Hi Vincent,
Thank you for the patch.
On Tue, Mar 31, 2020 at 04:16:29PM +0200, Vincent Whitchurch wrote:
> If adv7511's devm_clk_get() for the cec clock returns -EPROBE_DEFER, we
> end up in an infinite probe loop. This happens:
>
> (1) adv7511's probe is called.
>
> (2) adv7511's probe adds some secondary i2c devices which bind to the
> dummy driver and thus call driver_deferred_probe_trigger() and
> increment deferred_trigger_count (see driver_bound()).
>
> (3) adv7511's probe returns -EPROBE_DEFER, and since the
> deferred_trigger_count has changed during the probe call,
> driver_deferred_probe_trigger() is called immediately (see
> really_probe()) and adv7511's probe is scheduled.
>
> (4) Goto step 1.
Lovely :-S
> [ 61.972915] really_probe: bus: 'i2c': really_probe: probing driver adv7511
> with device 0-0039
> [ 61.992734] really_probe: bus: 'i2c': really_probe: probing driver dummy
> with device 0-003f
> [ 61.993343] driver_bound: driver: 'dummy': driver_bound: bound to device
> '0-003f'
> [ 61.993626] really_probe: bus: 'i2c': really_probe: bound device 0-003f to
> driver dummy
> [ 61.995604] really_probe: bus: 'i2c': really_probe: probing driver dummy
> with device 0-0038
> [ 61.996381] driver_bound: driver: 'dummy': driver_bound: bound to device
> '0-0038'
> [ 61.996663] really_probe: bus: 'i2c': really_probe: bound device 0-0038 to
> driver dummy
> [ 61.998651] really_probe: bus: 'i2c': really_probe: probing driver dummy
> with device 0-003c
> [ 61.999222] driver_bound: driver: 'dummy': driver_bound: bound to device
> '0-003c'
> [ 61.999496] really_probe: bus: 'i2c': really_probe: bound device 0-003c to
> driver dummy
> [ 62.010050] really_probe: i2c 0-0039: Driver adv7511 requests probe
> deferral
> [ 62.011380] really_probe: bus: 'platform': really_probe: probing driver
> pwm-clock with device clock-cec
> [ 62.012812] really_probe: platform clock-cec: Driver pwm-clock requests
> probe deferral
> [ 62.024679] really_probe: bus: 'i2c': really_probe: probing driver adv7511
> with device 0-0039
>
> Fix this by calling devm_clk_get() before registering the secondary
> devices.
>
> Signed-off-by: Vincent Whitchurch
> ---
> drivers/gpu/drm/bridge/adv7511/adv7511_cec.c | 30 +++-
> drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 11 +--
> 2 files changed, 20 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> index a20a45c0b353..4b0fee32be21 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> @@ -286,28 +286,17 @@ static const struct cec_adap_ops adv7511_cec_adap_ops =
> {
> .adap_transmit = adv7511_cec_adap_transmit,
> };
>
> -static int adv7511_cec_parse_dt(struct device *dev, struct adv7511 *adv7511)
> -{
> - adv7511->cec_clk = devm_clk_get(dev, "cec");
> - if (IS_ERR(adv7511->cec_clk)) {
> - int ret = PTR_ERR(adv7511->cec_clk);
> -
> - adv7511->cec_clk = NULL;
> - return ret;
> - }
> - clk_prepare_enable(adv7511->cec_clk);
> - adv7511->cec_clk_freq = clk_get_rate(adv7511->cec_clk);
> - return 0;
> -}
> -
> int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511)
> {
> unsigned int offset = adv7511->type == ADV7533 ?
> ADV7533_REG_CEC_OFFSET : 0;
> - int ret = adv7511_cec_parse_dt(dev, adv7511);
> + int ret;
>
> - if (ret)
> - goto err_cec_parse_dt;
> + if (!adv7511->cec_clk)
> + goto err_cec_no_clock;
> +
> + clk_prepare_enable(adv7511->cec_clk);
> + adv7511->cec_clk_freq = clk_get_rate(adv7511->cec_clk);
>
> adv7511->cec_adap = cec_allocate_adapter(_cec_adap_ops,
> adv7511, dev_name(dev), CEC_CAP_DEFAULTS, ADV7511_MAX_ADDRS);
> @@ -342,8 +331,11 @@ int adv7511_cec_init(struct device *dev, struct adv7511
> *adv7511)
> err_cec_alloc:
> dev_info(dev, "Initializing CEC failed with error %d, disabling CEC\n",
>ret);
> -err_cec_parse_dt:
> + clk_disable_unprepare(adv7511->cec_clk);
> + /* Ensure that adv7511_remove() doesn't attempt to disable it again. */
Would it make sense to call devm_clk_put() here to already release the
clock ? Apart from that,
Reviewed-by: Laurent Pinchart
> + adv7511->cec_clk = NULL;
> +err_cec_no_clock:
> regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
>ADV7511_CEC_CTRL_POWER_DOWN);
> - return ret == -EPROBE_DEFER ? ret : 0;
> + return 0;
> }
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index 9e13e466e72c..ebc548e23ece 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1122,6 +1122,15 @@ static int adv7511_probe(struct
