Commit 1e29af62 authored by Andres Salomon's avatar Andres Salomon Committed by Samuel Ortiz
Browse files

mfd: Add refcounting support to mfd_cells 



This provides convenience functions for sharing of cells across
multiple mfd clients.  Mfd drivers can provide enable/disable hooks
to actually tweak the hardware, and clients can call
mfd_shared_cell_{en,dis}able without having to worry about whether
or not another client happens to have enabled or disabled the
cell/hardware.

Note that this is purely optional; drivers can continue to use
the mfd_cell's enable/disable hooks for their own purposes, if
desired.

Signed-off-by: default avatarAndres Salomon <dilinger@queued.net>
Signed-off-by: default avatarSamuel Ortiz <sameo@linux.intel.com>
parent dcb50e83

drivers/mfd/mfd-core.c

+60 −4
Original line number Diff line number Diff line
@@ -18,6 +18,43 @@ 
#include <linux/pm_runtime.h>

#include <linux/slab.h>



int mfd_shared_cell_enable(struct platform_device *pdev)

{

	const struct mfd_cell *cell = mfd_get_cell(pdev);

	int err = 0;



	/* only call enable hook if the cell wasn't previously enabled */

	if (atomic_inc_return(cell->usage_count) == 1)

		err = cell->enable(pdev);



	/* if the enable hook failed, decrement counter to allow retries */

	if (err)

		atomic_dec(cell->usage_count);



	return err;

}

EXPORT_SYMBOL(mfd_shared_cell_enable);



int mfd_shared_cell_disable(struct platform_device *pdev)

{

	const struct mfd_cell *cell = mfd_get_cell(pdev);

	int err = 0;



	/* only disable if no other clients are using it */

	if (atomic_dec_return(cell->usage_count) == 0)

		err = cell->disable(pdev);



	/* if the disable hook failed, increment to allow retries */

	if (err)

		atomic_inc(cell->usage_count);



	/* sanity check; did someone call disable too many times? */

	WARN_ON(atomic_read(cell->usage_count) < 0);



	return err;

}

EXPORT_SYMBOL(mfd_shared_cell_disable);



static int mfd_add_device(struct device *parent, int id,

			  const struct mfd_cell *cell,

			  struct resource *mem_base,
@@ -96,14 +133,22 @@ fail_alloc: 
}



int mfd_add_devices(struct device *parent, int id,

		    const struct mfd_cell *cells, int n_devs,

		    struct mfd_cell *cells, int n_devs,

		    struct resource *mem_base,

		    int irq_base)

{

	int i;

	int ret = 0;

	atomic_t *cnts;



	/* initialize reference counting for all cells */

	cnts = kcalloc(sizeof(*cnts), n_devs, GFP_KERNEL);

	if (!cnts)

		return -ENOMEM;



	for (i = 0; i < n_devs; i++) {

		atomic_set(&cnts[i], 0);

		cells[i].usage_count = &cnts[i];

		ret = mfd_add_device(parent, id, cells + i, mem_base, irq_base);

		if (ret)

			break;
@@ -116,15 +161,26 @@ int mfd_add_devices(struct device *parent, int id, 
}

EXPORT_SYMBOL(mfd_add_devices);



static int mfd_remove_devices_fn(struct device *dev, void *unused)

static int mfd_remove_devices_fn(struct device *dev, void *c)

{

	platform_device_unregister(to_platform_device(dev));

	struct platform_device *pdev = to_platform_device(dev);

	const struct mfd_cell *cell = mfd_get_cell(pdev);

	atomic_t **usage_count = c;



	/* find the base address of usage_count pointers (for freeing) */

	if (!*usage_count || (cell->usage_count < *usage_count))

		*usage_count = cell->usage_count;



	platform_device_unregister(pdev);

	return 0;

}



void mfd_remove_devices(struct device *parent)

{

	device_for_each_child(parent, NULL, mfd_remove_devices_fn);

	atomic_t *cnts = NULL;



	device_for_each_child(parent, &cnts, mfd_remove_devices_fn);

	kfree(cnts);

}

EXPORT_SYMBOL(mfd_remove_devices);

include/linux/mfd/core.h

+13 −1
Original line number Diff line number Diff line
@@ -25,8 +25,11 @@ struct mfd_cell { 
	const char		*name;

	int			id;



	/* refcounting for multiple drivers to use a single cell */

	atomic_t		*usage_count;

	int			(*enable)(struct platform_device *dev);

	int			(*disable)(struct platform_device *dev);



	int			(*suspend)(struct platform_device *dev);

	int			(*resume)(struct platform_device *dev);
@@ -50,6 +53,15 @@ struct mfd_cell { 
	bool			pm_runtime_no_callbacks;

};



/*

 * Convenience functions for clients using shared cells.  Refcounting

 * happens automatically, with the cell's enable/disable callbacks

 * being called only when a device is first being enabled or no other

 * clients are making use of it.

 */

extern int mfd_shared_cell_enable(struct platform_device *pdev);

extern int mfd_shared_cell_disable(struct platform_device *pdev);



/*

 * Given a platform device that's been created by mfd_add_devices(), fetch

 * the mfd_cell that created it.
@@ -69,7 +81,7 @@ static inline void *mfd_get_data(struct platform_device *pdev) 
}



extern int mfd_add_devices(struct device *parent, int id,

			   const struct mfd_cell *cells, int n_devs,

			   struct mfd_cell *cells, int n_devs,

			   struct resource *mem_base,

			   int irq_base);

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