Re: [PATCH v5 1/4] drm/bridge: add support for sn65dsi86 bridge driver

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On 2018-05-08 03:50, Stephen Boyd wrote:
Quoting Sean Paul (2018-05-02 12:03:16)
On Wed, May 02, 2018 at 10:01:59AM +0530, Sandeep Panda wrote:

> +     struct drm_display_mode curr_mode;
> +     struct mutex lock;
> +     unsigned int ctrl_ref_count;
> +};
> +
> +static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
> +     { .range_min = 0, .range_max = 0xff },
> +};
> +
> +static const struct regmap_access_table ti_sn_bridge_volatile_table = {
> +     .yes_ranges = ti_sn_bridge_volatile_ranges,
> +     .n_yes_ranges = ARRAY_SIZE(ti_sn_bridge_volatile_ranges),
> +};
> +
> +static const struct regmap_config ti_sn_bridge_regmap_config = {
> +     .reg_bits = 8,
> +     .val_bits = 8,
> +     .volatile_table = &ti_sn_bridge_volatile_table,
> +     .cache_type = REGCACHE_NONE,
> +};
> +
> +static int ti_sn_bridge_power_ctrl(struct ti_sn_bridge *pdata, bool enable)
> +{
> +     int ret = 0;
> +
> +     mutex_lock(&pdata->lock);
> +     if (enable)
> +             pdata->ctrl_ref_count++;
> +     else
> +             pdata->ctrl_ref_count--;

I think you should use a kref instead of rolling your own ref_count. You can handle release by calling kref_put_mutex(), which will handle the reference and the lock. On the acquire side, you can use kref_get_unless_zero which will be
fast if the reference is already active.

Why not use runtime PM?

I think PM runtime will be a better approach since we are trying to protect bridge power source related resources here.
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