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Message-ID: <20140922091925.GA19778@shlinux1.ap.freescale.net>
Date: Mon, 22 Sep 2014 17:19:30 +0800
From: Dong Aisheng <b29396@...escale.com>
To: Pankaj Dubey <pankaj.dubey@...sung.com>
CC: <linux-arm-kernel@...ts.infradead.org>,
<linux-samsung-soc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <lee.jones@...aro.org>,
<arnd@...db.de>, <tomasz.figa@...il.com>, <linux@....linux.org.uk>,
<vikas.sajjan@...sung.com>, <joshi@...sung.com>,
<naushad@...sung.com>, <thomas.ab@...sung.com>,
<chow.kim@...sung.com>, <kgene.kim@...sung.com>,
<Li.Xiubo@...escale.com>
Subject: Re: [PATCH v5] mfd: syscon: Decouple syscon interface from
platform devices
On Mon, Sep 22, 2014 at 10:10:07AM +0530, Pankaj Dubey wrote:
> Currently a syscon entity can be only registered directly through a
> platform device that binds to a dedicated syscon driver. However in
> certain use cases it is desirable to make a device used with another
> driver a syscon interface provider.
>
> For example, certain SoCs (e.g. Exynos) contain system controller
> blocks which perform various functions such as power domain control,
> CPU power management, low power mode control, but in addition contain
> certain IP integration glue, such as various signal masks,
> coprocessor power control, etc. In such case, there is a need to have
> a dedicated driver for such system controller but also share registers
> with other drivers. The latter is where the syscon interface is helpful.
>
> In case of DT based platforms, this patch decouples syscon object from
> syscon platform driver, and allows to create syscon objects first time
> when it is required by calling of syscon_regmap_lookup_by APIs and keep
> a list of such syscon objects along with syscon provider device_nodes
> and regmap handles.
>
> For non-DT based platforms, this patch keeps syscon platform driver
> structure where is can be probed and such non-DT based drivers can use
> syscon_regmap_lookup_by_pdev API and get access to regmap handles.
> Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> we can completly remove platform driver of syscon, and keep only helper
> functions to get regmap handles.
>
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Suggested-by: Tomasz Figa <tomasz.figa@...il.com>
> Tested-by: Vivek Gautam <gautam.vivek@...sung.com>
> Tested-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
> Patch v4 and related discussions can be found here [1].
>
> Changes since v4:
> - Addressed Tomasz Figa's comments for v4.
> - Added error handing in of_syscon_register function.
> - Using devm_regmap_init_mmio instead of regmap_init_mmio.
>
> Changes since v3:
> - Addressed Arnd's comment for v2.
> - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
> - For early users created dummy platform device.
>
> Changes since v2:
> - Added back platform device support from syscon, with one change that
> syscon will not be probed for DT based platform.
> - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
> users of syscon will not be broken.
> - Removed unwanted change in syscon.h.
> - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
> Arnd Bergmann.
> - Added Tested-by of Vivek Gautam for testing on Exynos platform.
>
> Changes since v1:
> - Removed of_syscon_unregister function.
> - Modified of_syscon_register function and it will be used by syscon.c
> to create syscon objects whenever required.
> - Removed platform device support from syscon.
> - Removed syscon_regmap_lookup_by_pdevname API support.
> - As there are significant changes w.r.t patchset v1, I am taking over
> author for this patchset from Tomasz Figa.
>
> [1]: https://lkml.org/lkml/2014/9/19/267
>
> drivers/mfd/syscon.c | 107 +++++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 85 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index ca15878..0b17f50 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -15,6 +15,7 @@
> #include <linux/err.h>
> #include <linux/io.h>
> #include <linux/module.h>
> +#include <linux/list.h>
> #include <linux/of.h>
> #include <linux/of_address.h>
> #include <linux/of_platform.h>
> @@ -22,31 +23,105 @@
> #include <linux/platform_device.h>
> #include <linux/regmap.h>
> #include <linux/mfd/syscon.h>
> +#include <linux/slab.h>
>
> static struct platform_driver syscon_driver;
>
> +static DEFINE_SPINLOCK(syscon_list_slock);
> +static LIST_HEAD(syscon_list);
> +
> struct syscon {
> + struct device_node *np;
> struct regmap *regmap;
> + struct list_head list;
> +};
> +
> +static struct regmap_config syscon_regmap_config = {
> + .reg_bits = 32,
> + .val_bits = 32,
> + .reg_stride = 4,
> };
>
> -static int syscon_match_node(struct device *dev, void *data)
> +static struct syscon *of_syscon_register(struct device_node *np)
> {
> - struct device_node *dn = data;
> + struct platform_device *pdev = NULL;
> + struct syscon *syscon;
> + struct regmap *regmap;
> + void __iomem *base;
> + int ret;
> +
> + if (!of_device_is_compatible(np, "syscon"))
> + return ERR_PTR(-EINVAL);
> +
> + syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> + if (!syscon)
> + return ERR_PTR(-ENOMEM);
> +
> + base = of_iomap(np, 0);
> + if (!base) {
> + ret = -ENOMEM;
> + goto err_map;
> + }
> +
> + /* if device is already populated and available then use it */
> + pdev = of_find_device_by_node(np);
> + if (!pdev) {
> + /* for early users create dummy syscon device and use it */
> + pdev = platform_device_alloc("dummy-syscon", -1);
Can we create specific devices for each syscon device?
That looks more reasonable to me.
Then we can dump registers in regmap debugfs more clearly, just like other devices.
And i think it's better to follow device tree way to generate devices from node.
If DT core find a device is already created, it can ignore that device to avoid
creating duplicated device during of_platform_populate.
Regards
Dong Aisheng
> + if (!pdev) {
> + ret = -ENOMEM;
> + goto err_pdev;
> + }
> + pdev->dev.of_node = of_node_get(np);
> + }
> +
> + regmap = devm_regmap_init_mmio(&pdev->dev, base, &syscon_regmap_config);
> + if (IS_ERR(regmap)) {
> + dev_err(&pdev->dev, "regmap init failed\n");
> + ret = PTR_ERR(regmap);
> + goto err_regmap;
> + }
> +
> + syscon->regmap = regmap;
> + syscon->np = np;
>
> - return (dev->of_node == dn) ? 1 : 0;
> + spin_lock(&syscon_list_slock);
> + list_add_tail(&syscon->list, &syscon_list);
> + spin_unlock(&syscon_list_slock);
> +
> + return syscon;
> +
> +err_regmap:
> + if (!strcmp(pdev->name, "dummy-syscon")) {
> + of_node_put(np);
> + platform_device_put(pdev);
> + }
> +err_pdev:
> + iounmap(base);
> +err_map:
> + kfree(syscon);
> + return ERR_PTR(ret);
> }
>
> struct regmap *syscon_node_to_regmap(struct device_node *np)
> {
> - struct syscon *syscon;
> - struct device *dev;
> + struct syscon *entry, *syscon = NULL;
>
> - dev = driver_find_device(&syscon_driver.driver, NULL, np,
> - syscon_match_node);
> - if (!dev)
> - return ERR_PTR(-EPROBE_DEFER);
> + spin_lock(&syscon_list_slock);
>
> - syscon = dev_get_drvdata(dev);
> + list_for_each_entry(entry, &syscon_list, list)
> + if (entry->np == np) {
> + syscon = entry;
> + break;
> + }
> +
> + spin_unlock(&syscon_list_slock);
> +
> + if (!syscon)
> + syscon = of_syscon_register(np);
> +
> + if (IS_ERR(syscon))
> + return ERR_CAST(syscon);
>
> return syscon->regmap;
> }
> @@ -110,17 +185,6 @@ struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
> }
> EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
>
> -static const struct of_device_id of_syscon_match[] = {
> - { .compatible = "syscon", },
> - { },
> -};
> -
> -static struct regmap_config syscon_regmap_config = {
> - .reg_bits = 32,
> - .val_bits = 32,
> - .reg_stride = 4,
> -};
> -
> static int syscon_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> @@ -167,7 +231,6 @@ static struct platform_driver syscon_driver = {
> .driver = {
> .name = "syscon",
> .owner = THIS_MODULE,
> - .of_match_table = of_syscon_match,
> },
> .probe = syscon_probe,
> .id_table = syscon_ids,
> --
> 1.7.9.5
>
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