Subject: Re: [PATCH] powerpc/fsl_pci: Fix pci stack build bug with FRAME_WARN

From: Scott Wood <[email-masked]>
Date: Tue, 20 Jan 2015 18:31:32 -0600

On Tue, 2015-01-20 at 14:03 -0600, Kim Phillips wrote:
> Fix this:
> 
>   CC      arch/powerpc/sysdev/fsl_pci.o
> arch/powerpc/sysdev/fsl_pci.c: In function 'fsl_pcie_check_link':
> arch/powerpc/sysdev/fsl_pci.c:91:1: error: the frame size of 1360 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
> 
> when configuring FRAME_WARN, by converting the allocation from the
> stack to the heap.  We use GFP_ATOMIC since this function can be
> called with interrupts disabled.
> 
> Signed-off-by: Kim Phillips <[email-masked]>
> ---
>  arch/powerpc/sysdev/fsl_pci.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
> index 6455c1e..635d743 100644
> --- a/arch/powerpc/sysdev/fsl_pci.c
> +++ b/arch/powerpc/sysdev/fsl_pci.c
> @@ -69,11 +69,13 @@ static int fsl_pcie_check_link(struct pci_controller *hose)
>  
>  	if (hose->indirect_type & PPC_INDIRECT_TYPE_FSL_CFG_REG_LINK) {
>  		if (hose->ops->read == fsl_indirect_read_config) {
> -			struct pci_bus bus;
> -			bus.number = hose->first_busno;
> -			bus.sysdata = hose;
> -			bus.ops = hose->ops;
> -			indirect_read_config(&bus, 0, PCIE_LTSSM, 4, &val);
> +			struct pci_bus *bus;
> +			bus = kmalloc(sizeof(*bus), GFP_ATOMIC);
> +			bus->number = hose->first_busno;

Missing check for allocation failure.

Do we not have a real struct pci_bus we can use here?  Or refactor
indirect_read_config() to take hose and bus number instead?

If putting a pci_bus struct on the stack is no longer OK, then
fake_pci_bus() should be fixed as well.  I wonder if GCC is allocating
separate pci_bus structs on the stack for this one and the one that
early_read_config_dword() uses...

-Scott