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Message-ID: <54edf1d7-056f-ad75-4d94-e1efa2ffdc1c@samsung.com>
Date: Wed, 28 Feb 2018 14:44:05 +0100
From: Andrzej Hajda <a.hajda@...sung.com>
To: Chanwoo Choi <cw00.choi@...sung.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>
Cc: Maciej Purski <m.purski@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
dri-devel@...ts.freedesktop.org, Inki Dae <inki.dae@...sung.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Krzysztof Kozlowski <krzk@...nel.org>,
Archit Taneja <architt@...eaurora.org>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v5 6/6] drm/bridge/sii8620: use micro-USB cable
detection logic to detect MHL
On 27.02.2018 23:26, Chanwoo Choi wrote:
> Hi,
>
> On 2018년 02월 27일 21:05, Andrzej Hajda wrote:
>> On 27.02.2018 12:08, Chanwoo Choi wrote:
>>> Hi,
>>>
>>> On 2018년 02월 27일 16:11, Andrzej Hajda wrote:
>>>> From: Maciej Purski <m.purski@...sung.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@...sung.com>
>>>> Signed-off-by: Andrzej Hajda <a.hajda@...sung.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@...sung.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?
> If you use the cancel_work_sync() in remove() instead of flush_work(),
> you can use the 'devm_extcon_*'.
cancel_work_sync() does not prevent works scheduled later from execution
[1] and this scenario is possible with devm_extcon_register_notifier()
and cancel_work_sync().
So we end up with:
sii8620_remove() calls cancel_work_sync()
...
notifier(called asynchronously) schedules sii8620_extcon_work()
...
notifier is removed by devm framework
sii8620 context is destroyed by devm framework
...
sii8620_extcon_work is executed on destroyed context !!! BUG !!!
For me it seems that devm_extcon_register_notifier is not safe in this case.
[1]: Since documentation was not clear I have performed live test
confirming my suspicions.
Regards
Andrzej
>
>> 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@...sung.com>
>>>
>> --
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>
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