linux-kernel - [PATCHv3] ARM: drivers/amba: release and cleanup the resource to allow for deferred probe

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Message-Id: <20191002143551.32288-1-dinguyen@kernel.org>
Date:   Wed,  2 Oct 2019 09:35:51 -0500
From:   Dinh Nguyen <dinguyen@...nel.org>
To:     linux@...linux.org.uk
Cc:     dinguyen@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
        p.zabel@...gutronix.de, thor.thayer@...ux.intel.com
Subject: [PATCHv3] ARM: drivers/amba: release and cleanup the resource to allow for deferred probe

With commit "79bdcb202a35 ARM: 8906/1: drivers/amba: add reset control to
amba bus probe", the amba bus driver needs to be deferred probe because the
reset driver is probed later. However with a deferred probe, the call to
request_resource() in the driver returns -EBUSY. The reason is the driver
has not released the resource from the previous probe attempt.

This patch fixes how we handle the condition of EPROBE_DEFER that is returned
from getting the reset controls. For this condition, the patch will jump
to defer_probe, which will iounmap, dev_pm_domain_detach, and release the
resource.

Fixes: 79bdcb202a35 ("ARM: 8906/1: drivers/amba: add reset control to
amba bus probe")
Signed-off-by: Dinh Nguyen <dinguyen@...nel.org>
---
v3: jump to defer_probe where the driver will unmap and pm_detach the
    driver resource for the next probe attempt
v2: release the resource when of_reset_control_array_get_optional_shared()
    returns EPROBE_DEFER
---
 drivers/amba/bus.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index f39f075abff9..4a021b1dab3d 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -409,9 +409,12 @@ static int amba_device_try_add(struct amba_device *dev, struct resource *parent)
 		 */
 		rstc = of_reset_control_array_get_optional_shared(dev->dev.of_node);
 		if (IS_ERR(rstc)) {
-			if (PTR_ERR(rstc) != -EPROBE_DEFER)
+			ret = PTR_ERR(rstc);
+			if (ret == -EPROBE_DEFER)
+				goto defer_probe;
+			else
 				dev_err(&dev->dev, "Can't get amba reset!\n");
-			return PTR_ERR(rstc);
+			return ret;
 		}
 		reset_control_deassert(rstc);
 		reset_control_put(rstc);
@@ -448,6 +451,7 @@ static int amba_device_try_add(struct amba_device *dev, struct resource *parent)
 			ret = -ENODEV;
 	}
 
+ defer_probe:
 	iounmap(tmp);
 	dev_pm_domain_detach(&dev->dev, true);
 
-- 
2.20.0