Re: [PATCH v2 RESEND] drivers: hwspinlock: add CSR atlas7 implementation

[Barry Song]

2015-05-07 2:13 GMT+08:00 Bjorn Andersson <bjorn@xxxxxxx>:
> On Wed, Mar 25, 2015 at 4:03 PM, Barry Song <21cnbao@xxxxxxxxx> wrote:
>> From: Wei Chen <wei.chen@xxxxxxx>
>>
>> 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.

we would like to move it a MARCO in drivers directly just like other
spinlock drivers.
>
>
> You should either make a reference to the hwlock.txt pointing out the required
> "#hwlock-cells" property, or simply include it here.

yes. this has been discussed in another thread and Suman posted same comments.

>
>> +
>> +Example:
>> +       hwspinlock {
>> +               compatible = "sirf,hwspinlock";
>> +               reg = <0x13240000 0x00010000>;
>> +
>> +               num-spinlocks = <30>;
>
> Does the hardware really have 30 locks?

yes.

>
>
> 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 channel number should be HW? not SW?

>
> 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.
>

looks fine.

>> +       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.

looks fine.

>
>> 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(?)

looks wired too. will double-check.

>
>
> 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);

the benefit should be avoiding kfree. this should be a coding style
issue. i think this of_iomap is following the existing omap driver.

>
>> +
>> +       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.
>

so what is your suggestion about this? do you think the unregister
should be "void" as other unregister functions?

>> +       }
>> +
>> +       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@xxxxxxx>");
>
> Part of these details I think the patch looks good.
>
> Regards,
> Bjorn

-barry
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