Messages in this thread | | | Date | Mon, 14 Dec 2020 11:06:24 -0600 | From | Bjorn Andersson <> | Subject | Re: [PATCH v4 2/2] hwspinlock: add sun8i hardware spinlock support |
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On Fri 11 Dec 08:40 CST 2020, Samuel Holland wrote:
> On 12/11/20 3:03 AM, Maxime Ripard wrote: > > Hi, > > > > On Fri, Dec 11, 2020 at 09:24:15AM +0100, Wilken Gottwalt wrote: > >> Adds the sun8i_hwspinlock driver for the hardware spinlock unit found in > >> most of the sun8i compatible SoCs. > >> > >> This unit provides at least 32 spinlocks in hardware. The implementation > >> supports 32, 64, 128 or 256 32bit registers. A lock can be taken by > >> reading a register and released by writing a 0 to it. This driver > >> supports all 4 spinlock setups, but for now only the first setup (32 > >> locks) seem to exist in available devices. This spinlock unit is shared > >> between all ARM cores and the embedded OpenRisc AR100 core. All of them > >> can take/release a lock with a single cycle operation. It can be used to > >> sync access to devices shared by the ARM cores and the OpenRisc core. > >> > >> There are two ways to check if a lock is taken. The first way is to read > >> a lock. If a 0 is returned, the lock was free and is taken now. If an 1 > >> is returned, the caller has to try again. Which means the lock is taken. > >> The second way is to read a 32bit wide status register where every bit > >> represents one of the 32 first locks. According to the datasheets this > >> status register supports only the 32 first locks. This is the reason the > >> first way (lock read/write) approach is used to be able to cover all 256 > >> locks in future devices. The driver also reports the amount of supported > >> locks via debugfs. > >> > >> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net> > >> --- > >> Changes in v4: > >> - further simplified driver > >> - fixed an add_action_and_reset_ function issue > >> - changed bindings from sun8i-hwspinlock to sun8i-a33-hwspinlock > >> > >> Changes in v3: > >> - moved test description to cover letter > >> - changed name and symbols from sunxi to sun8i > >> - improved driver description > >> - further simplified driver > >> - fully switched to devm_* and devm_add_action_* functions > >> > >> Changes in v2: > >> - added suggestions from Bjorn Andersson and Maxime Ripard > >> - provided better driver and test description > >> --- > >> MAINTAINERS | 6 + > >> drivers/hwspinlock/Kconfig | 9 ++ > >> drivers/hwspinlock/Makefile | 1 + > >> drivers/hwspinlock/sun8i_hwspinlock.c | 197 ++++++++++++++++++++++++++ > >> 4 files changed, 213 insertions(+) > >> create mode 100644 drivers/hwspinlock/sun8i_hwspinlock.c > >> > >> diff --git a/MAINTAINERS b/MAINTAINERS > >> index ebe4829cdd4d..46846113f1eb 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/sun8i-hwspinlock.yaml > >> +F: drivers/hwspinlock/sun8i_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..b03fd99aab32 100644 > >> --- a/drivers/hwspinlock/Kconfig > >> +++ b/drivers/hwspinlock/Kconfig > >> @@ -55,6 +55,15 @@ config HWSPINLOCK_STM32 > >> > >> If unsure, say N. > >> > >> +config HWSPINLOCK_SUN8I > >> + tristate "SUN8I Hardware Spinlock device" > >> + depends on ARCH_SUNXI || COMPILE_TEST > >> + help > >> + Say y here to support the SUN8I Hardware Spinlock device which can be > >> + found in most of the sun8i compatible Allwinner 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..3496648d9257 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-$(CONFIG_HWSPINLOCK_SUN8I) += sun8i_hwspinlock.o > >> obj-$(CONFIG_HSEM_U8500) += u8500_hsem.o > >> diff --git a/drivers/hwspinlock/sun8i_hwspinlock.c b/drivers/hwspinlock/sun8i_hwspinlock.c > >> new file mode 100644 > >> index 000000000000..878dae6f1763 > >> --- /dev/null > >> +++ b/drivers/hwspinlock/sun8i_hwspinlock.c > >> @@ -0,0 +1,197 @@ > >> +// SPDX-License-Identifier: GPL-2.0-or-later > >> +/* > >> + * sun8i_hwspinlock.c - hardware spinlock driver for sun8i compatible Allwinner SoCs > >> + * Copyright (C) 2020 Wilken Gottwalt <wilken.gottwalt@posteo.net> > >> + */ > >> + > >> +#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 "sun8i_hwspinlock" > >> + > >> +#define SPINLOCK_BASE_ID 0 /* there is only one hwspinlock device per SoC */ > >> +#define SPINLOCK_SYSSTATUS_REG 0x0000 > >> +#define SPINLOCK_LOCK_REGN 0x0100 > >> +#define SPINLOCK_NOTTAKEN 0 > >> + > >> +struct sun8i_hwspinlock_data { > >> + struct hwspinlock_device *bank; > >> + struct reset_control *reset; > >> + struct clk *ahb_clk; > >> + struct dentry *debugfs; > >> + int nlocks; > >> +}; > >> + > >> +#ifdef CONFIG_DEBUG_FS > >> + > >> +static int hwlocks_supported_show(struct seq_file *seqf, void *unused) > >> +{ > >> + struct sun8i_hwspinlock_data *priv = seqf->private; > >> + > >> + seq_printf(seqf, "%d\n", priv->nlocks); > >> + > >> + return 0; > >> +} > >> +DEFINE_SHOW_ATTRIBUTE(hwlocks_supported); > >> + > >> +static void sun8i_hwspinlock_debugfs_init(struct sun8i_hwspinlock_data *priv) > >> +{ > >> + priv->debugfs = debugfs_create_dir(DRIVER_NAME, NULL); > > > > debugfs_create_dir can return an error pointer, you should check that > > and return the error code if it does > > > >> + debugfs_create_file("supported", 0444, priv->debugfs, priv, &hwlocks_supported_fops); > > > > And debugfs_create_file can fail as well > > My understanding was that you're not supposed to check the return values > of debugfs_create_* functions, because debugfs is just for debugging and > shouldn't prevent the driver from loading. >
That is correct, the debugfs api is written with the expectation that you shouldn't do error handling.
> >> +} > >> + > >> +#else > >> + > >> +static void sun8i_hwspinlock_debugfs_init(struct sun8i_hwspinlock_data *priv) > >> +{ > >> +} > >> + > >> +#endif > >> + > >> +static int sun8i_hwspinlock_trylock(struct hwspinlock *lock) > >> +{ > >> + void __iomem *lock_addr = lock->priv; > >> + > >> + return (readl(lock_addr) == SPINLOCK_NOTTAKEN); > >> +} > >> + > >> +static void sun8i_hwspinlock_unlock(struct hwspinlock *lock) > >> +{ > >> + void __iomem *lock_addr = lock->priv; > >> + > >> + writel(SPINLOCK_NOTTAKEN, lock_addr); > >> +} > >> + > >> +static const struct hwspinlock_ops sun8i_hwspinlock_ops = { > >> + .trylock = sun8i_hwspinlock_trylock, > >> + .unlock = sun8i_hwspinlock_unlock, > >> +}; > >> + > >> +static void sun8i_hwspinlock_disable(void *data) > >> +{ > >> + struct sun8i_hwspinlock_data *priv = data; > >> + > >> + debugfs_remove_recursive(priv->debugfs); > >> + reset_control_assert(priv->reset); > >> + clk_disable_unprepare(priv->ahb_clk); > >> +} > >> + > >> +static int sun8i_hwspinlock_probe(struct platform_device *pdev) > >> +{ > >> + struct sun8i_hwspinlock_data *priv; > >> + struct hwspinlock *hwlock; > >> + void __iomem *io_base; > >> + u32 num_banks; > >> + int err, i; > >> + > >> + io_base = devm_platform_ioremap_resource(pdev, SPINLOCK_BASE_ID); > >> + if (IS_ERR(io_base)) > >> + return PTR_ERR(io_base); > >> + > >> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); > >> + if (!priv) > >> + return -ENOMEM; > >> + > >> + priv->ahb_clk = devm_clk_get(&pdev->dev, "ahb"); > >> + if (IS_ERR(priv->ahb_clk)) { > >> + err = PTR_ERR(priv->ahb_clk); > >> + dev_err(&pdev->dev, "unable to get AHB clock (%d)\n", err); > >> + return err; > >> + } > >> + > >> + priv->reset = devm_reset_control_get(&pdev->dev, "ahb"); > >> + if (IS_ERR(priv->reset)) > >> + return dev_err_probe(&pdev->dev, PTR_ERR(priv->reset), > >> + "unable to get reset control\n"); > >> + > >> + 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_clk); > >> + if (err) { > >> + dev_err(&pdev->dev, "unable to prepare AHB clk (%d)\n", err); > >> + return err; > >> + } > >> + > >> + sun8i_hwspinlock_debugfs_init(priv); > >> + > >> + err = devm_add_action_or_reset(&pdev->dev, sun8i_hwspinlock_disable, priv); > >> + if (err) { > >> + dev_err(&pdev->dev, "unable to add disable action\n"); > >> + return err; > >> + } > > > > That part still doesn't really work: if clk_prepare_enable fails, you'll > > end up removing the debugfs files that haven't been added yet, and > > you'll disable the clock that hasn't been enabled. > > > > I'm not sure you need to be that smart: just add a label and a goto to > > the proper cleaning stuff > > I would also suggest implementing the driver's .remove callback instead > of allocating additional memory for a devm action. >
I have a feeling that I might have asked for the use of devm helpers. But afaict we still need a remove function to remove the debugfs stuff.
So I agree with your ask.
Regards, Bjorn
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