linux-kernel - Re: [PATCH v4] usb: typec: qcom-pmic-typec: split HPD bridge alloc and registration

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Date: Thu, 25 Apr 2024 12:53:29 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Caleb Connolly <caleb.connolly@...aro.org>
Subject: Re: [PATCH v4] usb: typec: qcom-pmic-typec: split HPD bridge alloc
 and registration

On Wed, Apr 24, 2024 at 05:16:57AM +0300, Dmitry Baryshkov wrote:
> If a probe function returns -EPROBE_DEFER after creating another device
> there is a change of ending up in a probe deferral loop, (see commit
> fbc35b45f9f6 ("Add documentation on meaning of -EPROBE_DEFER"). In case
> of the qcom-pmic-typec driver the tcpm_register_port() function looks up
> external resources (USB role switch and inherently via called
> typec_register_port() USB-C muxes, switches and retimers).
> 
> In order to prevent such probe-defer loops caused by qcom-pmic-typec
> driver, use the API added by Johan Hovold and move HPD bridge
> registration to the end of the probe function.
> 
> The devm_drm_dp_hpd_bridge_add() is called at the end of the probe
> function after all TCPM start functions. This is done as a way to
> overcome a different problem, the DRM subsystem can not properly cope
> with the DRM bridges being destroyed once the bridge is attached. Having
> this function call at the end of the probe function prevents possible
> DRM bridge device creation followed by destruction in case one of the
> TCPM start functions returns an error.
> 
> Reported-by: Caleb Connolly <caleb.connolly@...aro.org>
> Acked-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> Dependency: https://lore.kernel.org/lkml/20240418145730.4605-2-johan+linaro@kernel.org/
> ---
> Changes in v4:
> - Rebased on top of Johan's patches
> - Link to v3: https://lore.kernel.org/r/20240416-qc-pmic-typec-hpd-split-v3-1-fd071e3191a1@linaro.org
> 
> Changes in v3:
> - Updated commit message to explain my decisions (Johan).
> - Link to v2: https://lore.kernel.org/r/20240408-qc-pmic-typec-hpd-split-v2-1-1704f5321b73@linaro.org
> 
> Changes in v2:
> - Fix commit message (Bryan)
> - Link to v1: https://lore.kernel.org/r/20240405-qc-pmic-typec-hpd-split-v1-1-363daafb3c36@linaro.org
> ---
>  drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c b/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
> index d3958c061a97..501eddb294e4 100644
> --- a/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
> +++ b/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
> @@ -41,7 +41,7 @@ static int qcom_pmic_typec_probe(struct platform_device *pdev)
>  	struct device_node *np = dev->of_node;
>  	const struct pmic_typec_resources *res;
>  	struct regmap *regmap;
> -	struct device *bridge_dev;
> +	struct auxiliary_device *bridge_dev;
>  	u32 base;
>  	int ret;
>  
> @@ -92,7 +92,7 @@ static int qcom_pmic_typec_probe(struct platform_device *pdev)
>  	if (!tcpm->tcpc.fwnode)
>  		return -EINVAL;
>  
> -	bridge_dev = drm_dp_hpd_bridge_register(tcpm->dev, to_of_node(tcpm->tcpc.fwnode));
> +	bridge_dev = devm_drm_dp_hpd_bridge_alloc(tcpm->dev, to_of_node(tcpm->tcpc.fwnode));
>  	if (IS_ERR(bridge_dev))
>  		return PTR_ERR(bridge_dev);
>  
> @@ -110,8 +110,14 @@ static int qcom_pmic_typec_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto port_stop;
>  
> +	ret = devm_drm_dp_hpd_bridge_add(tcpm->dev, bridge_dev);
> +	if (ret)
> +		goto pdphy_stop;
> +
>  	return 0;
>  
> +pdphy_stop:
> +	tcpm->pdphy_stop(tcpm);
>  port_stop:
>  	tcpm->port_stop(tcpm);
>  port_unregister:
> 
> ---
> base-commit: 15d419fa23ecc51e388a369bbeaf3b47b0b5c76a
> change-id: 20240405-qc-pmic-typec-hpd-split-22804201902b
> 
> Best regards,
> -- 
> Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

-- 
heikki