[RFC PATCH 04/11] PCI: tegra: limit to MMU build only

On Tuesday, November 22, 2016 9:40:39 AM CET Vladimir Murzin wrote:

On 22/11/16 09:31, Arnd Bergmann wrote:

quoted

On Tuesday, November 22, 2016 9:26:01 AM CET Vladimir Murzin wrote:

quoted

This driver uses functionality which available for MMU build only,
thus add dependency on MMU.

Cc: Thierry Reding <redacted>
Signed-off-by: Vladimir Murzin <redacted>

Can you be more specific about what requires the MMU here?

Is it the I/O space remapping or something else?

Yes it comes from I/O space remapping.

The fill error log:

  CC      drivers/pci/host/pci-tegra.o
In file included from ./arch/arm/include/asm/page.h:22:0,
                 from ./arch/arm/include/asm/thread_info.h:17,
                 from ./include/linux/thread_info.h:58,
                 from ./include/asm-generic/current.h:4,
                 from ./arch/arm/include/generated/asm/current.h:1,
                 from ./include/linux/mutex.h:13,
                 from ./include/linux/notifier.h:13,
                 from ./include/linux/clk.h:17,
                 from drivers/pci/host/pci-tegra.c:29:
drivers/pci/host/pci-tegra.c: In function 'tegra_pcie_bus_alloc':
drivers/pci/host/pci-tegra.c:388:27: error: 'L_PTE_PRESENT' undeclared (first use in this function)
  pgprot_t prot = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |

That is not the I/O space, that is the config space.

Not sure what a better alternative would be, but the manual selection
of page flags makes the driver non-portable and dependent on architecture
specifics that it really shouldn't have to worry about.

In common PCI code, we use pgprot_device(PAGE_KERNEL)) at some point,
and that sounds like the right thing to do, but ARM doesn't provide
an override for it and the fallback is pgprot_noncached(), which is
probably wrong here.

Unless someone has a good idea for how to change the driver, just
mention this in the changelog.

	Arnd