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Date: Mon, 21 Oct 2019 13:33:53 +0100
From: Daniel Thompson <daniel.thompson@...aro.org>
To: Lee Jones <lee.jones@...aro.org>
Cc: arnd@...db.de, broonie@...nel.org, linus.walleij@...aro.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
baohua@...nel.org, stephan@...hold.net
Subject: Re: [PATCH v2 8/9] mfd: mfd-core: Remove usage counting for
.{en,dis}able() call-backs
On Mon, Oct 21, 2019 at 11:58:21AM +0100, Lee Jones wrote:
> The MFD implementation for reference counting was complex and unnecessary.
> There was only one bona fide user which has now been converted to handle
> the process in a different way. Any future resource protection, shared
> enablement functions should be handed by the parent device, rather than
> through the MFD subsystem API.
>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>
> ---
> drivers/mfd/mfd-core.c | 57 +++++++---------------------------------
> include/linux/mfd/core.h | 2 --
> 2 files changed, 9 insertions(+), 50 deletions(-)
>
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 90b43b44a15a..5d56015baeeb 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -26,53 +26,31 @@ static struct device_type mfd_dev_type = {
> int mfd_cell_enable(struct platform_device *pdev)
> {
> const struct mfd_cell *cell = mfd_get_cell(pdev);
> - int err = 0;
>
> if (!cell->enable) {
> dev_dbg(&pdev->dev, "No .enable() call-back registered\n");
> return 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;
> + return cell->enable(pdev);
> }
> EXPORT_SYMBOL(mfd_cell_enable);
>
> int mfd_cell_disable(struct platform_device *pdev)
> {
> const struct mfd_cell *cell = mfd_get_cell(pdev);
> - int err = 0;
>
> if (!cell->enable) {
> dev_dbg(&pdev->dev, "No .disable() call-back registered\n");
> return 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;
> + return cell->disable(pdev);
> }
> EXPORT_SYMBOL(mfd_cell_disable);
>
> static int mfd_platform_add_cell(struct platform_device *pdev,
> - const struct mfd_cell *cell,
> - atomic_t *usage_count)
> + const struct mfd_cell *cell)
> {
> if (!cell)
> return 0;
> @@ -81,7 +59,6 @@ static int mfd_platform_add_cell(struct platform_device *pdev,
> if (!pdev->mfd_cell)
> return -ENOMEM;
>
> - pdev->mfd_cell->usage_count = usage_count;
> return 0;
> }
>
> @@ -144,7 +121,7 @@ static inline void mfd_acpi_add_device(const struct mfd_cell *cell,
> #endif
>
> static int mfd_add_device(struct device *parent, int id,
> - const struct mfd_cell *cell, atomic_t *usage_count,
> + const struct mfd_cell *cell,
> struct resource *mem_base,
> int irq_base, struct irq_domain *domain)
> {
> @@ -206,7 +183,7 @@ static int mfd_add_device(struct device *parent, int id,
> goto fail_alias;
> }
>
> - ret = mfd_platform_add_cell(pdev, cell, usage_count);
> + ret = mfd_platform_add_cell(pdev, cell);
> if (ret)
> goto fail_alias;
>
> @@ -296,16 +273,9 @@ int mfd_add_devices(struct device *parent, int id,
> {
> int i;
> int ret;
> - atomic_t *cnts;
> -
> - /* initialize reference counting for all cells */
> - cnts = kcalloc(n_devs, sizeof(*cnts), GFP_KERNEL);
> - if (!cnts)
> - return -ENOMEM;
>
> for (i = 0; i < n_devs; i++) {
> - atomic_set(&cnts[i], 0);
> - ret = mfd_add_device(parent, id, cells + i, cnts + i, mem_base,
> + ret = mfd_add_device(parent, id, cells + i, mem_base,
> irq_base, domain);
> if (ret)
> goto fail;
> @@ -316,17 +286,15 @@ int mfd_add_devices(struct device *parent, int id,
> fail:
> if (i)
> mfd_remove_devices(parent);
> - else
> - kfree(cnts);
> +
> return ret;
> }
> EXPORT_SYMBOL(mfd_add_devices);
>
> -static int mfd_remove_devices_fn(struct device *dev, void *c)
> +static int mfd_remove_devices_fn(struct device *dev, void *data)
> {
> struct platform_device *pdev;
> const struct mfd_cell *cell;
> - atomic_t **usage_count = c;
>
> if (dev->type != &mfd_dev_type)
> return 0;
> @@ -337,20 +305,13 @@ static int mfd_remove_devices_fn(struct device *dev, void *c)
> regulator_bulk_unregister_supply_alias(dev, cell->parent_supplies,
> cell->num_parent_supplies);
>
> - /* 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)
> {
> - atomic_t *cnts = NULL;
> -
> - device_for_each_child_reverse(parent, &cnts, mfd_remove_devices_fn);
> - kfree(cnts);
> + device_for_each_child_reverse(parent, NULL, mfd_remove_devices_fn);
> }
> EXPORT_SYMBOL(mfd_remove_devices);
>
> diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
> index bd8c0e089164..919f09fb07b7 100644
> --- a/include/linux/mfd/core.h
> +++ b/include/linux/mfd/core.h
> @@ -30,8 +30,6 @@ 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);
>
> --
> 2.17.1
>
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