[PATCH] MMC: fix sdhci-dove removal

[Russell King - ARM Linux]

On Mon, Oct 15, 2012 at 11:37:25AM +0100, Russell King - ARM Linux wrote:
> On Mon, Oct 15, 2012 at 10:43:48AM +0100, Russell King - ARM Linux wrote:
> > 1. Unregister the device _BEFORE_ taking away any resources it may
> >    be using.
> > 2. Don't check clks against NULL.
> > 
> > Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> 
> Looking at this driver some more, who the hell came up with the sdhci
> registration interface?  It violates one of the most fundamental
> principles of kernel driver programming.  You do _NOT_ publish your
> driver interfaces _UNTIL_ you have finished setting your device up.
> Otherwise, in a preemptible or SMP kernel, your driver can be used
> before the initialization has completed.
> 
> As this driver calls sdhci_pltfm_register() before it has obtained the
> clock for the interface, and this function does:
> 	sdhci_pltfm_init
> 	sdhci_add_host
> 		mmc_add_host
> 			mmc_start_host
> 				mmc_power_up
> 					mmc_set_ios
> 						sdhci_set_ios
> 
> See, we're trying to power up and clock the card _before_ the dove
> sdhci driver has even claimed the clock let alone enabled it.  This
> is total bollocks.  The sdhci platform interface is total crap for
> creating this broken design in the first place.  This is why MMC has
> the init + add interfaces, they're there to allow drivers to do stuff
> the Right(tm) way and avoid shit like the above.
> 
> This should have been picked up at review time before the driver went
> into mainline.  In any case, it needs to be fixed.

Here's an updated patch which just about fixes the sdhci-dove driver.
I would not be surprised given the idiotic sdhci-pltfm API if many
other drivers suffered the same bug.

8<====
From: Russell King <rmk+kernel at arm.linux.org.uk>
Subject: [PATCH] MMC: fix sdhci-dove probe/removal

1. Never ever publish a device in the system before it has been setup
   to a usable state.
2. Unregister the device _BEFORE_ taking away any resources it may be
   using.
3. Don't check clks against NULL.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/mmc/host/sdhci-dove.c |   36 ++++++++++++++++++------------------
 1 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/mmc/host/sdhci-dove.c b/drivers/mmc/host/sdhci-dove.c
index a6e53a1..7d3a4e4 100644
--- a/drivers/mmc/host/sdhci-dove.c
+++ b/drivers/mmc/host/sdhci-dove.c
@@ -83,30 +83,31 @@ static int __devinit sdhci_dove_probe(struct platform_device *pdev)
 	struct sdhci_dove_priv *priv;
 	int ret;
 
-	ret = sdhci_pltfm_register(pdev, &sdhci_dove_pdata);
-	if (ret)
-		goto sdhci_dove_register_fail;
-
 	priv = devm_kzalloc(&pdev->dev, sizeof(struct sdhci_dove_priv),
 			    GFP_KERNEL);
 	if (!priv) {
 		dev_err(&pdev->dev, "unable to allocate private data");
-		ret = -ENOMEM;
-		goto sdhci_dove_allocate_fail;
+		return -ENOMEM;
 	}
 
+	priv->clk = clk_get(&pdev->dev, NULL);
+	if (!IS_ERR(priv->clk))
+		clk_prepare_enable(priv->clk);
+
+	ret = sdhci_pltfm_register(pdev, &sdhci_dove_pdata);
+	if (ret)
+		goto sdhci_dove_register_fail;
+
 	host = platform_get_drvdata(pdev);
 	pltfm_host = sdhci_priv(host);
 	pltfm_host->priv = priv;
 
-	priv->clk = clk_get(&pdev->dev, NULL);
-	if (!IS_ERR(priv->clk))
-		clk_prepare_enable(priv->clk);
 	return 0;
 
-sdhci_dove_allocate_fail:
-	sdhci_pltfm_unregister(pdev);
 sdhci_dove_register_fail:
+	clk_unprepare_disable(priv->clk);
+	clk_put(priv->clk);
+sdhci_dove_allocate_fail:
 	return ret;
 }
 
@@ -116,14 +117,13 @@ static int __devexit sdhci_dove_remove(struct platform_device *pdev)
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct sdhci_dove_priv *priv = pltfm_host->priv;
 
-	if (priv->clk) {
-		if (!IS_ERR(priv->clk)) {
-			clk_disable_unprepare(priv->clk);
-			clk_put(priv->clk);
-		}
-		devm_kfree(&pdev->dev, priv->clk);
+	sdhci_pltfm_unregister(pdev);
+
+	if (!IS_ERR(priv->clk)) {
+		clk_disable_unprepare(priv->clk);
+		clk_put(priv->clk);
 	}
-	return sdhci_pltfm_unregister(pdev);
+	return 0;
 }
 
 static struct platform_driver sdhci_dove_driver = {
-- 
1.7.4.4