Re: [PATCH v5 6/6] drm/bridge/sii8620: use micro-USB cable detection logic to detect MHL

[Andrzej Hajda <a.hajda@samsung.com>]

On 27.02.2018 12:08, Chanwoo Choi wrote:
> Hi,
>
> On 2018년 02월 27일 16:11, Andrzej Hajda wrote:
>> From: Maciej Purski <m.purski@samsung.com>
>>
>> Currently MHL chip must be turned on permanently to detect MHL cable. It
>> duplicates micro-USB controller's (MUIC) functionality and consumes
>> unnecessary power. Lets use extcon attached to MUIC to enable MHL chip
>> only if it detects MHL cable.
>>
>> Signed-off-by: Maciej Purski <m.purski@samsung.com>
>> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
>> ---
>> v5: updated extcon API
>>
>> This is rework of the patch by Maciej with following changes:
>> - use micro-USB port bindings to get extcon, instead of extcon property,
>> - fixed remove sequence,
>> - fixed extcon get state logic.
>>
>> Code finding extcon node is hacky IMO, I guess ultimately it should be done
>> via some framework (maybe even extcon), or at least via helper, I hope it
>> can stay as is until the proper solution will be merged.
>>
>> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
>> ---
>>  drivers/gpu/drm/bridge/sil-sii8620.c | 97 ++++++++++++++++++++++++++++++++++--
>>  1 file changed, 94 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/sil-sii8620.c b/drivers/gpu/drm/bridge/sil-sii8620.c
>> index 9e785b8e0ea2..62b0adabcac2 100644
>> --- a/drivers/gpu/drm/bridge/sil-sii8620.c
>> +++ b/drivers/gpu/drm/bridge/sil-sii8620.c
>> @@ -17,6 +17,7 @@
>>  
>>  #include <linux/clk.h>
>>  #include <linux/delay.h>
>> +#include <linux/extcon.h>
>>  #include <linux/gpio/consumer.h>
>>  #include <linux/i2c.h>
>>  #include <linux/interrupt.h>
>> @@ -25,6 +26,7 @@
>>  #include <linux/list.h>
>>  #include <linux/module.h>
>>  #include <linux/mutex.h>
>> +#include <linux/of_graph.h>
>>  #include <linux/regulator/consumer.h>
>>  #include <linux/slab.h>
>>  
>> @@ -81,6 +83,10 @@ struct sii8620 {
>>  	struct edid *edid;
>>  	unsigned int gen2_write_burst:1;
>>  	enum sii8620_mt_state mt_state;
>> +	struct extcon_dev *extcon;
>> +	struct notifier_block extcon_nb;
>> +	struct work_struct extcon_wq;
>> +	int cable_state;
>>  	struct list_head mt_queue;
>>  	struct {
>>  		int r_size;
>> @@ -2175,6 +2181,77 @@ static void sii8620_init_rcp_input_dev(struct sii8620 *ctx)
>>  	ctx->rc_dev = rc_dev;
>>  }
>>  
>> +static void sii8620_cable_out(struct sii8620 *ctx)
>> +{
>> +	disable_irq(to_i2c_client(ctx->dev)->irq);
>> +	sii8620_hw_off(ctx);
>> +}
>> +
>> +static void sii8620_extcon_work(struct work_struct *work)
>> +{
>> +	struct sii8620 *ctx =
>> +		container_of(work, struct sii8620, extcon_wq);
>> +	int state = extcon_get_state(ctx->extcon, EXTCON_DISP_MHL);
>> +
>> +	if (state == ctx->cable_state)
>> +		return;
>> +
>> +	ctx->cable_state = state;
>> +
>> +	if (state > 0)
>> +		sii8620_cable_in(ctx);
>> +	else
>> +		sii8620_cable_out(ctx);
>> +}
>> +
>> +static int sii8620_extcon_notifier(struct notifier_block *self,
>> +			unsigned long event, void *ptr)
>> +{
>> +	struct sii8620 *ctx =
>> +		container_of(self, struct sii8620, extcon_nb);
>> +
>> +	schedule_work(&ctx->extcon_wq);
>> +
>> +	return NOTIFY_DONE;
>> +}
>> +
>> +static int sii8620_extcon_init(struct sii8620 *ctx)
>> +{
>> +	struct extcon_dev *edev;
>> +	struct device_node *musb, *muic;
>> +	int ret;
>> +
>> +	/* get micro-USB connector node */
>> +	musb = of_graph_get_remote_node(ctx->dev->of_node, 1, -1);
>> +	/* next get micro-USB Interface Controller node */
>> +	muic = of_get_next_parent(musb);
>> +
>> +	if (!muic) {
>> +		dev_info(ctx->dev, "no extcon found, switching to 'always on' mode\n");
>> +		return 0;
>> +	}
>> +
>> +	edev = extcon_find_edev_by_node(muic);
>> +	of_node_put(muic);
>> +	if (IS_ERR(edev)) {
>> +		if (PTR_ERR(edev) == -EPROBE_DEFER)
>> +			return -EPROBE_DEFER;
>> +		dev_err(ctx->dev, "Invalid or missing extcon\n");
>> +		return PTR_ERR(edev);
>> +	}
>> +
>> +	ctx->extcon = edev;
>> +	ctx->extcon_nb.notifier_call = sii8620_extcon_notifier;
>> +	INIT_WORK(&ctx->extcon_wq, sii8620_extcon_work);
>> +	ret = extcon_register_notifier(edev, EXTCON_DISP_MHL, &ctx->extcon_nb);
> You better to use devm_extcon_register_notifier().

With devm version I risk that in case of device unbind notification will
be called after .remove callback, it seems to me quite dangerous. Or am
I missing something?

Regards
Andrzej

>
>> +	if (ret) {
>> +		dev_err(ctx->dev, "failed to register notifier for MHL\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>  static inline struct sii8620 *bridge_to_sii8620(struct drm_bridge *bridge)
>>  {
>>  	return container_of(bridge, struct sii8620, bridge);
>> @@ -2307,13 +2384,20 @@ static int sii8620_probe(struct i2c_client *client,
>>  	if (ret)
>>  		return ret;
>>  
>> +	ret = sii8620_extcon_init(ctx);
>> +	if (ret < 0) {
>> +		dev_err(ctx->dev, "failed to initialize EXTCON\n");
>> +		return ret;
>> +	}
>> +
>>  	i2c_set_clientdata(client, ctx);
>>  
>>  	ctx->bridge.funcs = &sii8620_bridge_funcs;
>>  	ctx->bridge.of_node = dev->of_node;
>>  	drm_bridge_add(&ctx->bridge);
>>  
>> -	sii8620_cable_in(ctx);
>> +	if (!ctx->extcon)
>> +		sii8620_cable_in(ctx);
>>  
>>  	return 0;
>>  }
>> @@ -2322,8 +2406,15 @@ static int sii8620_remove(struct i2c_client *client)
>>  {
>>  	struct sii8620 *ctx = i2c_get_clientdata(client);
>>  
>> -	disable_irq(to_i2c_client(ctx->dev)->irq);
>> -	sii8620_hw_off(ctx);
>> +	if (ctx->extcon) {
>> +		extcon_unregister_notifier(ctx->extcon, EXTCON_DISP_MHL,
>> +					   &ctx->extcon_nb);
> Don't need to unregister the notifier if using devm_extcon_register_notifier().
>
>> +		flush_work(&ctx->extcon_wq);
>> +		if (ctx->cable_state > 0)
>> +			sii8620_cable_out(ctx);
>> +	} else {
>> +		sii8620_cable_out(ctx);
>> +	}
>>  	drm_bridge_remove(&ctx->bridge);
>>  
>>  	return 0;
>>
> If you use the resource managed function (devm_extcon_register_notifier), Looks good to me.
> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
>