linux-kernel - [PATCH] mfd: ab8500-sysctrl: Handle probe deferral

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Message-Id: <20170113095355.5406-1-linus.walleij@linaro.org>
Date:   Fri, 13 Jan 2017 10:53:55 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     lee.jones@...aro.org, linux-kernel@...r.kernel.org
Cc:     Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH] mfd: ab8500-sysctrl: Handle probe deferral

In the current boot, clients making use of the AB8500 sysctrl
may be probed before the ab8500-sysctrl driver. This gives them
-EINVAL, but should rather give -EPROBE_DEFER.

Before this, the abx500 clock driver didn't probe properly,
and as a result the codec driver in turn using the clocks did
not probe properly. After this patch, everything probes
properly.

Also add OF compatible-string probing. This driver is all
device tree, so let's just make a drive-by-fix of that as
well.

Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
 drivers/mfd/ab8500-sysctrl.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/mfd/ab8500-sysctrl.c b/drivers/mfd/ab8500-sysctrl.c
index 80c0efa66ac1..5b0a0850ef69 100644
--- a/drivers/mfd/ab8500-sysctrl.c
+++ b/drivers/mfd/ab8500-sysctrl.c
@@ -101,7 +101,7 @@ int ab8500_sysctrl_read(u16 reg, u8 *value)
 	u8 bank;
 
 	if (sysctrl_dev == NULL)
-		return -EINVAL;
+		return -EPROBE_DEFER;
 
 	bank = (reg >> 8);
 	if (!valid_bank(bank))
@@ -117,11 +117,13 @@ int ab8500_sysctrl_write(u16 reg, u8 mask, u8 value)
 	u8 bank;
 
 	if (sysctrl_dev == NULL)
-		return -EINVAL;
+		return -EPROBE_DEFER;
 
 	bank = (reg >> 8);
-	if (!valid_bank(bank))
+	if (!valid_bank(bank)) {
+		pr_err("invalid bank\n");
 		return -EINVAL;
+	}
 
 	return abx500_mask_and_set_register_interruptible(sysctrl_dev, bank,
 		(u8)(reg & 0xFF), mask, value);
@@ -148,9 +150,15 @@ static int ab8500_sysctrl_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static const struct of_device_id ab8500_sysctrl_match[] = {
+	{ .compatible = "stericsson,ab8500-sysctrl", },
+	{}
+};
+
 static struct platform_driver ab8500_sysctrl_driver = {
 	.driver = {
 		.name = "ab8500-sysctrl",
+		.of_match_table = ab8500_sysctrl_match,
 	},
 	.probe = ab8500_sysctrl_probe,
 	.remove = ab8500_sysctrl_remove,
-- 
2.9.3