Subject: Re: [PATCH 10/13] powerpc: Add arch/powerpc mv64x60 PCI setup

From: Arnd Bergmann <[email-masked]>
Date: Thu, 3 May 2007 09:17:46 +0200

On Wednesday 02 May 2007, Dale Farnsworth wrote:

> Index: linux-2.6-powerpc-df/arch/powerpc/sysdev/Makefile
> ===================================================================
> --- linux-2.6-powerpc-df.orig/arch/powerpc/sysdev/Makefile
> +++ linux-2.6-powerpc-df/arch/powerpc/sysdev/Makefile
> @@ -16,6 +16,10 @@ obj-$(CONFIG_TSI108_BRIDGE)	+= tsi108_pc
>  obj-$(CONFIG_QUICC_ENGINE)	+= qe_lib/
>  obj-$(CONFIG_MV64X60)		+= mv64x60_pic.o mv64x60_dev.o
>  
> +ifeq ($(CONFIG_PCI),y)
> +obj-$(CONFIG_MV64X60)		+= mv64x60_pci.o
> +endif
> +

I'd write this as

mv64x60-$(CONFIG_INDIRECT_PCI)	+= mv64x60_pci.o
obj-$(CONFIG_MV64X60)		+= mv64x60-y

though that doesn't make much difference any more

> +#ifdef CONFIG_SYSFS
> +/* 32-bit hex or dec stringified number + '\n' */
> +#define MV64X60_VAL_LEN_MAX		11
> +#define MV64X60_PCICFG_CPCI_HOTSWAP	0x68
> +
> +DECLARE_MUTEX(mv64x60_hs_lock);

Please avoid using struct semephores in new code, we now have struct mutex
for this, which gets defined as

static DEFINE_MUTEX(mv64x60_hs_mutex);

> +static ssize_t mv64x60_hs_reg_read(struct kobject *kobj, char *buf, loff_t off,
> +				   size_t count)
> +{
> +	u32 v;
> +	int save_exclude;
> +
> +	if (off > 0)
> +		return 0;
> +	if (count < MV64X60_VAL_LEN_MAX)
> +		return -EINVAL;
> +
> +	if (down_interruptible(&mv64x60_hs_lock))
> +		return -ERESTARTSYS;
> +	save_exclude = mv64x60_pci_exclude_bridge;
> +	mv64x60_pci_exclude_bridge = 0;
> +	early_read_config_dword(mv64x60_primary_hose, 0, PCI_DEVFN(0, 0),
> +				MV64X60_PCICFG_CPCI_HOTSWAP, &v);

Why do you use early_read_config_dword, not pci_read_config_dword()?

> +	mv64x60_pci_exclude_bridge = save_exclude;
> +	up(&mv64x60_hs_lock);
> +
> +	return sprintf(buf, "0x%08x\n", v);
> +}

<snip>

> +static int mv64x60_exclude_device(u_char bus, u_char devfn)
> +{
> +       if ((bus == 0 || bus == mv64x60_pci2_busno) &&
> +           PCI_SLOT(devfn) == 0 && mv64x60_pci_exclude_bridge)
> +               return PCIBIOS_DEVICE_NOT_FOUND;
> +
> +       return PCIBIOS_SUCCESSFUL;
> +}

The locking here looks wrong. If you call mv64x60_exclude_device() from one thread
thread while another one is calling mv64x60_hs_reg_read(), the bridge will
not be excluded.

	Arnd <><