Re: [PATCH] MMC: fix sdhci-dove removal

Russell King - ARM Linux
2012-10-15T15:07:12Z

On Mon, Oct 15, 2012 at 04:58:55PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 11:44 Mon 15 Oct , Russell King - ARM Linux wrote:
> > 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@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@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@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);
> you have devm_clk_get too
>
> maybe you could use it here too

This isn't a cleanup patch, this is a patch just to fix some stupid bugs
in this code. If someone wants to convert that afterwards, it should be
an entirely separate patch.