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Date: Tue, 23 Sep 2014 15:59:43 +0530
From: Pankaj Dubey <pankaj.dubey@...sung.com>
To: 'Dong Aisheng' <b29396@...escale.com>, arnd@...db.de
Cc: linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
lee.jones@...aro.org, 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
Hi Dong,
On Monday, September 22, 2014, Dong Aisheng wrote,
> On Mon, Sep 22, 2014 at 10:10:07AM +0530, Pankaj Dubey wrote:
[snip]
> > -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.
>
If you are referring to use "of_platform_device_create", then I am afraid
that it can't be used
in very early stage. For example, current patch I tested by calling
syscon_lookup_by_phandle from
"init_irq" hook of machine_desc, and it worked well, but If I use
"of_platform_device_create"
instead of dummy device, it fails to create pdev and this I verified on
Exynos platform. The reason
I selected "init_irq" is because this comes just before smp init and where
once we tried to get regmap handle,
but could not do so.
Also if it was just a matter of creating platform_device at early stage then
early initialization of
syscon could have been solved till now.
So I would suggest if we really want this patch to cover early
initialization of syscon
(which is not it's main purpose) current patch is sufficient.
@Arnd, since I have addressed crash issue as reported by Dong Aisheng, I
would like to take your ack,
but since there are some more code changes other than what you suggested I
request you to check this
and if you are ok, then I would like to your ack so that I can request to
maintainer for taking this patch.
Thanks,
Pankaj Dubey
> 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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