_locks, GFP_KERNEL);
> + if (!hwspin)
> + return -ENOMEM;
> +
> + /* retrieve io base */
> + hwspin->io_base = of_iomap(pdev->dev.of_node, 0);
> + if (!hwspin->io_base)
> + ret = -ENOMEM;
By using something like the following you can use devres for the ioremap.
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
hwspin->io_base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(hwspin->io_base))
return PTR_ERR(hwspin->io_base);
> +
> + for (idx = 0; idx < num_of_locks; idx++) {
> + hwlock = &hwspin->bank.lock[idx];
> + hwlock->priv = hwspin->io_base + HW_SPINLOCK_OFFSET(idx);
> + }
> +
> + platform_set_drvdata(pdev, hwspin);
> +
> + pm_runtime_enable(&pdev->dev);
> +
> + ret = hwspin_lock_register(&hwspin->bank, &pdev->dev,
> + &sirf_hwspinlock_ops, 0, num_of_locks);
> + if (ret)
> + goto reg_failed;
> +
> + return 0;
> +
> +reg_failed:
> + pm_runtime_disable(&pdev->dev);
> + iounmap(hwspin->io_base);
> +
> + return ret;
> +}
> +
> +static int sirf_hwspinlock_remove(struct platform_device *pdev)
> +{
> + struct sirf_hwspinlock *hwspin = platform_get_drvdata(pdev);
> + int ret;
> +
> + ret = hwspin_lock_unregister(&hwspin->bank);
> + if (ret) {
> + dev_err(&pdev->dev, "%s failed: %d\n", __func__, ret);
> + return ret;
Even if you return an error here the device will still be torn down.
> + }
> +
> + pm_runtime_disable(&pdev->dev);
> +
> + iounmap(hwspin->io_base);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id sirf_hwpinlock_ids[] = {
> + { .compatible = "sirf,hwspinlock", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sirf_hwpinlock_ids);
> +
> +static struct platform_driver sirf_hwspinlock_driver = {
> + .probe = sirf_hwspinlock_probe,
> + .remove = sirf_hwspinlock_remove,
> + .driver = {
> + .name = "atlas7_hwspinlock",
> + .of_match_table = of_match_ptr(sirf_hwpinlock_ids),
> + },
> +};
> +
> +module_platform_driver(sirf_hwspinlock_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("SIRF Hardware spinlock driver");
> +MODULE_AUTHOR("Wei Chen <wei.chen@....com>");
Part of these details I think the patch looks good.
Regards,
Bjorn
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