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

Jean-Christophe PLAGNIOL-VILLARD
2012-10-15T14:58:55Z

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

Best Regards,
J.