linux-kernel - [PATCH v3] usb: typec: qcom-pmic-typec: split HPD bridge alloc and registration

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Message-Id: <20240416-qc-pmic-typec-hpd-split-v3-1-fd071e3191a1@linaro.org>
Date: Tue, 16 Apr 2024 05:18:56 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>, 
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
 Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: 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>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: [PATCH v3] usb: typec: qcom-pmic-typec: split HPD bridge alloc and
 registration

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>
---
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 | 8 ++++++--
 1 file changed, 6 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 e48412cdcb0f..96b41efae318 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);
 
@@ -110,6 +110,10 @@ static int qcom_pmic_typec_probe(struct platform_device *pdev)
 	if (ret)
 		goto fwnode_remove;
 
+	ret = devm_drm_dp_hpd_bridge_add(tcpm->dev, bridge_dev);
+	if (ret)
+		goto fwnode_remove;
+
 	return 0;
 
 fwnode_remove:

---
base-commit: 6bd343537461b57f3efe5dfc5fc193a232dfef1e
change-id: 20240405-qc-pmic-typec-hpd-split-22804201902b

Best regards,
-- 
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>