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

[spanda-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org]

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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