Re: [PATCH] of: provide of_platform_unpopulate()

From: Rob Herring
Date: Sun Jul 21 2013 - 10:42:36 EST


On 07/19/2013 01:14 PM, Sebastian Andrzej Siewior wrote:
> So I called of_platform_populate() on a device to get each child device
> probed and on rmmod and I need to reverse its doing. After a quick grep
> I did what others did as well and rmmod ended in:
>
> | Unable to handle kernel NULL pointer dereference at virtual address 00000018
> | PC is at release_resource+0x18/0x80
> | Process rmmod (pid: 2005, stack limit = 0xedc30238)
> | [<c003add0>] (release_resource+0x18/0x80) from [<c0300e08>] (platform_device_del+0x78/0xac)
> | [<c0300e08>] (platform_device_del+0x78/0xac) from [<c0301358>] (platform_device_unregister+0xc/0x18)
>
> The problem is that platform_device_del() "releases" each ressource in its
> tree. This does not work on platform_devices created by OF becuase they
> were never added via insert_resource(). As a consequence old->parent in
> __release_resource() is NULL and we explode while accessing ->child.
> So I either I do something completly wrong _or_ nobody here tested the
> rmmod path of their driver.

Wouldn't the correct fix be to call insert_resource somehow? The problem
I have is that while of_platform_populate is all about parsing the DT
and creating devices, the removal side has nothing to do with DT. So
this should not be in the DT code. I think the core device code should
be able to handle removal if the device creation side is done correctly.

It looks to me like of_device_add either needs to call
platform_device_add rather than device_add. I think the device name
setting in platform_device_add should be a nop. If not, a check that the
name is already set could be added.

Rob

>
> This patch provides a common function to unregister / remove devices
> which added to the system via of_platform_populate(). While this works
> now on my test case I have not tested any of the driver I modify here so
> feedback is greatly appreciated.
>
> Cc: Tony Lindgren <tony@xxxxxxxxxxx>
> Cc: Doug Anderson <dianders@xxxxxxxxxxxx>
> Cc: Vivek Gautam <gautam.vivek@xxxxxxxxxxx>
> Cc: Naveen Krishna Chatradhi <ch.naveen@xxxxxxxxxxx>
> Cc: Kukjin Kim <kgene.kim@xxxxxxxxxxx>
> Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
> Cc: Roger Quadros <rogerq@xxxxxx>
> Cc: George Cherian <george.cherian@xxxxxx>
> Cc: Felipe Balbi <balbi@xxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> drivers/bus/omap-ocp2scp.c | 13 ++-----------
> drivers/iio/adc/exynos_adc.c | 15 ++-------------
> drivers/mfd/omap-usb-host.c | 9 +--------
> drivers/of/platform.c | 22 ++++++++++++++++++++++
> drivers/usb/dwc3/dwc3-exynos.c | 11 +----------
> drivers/usb/dwc3/dwc3-omap.c | 12 +-----------
> include/linux/of_platform.h | 4 ++++
> 7 files changed, 33 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/bus/omap-ocp2scp.c b/drivers/bus/omap-ocp2scp.c
> index 5511f98..510bb9e 100644
> --- a/drivers/bus/omap-ocp2scp.c
> +++ b/drivers/bus/omap-ocp2scp.c
> @@ -23,15 +23,6 @@
> #include <linux/of.h>
> #include <linux/of_platform.h>
>
> -static int ocp2scp_remove_devices(struct device *dev, void *c)
> -{
> - struct platform_device *pdev = to_platform_device(dev);
> -
> - platform_device_unregister(pdev);
> -
> - return 0;
> -}
> -
> static int omap_ocp2scp_probe(struct platform_device *pdev)
> {
> int ret;
> @@ -51,7 +42,7 @@ static int omap_ocp2scp_probe(struct platform_device *pdev)
> return 0;
>
> err0:
> - device_for_each_child(&pdev->dev, NULL, ocp2scp_remove_devices);
> + of_platform_unpopulate(&pdev->dev);
>
> return ret;
> }
> @@ -59,7 +50,7 @@ static int omap_ocp2scp_probe(struct platform_device *pdev)
> static int omap_ocp2scp_remove(struct platform_device *pdev)
> {
> pm_runtime_disable(&pdev->dev);
> - device_for_each_child(&pdev->dev, NULL, ocp2scp_remove_devices);
> + of_platform_unpopulate(&pdev->dev);
>
> return 0;
> }
> diff --git a/drivers/iio/adc/exynos_adc.c b/drivers/iio/adc/exynos_adc.c
> index 9809fc9..10248e1 100644
> --- a/drivers/iio/adc/exynos_adc.c
> +++ b/drivers/iio/adc/exynos_adc.c
> @@ -216,15 +216,6 @@ static const struct iio_chan_spec exynos_adc_iio_channels[] = {
> ADC_CHANNEL(9, "adc9"),
> };
>
> -static int exynos_adc_remove_devices(struct device *dev, void *c)
> -{
> - struct platform_device *pdev = to_platform_device(dev);
> -
> - platform_device_unregister(pdev);
> -
> - return 0;
> -}
> -
> static void exynos_adc_hw_init(struct exynos_adc *info)
> {
> u32 con1, con2;
> @@ -357,8 +348,7 @@ static int exynos_adc_probe(struct platform_device *pdev)
> return 0;
>
> err_of_populate:
> - device_for_each_child(&pdev->dev, NULL,
> - exynos_adc_remove_devices);
> + of_platform_unpopulate(&pdev->dev);
> regulator_disable(info->vdd);
> clk_disable_unprepare(info->clk);
> err_iio_dev:
> @@ -375,8 +365,7 @@ static int exynos_adc_remove(struct platform_device *pdev)
> struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> struct exynos_adc *info = iio_priv(indio_dev);
>
> - device_for_each_child(&pdev->dev, NULL,
> - exynos_adc_remove_devices);
> + of_platform_unpopulate(&pdev->dev);
> regulator_disable(info->vdd);
> clk_disable_unprepare(info->clk);
> writel(0, info->enable_reg);
> diff --git a/drivers/mfd/omap-usb-host.c b/drivers/mfd/omap-usb-host.c
> index 759fae3..bb26cea 100644
> --- a/drivers/mfd/omap-usb-host.c
> +++ b/drivers/mfd/omap-usb-host.c
> @@ -832,13 +832,6 @@ static int usbhs_omap_probe(struct platform_device *pdev)
> return ret;
> }
>
> -static int usbhs_omap_remove_child(struct device *dev, void *data)
> -{
> - dev_info(dev, "unregistering\n");
> - platform_device_unregister(to_platform_device(dev));
> - return 0;
> -}
> -
> /**
> * usbhs_omap_remove - shutdown processing for UHH & TLL HCDs
> * @pdev: USB Host Controller being removed
> @@ -871,7 +864,7 @@ static int usbhs_omap_remove(struct platform_device *pdev)
> pm_runtime_disable(&pdev->dev);
>
> /* remove children */
> - device_for_each_child(&pdev->dev, NULL, usbhs_omap_remove_child);
> + of_platform_unpopulate(&pdev->dev);
> return 0;
> }
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index e0a6514..9cbb0c3 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -473,4 +473,26 @@ int of_platform_populate(struct device_node *root,
> return rc;
> }
> EXPORT_SYMBOL_GPL(of_platform_populate);
> +
> +static int of_remove_populated_child(struct device *dev, void *d)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> +
> + of_device_unregister(pdev);
> + return 0;
> +}
> +/**
> + * of_platform_unpopulate() - Remove populated devices.
> + * @parent: parent of the populated devices.
> + *
> + * The reverse of of_platform_populate() and can only be used a parent was
> + * specified while invoking the former.
> + */
> +void of_platform_unpopulate(struct device *parent)
> +{
> + if (WARN_ON(!parent))
> + return;
> + device_for_each_child(parent, NULL, of_remove_populated_child);
> +}
> +EXPORT_SYMBOL_GPL(of_platform_unpopulate);
> #endif /* CONFIG_OF_ADDRESS */
> diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
> index 8ce9d7f..2bf5664 100644
> --- a/drivers/usb/dwc3/dwc3-exynos.c
> +++ b/drivers/usb/dwc3/dwc3-exynos.c
> @@ -86,15 +86,6 @@ static int dwc3_exynos_register_phys(struct dwc3_exynos *exynos)
> return ret;
> }
>
> -static int dwc3_exynos_remove_child(struct device *dev, void *unused)
> -{
> - struct platform_device *pdev = to_platform_device(dev);
> -
> - platform_device_unregister(pdev);
> -
> - return 0;
> -}
> -
> static int dwc3_exynos_probe(struct platform_device *pdev)
> {
> struct dwc3_exynos *exynos;
> @@ -164,7 +155,7 @@ static int dwc3_exynos_remove(struct platform_device *pdev)
> {
> struct dwc3_exynos *exynos = platform_get_drvdata(pdev);
>
> - device_for_each_child(&pdev->dev, NULL, dwc3_exynos_remove_child);
> + of_platform_unpopulate(&pdev->dev);
> platform_device_unregister(exynos->usb2_phy);
> platform_device_unregister(exynos->usb3_phy);
>
> diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
> index 077f110..8688613 100644
> --- a/drivers/usb/dwc3/dwc3-omap.c
> +++ b/drivers/usb/dwc3/dwc3-omap.c
> @@ -327,15 +327,6 @@ static irqreturn_t dwc3_omap_interrupt(int irq, void *_omap)
> return IRQ_HANDLED;
> }
>
> -static int dwc3_omap_remove_core(struct device *dev, void *c)
> -{
> - struct platform_device *pdev = to_platform_device(dev);
> -
> - platform_device_unregister(pdev);
> -
> - return 0;
> -}
> -
> static void dwc3_omap_enable_irqs(struct dwc3_omap *omap)
> {
> u32 reg;
> @@ -529,8 +520,7 @@ static int dwc3_omap_remove(struct platform_device *pdev)
> dwc3_omap_disable_irqs(omap);
> pm_runtime_put_sync(&pdev->dev);
> pm_runtime_disable(&pdev->dev);
> - device_for_each_child(&pdev->dev, NULL, dwc3_omap_remove_core);
> -
> + of_platform_unpopulate(&pdev->dev);
> return 0;
> }
>
> diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
> index 05cb4a9..e354f9c 100644
> --- a/include/linux/of_platform.h
> +++ b/include/linux/of_platform.h
> @@ -72,6 +72,7 @@ extern int of_platform_populate(struct device_node *root,
> const struct of_device_id *matches,
> const struct of_dev_auxdata *lookup,
> struct device *parent);
> +extern void of_platform_unpopulate(struct device *parent);
> #else
> static inline int of_platform_populate(struct device_node *root,
> const struct of_device_id *matches,
> @@ -80,6 +81,9 @@ static inline int of_platform_populate(struct device_node *root,
> {
> return -ENODEV;
> }
> +static inline void of_platform_unpopulate(struct device *parent)
> +{
> +}
> #endif
>
> #endif /* _LINUX_OF_PLATFORM_H */
>

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