Re: [PATCH] media: cec-notifier: debounce reporing of invalid phys addr

From: Hans Verkuil
Date: Mon Sep 02 2019 - 07:34:05 EST

Hi Jonas,

On 9/1/19 9:45 PM, Jonas Karlman wrote:
> When EDID is refreshed, HDMI cable is unplugged/replugged or
> an AVR is power cycled the CEC phys addr gets invalidated.
>
> This can cause some disruption of CEC communication when
> adapter is being reconfigured.
>
> Add a debounce option that can be used to debounce setting
> an invalid phys addr.

Debouncing can be dangerous since there are scenarios where there
is a quick unplug/replug such as in HDMI splitters.

So by default this should be off: I have yet to see issues with
just assuming the sink was unplugged and a potentially different
sink was plugged in.

That said, it would be nice to have a debounce module option, but
this doesn't belong in cec-notifier. Instead, this should be done
in the cec_s_phys_addr() function itself.

Regards,

Hans

>
> Power off AVR (debounce = 0):
> [ 101.536866] cec-dw_hdmi: new physical address f.f.f.f
> [ 102.495686] cec-dw_hdmi: new physical address 2.1.0.0
> [ 102.495913] cec-dw_hdmi: physical address: 2.1.0.0, claim 1 logical addresses
> [ 102.628574] cec-dw_hdmi: config: la 1 pa 2.1.0.0
> [ 105.130115] cec-dw_hdmi: new physical address f.f.f.f
> [ 106.979705] cec-dw_hdmi: new physical address 2.1.0.0
> [ 106.979872] cec-dw_hdmi: physical address: 2.1.0.0, claim 1 logical addresses
> [ 107.112399] cec-dw_hdmi: config: la 1 pa 2.1.0.0
> [ 108.979408] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 5
> [ 109.205386] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 11
>
> Power on AVR (debounce = 0):
> [ 158.398447] cec-dw_hdmi: new physical address f.f.f.f
> [ 161.977714] cec-dw_hdmi: new physical address 2.1.0.0
> [ 161.978766] cec-dw_hdmi: physical address: 2.1.0.0, claim 1 logical addresses
> [ 162.115624] cec-dw_hdmi: config: la 1 pa 2.1.0.0
> [ 162.402750] cec-dw_hdmi: new physical address f.f.f.f
> [ 162.403389] cec-dw_hdmi: cec_transmit_msg_fh: adapter is unconfigured
> [ 162.886757] cec-dw_hdmi: new physical address 2.1.0.0
> [ 162.886964] cec-dw_hdmi: physical address: 2.1.0.0, claim 1 logical addresses
> [ 163.510725] cec-dw_hdmi: config: la 1 pa 2.1.0.0
> [ 173.034200] cec-dw_hdmi: message 10 89 02 05 timed out
>
> Power off AVR (debounce = 5000):
> [ 251.720471] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 5
> [ 251.922432] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 11
>
> Power on AVR (debounce = 5000):
> [ 291.154262] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 5
> [ 291.296199] cec-dw_hdmi: reported physical address 2.0.0.0 for logical address 11
>
> Using a debounce of 5000 ms reconfiguring can be avoided.
>
> Signed-off-by: Jonas Karlman <jonas@xxxxxxxxx>
> ---
> drivers/media/cec/cec-core.c | 4 ++++
> drivers/media/cec/cec-notifier.c | 23 ++++++++++++++++++++++-
> drivers/media/cec/cec-priv.h | 1 +
> 3 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/cec/cec-core.c b/drivers/media/cec/cec-core.c
> index 9c610e1e99b8..c5094fd9b664 100644
> --- a/drivers/media/cec/cec-core.c
> +++ b/drivers/media/cec/cec-core.c
> @@ -28,6 +28,10 @@ static bool debug_phys_addr;
> module_param(debug_phys_addr, bool, 0644);
> MODULE_PARM_DESC(debug_phys_addr, "add CEC_CAP_PHYS_ADDR if set");
>
> +int cec_debounce;
> +module_param_named(debounce, cec_debounce, int, 0644);
> +MODULE_PARM_DESC(debounce, "debounce invalid phys addr");
> +
> static dev_t cec_dev_t;
>
> /* Active devices */
> diff --git a/drivers/media/cec/cec-notifier.c b/drivers/media/cec/cec-notifier.c
> index 4d82a5522072..0157d468cfe4 100644
> --- a/drivers/media/cec/cec-notifier.c
> +++ b/drivers/media/cec/cec-notifier.c
> @@ -12,11 +12,14 @@
> #include <linux/list.h>
> #include <linux/kref.h>
> #include <linux/of_platform.h>
> +#include <linux/workqueue.h>
>
> #include <media/cec.h>
> #include <media/cec-notifier.h>
> #include <drm/drm_edid.h>
>
> +#include "cec-priv.h"
> +
> struct cec_notifier {
> struct mutex lock;
> struct list_head head;
> @@ -28,11 +31,25 @@ struct cec_notifier {
> void (*callback)(struct cec_adapter *adap, u16 pa);
>
> u16 phys_addr;
> + struct delayed_work work;
> };
>
> static LIST_HEAD(cec_notifiers);
> static DEFINE_MUTEX(cec_notifiers_lock);
>
> +static void cec_notifier_delayed_work(struct work_struct *work)
> +{
> + struct cec_notifier *n =
> + container_of(to_delayed_work(work), struct cec_notifier, work);
> +
> + mutex_lock(&n->lock);
> + if (n->callback)
> + n->callback(n->cec_adap, n->phys_addr);
> + else if (n->cec_adap)
> + cec_s_phys_addr(n->cec_adap, n->phys_addr, false);
> + mutex_unlock(&n->lock);
> +}
> +
> struct cec_notifier *
> cec_notifier_get_conn(struct device *hdmi_dev, const char *conn_name)
> {
> @@ -62,6 +79,7 @@ cec_notifier_get_conn(struct device *hdmi_dev, const char *conn_name)
> }
> n->phys_addr = CEC_PHYS_ADDR_INVALID;
>
> + INIT_DELAYED_WORK(&n->work, cec_notifier_delayed_work);
> mutex_init(&n->lock);
> kref_init(&n->kref);
> list_add_tail(&n->head, &cec_notifiers);
> @@ -172,9 +190,12 @@ void cec_notifier_set_phys_addr(struct cec_notifier *n, u16 pa)
> if (n == NULL)
> return;
>
> + cancel_delayed_work_sync(&n->work);
> mutex_lock(&n->lock);
> n->phys_addr = pa;
> - if (n->callback)
> + if (cec_debounce > 0 && pa == CEC_PHYS_ADDR_INVALID)
> + schedule_delayed_work(&n->work, msecs_to_jiffies(cec_debounce));
> + else if (n->callback)
> n->callback(n->cec_adap, n->phys_addr);
> else if (n->cec_adap)
> cec_s_phys_addr(n->cec_adap, n->phys_addr, false);
> diff --git a/drivers/media/cec/cec-priv.h b/drivers/media/cec/cec-priv.h
> index 7bdf855aaecd..65176294fcf0 100644
> --- a/drivers/media/cec/cec-priv.h
> +++ b/drivers/media/cec/cec-priv.h
> @@ -27,6 +27,7 @@ static inline bool msg_is_raw(const struct cec_msg *msg)
>
> /* cec-core.c */
> extern int cec_debug;
> +extern int cec_debounce;
> int cec_get_device(struct cec_devnode *devnode);
> void cec_put_device(struct cec_devnode *devnode);
>
>