linux-kernel - [PATCH v4] mux: mmio: use reg property when parent device is not a syscon

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Date:   Mon, 23 Oct 2023 11:26:59 -0500
From:   Andrew Davis <afd@...com>
To:     Peter Rosin <peda@...ntia.se>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>
CC:     <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Andrew Davis <afd@...com>
Subject: [PATCH v4] mux: mmio: use reg property when parent device is not a syscon

The DT binding for the reg-mux compatible states it can be used when the
"parent device of mux controller is not syscon device". It also allows
for a reg property. When the reg property is provided, use that to
identify the address space for this mux. If not provided fallback to
using the parent device as a regmap provider.

While here use dev_err_probe() in the error path to prevent printing
a message on probe defer which now can happen in extra ways.

Signed-off-by: Andrew Davis <afd@...com>
Reviewed-by: Nishanth Menon <nm@...com>
---

Changes from v3:
 - Check for probe defer

Changes from v2:
 - Rebased on v6.6-rc1

Changes from v1:
 - Flip logic as suggested in v1[0]

[0] https://lore.kernel.org/lkml/1c27d9d4-b1cc-c158-90f7-f7e47e02c424@ti.com/T/

 drivers/mux/mmio.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/mux/mmio.c b/drivers/mux/mmio.c
index fd1d121a584ba..07c99588ff999 100644
--- a/drivers/mux/mmio.c
+++ b/drivers/mux/mmio.c
@@ -44,14 +44,17 @@ static int mux_mmio_probe(struct platform_device *pdev)
 	int ret;
 	int i;
 
-	if (of_device_is_compatible(np, "mmio-mux"))
+	if (of_device_is_compatible(np, "mmio-mux")) {
 		regmap = syscon_node_to_regmap(np->parent);
-	else
-		regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV);
+	} else {
+		regmap = device_node_to_regmap(np);
+		/* Fallback to checking the parent node on any error other than probe defer */
+		if (IS_ERR(regmap) && regmap != ERR_PTR(-EPROBE_DEFER))
+			regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV);
+	}
 	if (IS_ERR(regmap)) {
 		ret = PTR_ERR(regmap);
-		dev_err(dev, "failed to get regmap: %d\n", ret);
-		return ret;
+		return dev_err_probe(dev, ret, "failed to get regmap\n");
 	}
 
 	ret = of_property_count_u32_elems(np, "mux-reg-masks");
-- 
2.39.2