[PATCH v2 06/10] rpi4: add a mapping for the PCIe XHCI controller MMIO registers (ARM 32bit)

[Tom Rini]

On Fri, May 08, 2020 at 11:26:36PM +0200, Matthias Brugger wrote:
> Adding Tom as he is the arm maintainer.
> 
> On 04/05/2020 14:45, Sylwester Nawrocki wrote:
> > From: Marek Szyprowski <m.szyprowski at samsung.com>
> > 
> > Create a non-cacheable mapping for the 0x600000000 physical memory region,
> > where MMIO registers for the PCIe XHCI controller are instantiated by the
> > PCIe bridge. Due to 32bit limit in the CPU virtual address space in ARM
> > 32bit mode, this region is mapped at 0xff800000 CPU virtual address.
> > 
> > Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> > Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com>
> > ---
> > Changes since v1:
> >  - none.
> > ---
> >  arch/arm/mach-bcm283x/Kconfig             |  1 +
> >  arch/arm/mach-bcm283x/include/mach/base.h |  7 +++++
> >  arch/arm/mach-bcm283x/init.c              | 52 +++++++++++++++++++++++++++++++
> >  3 files changed, 60 insertions(+)
> > 
> > diff --git a/arch/arm/mach-bcm283x/Kconfig b/arch/arm/mach-bcm283x/Kconfig
> > index 00419bf..bcb7f1d 100644
> > --- a/arch/arm/mach-bcm283x/Kconfig
> > +++ b/arch/arm/mach-bcm283x/Kconfig
> > @@ -36,6 +36,7 @@ config BCM2711_32B
> >  	select BCM2711
> >  	select ARMV7_LPAE
> >  	select CPU_V7A
> > +	select PHYS_64BIT
> >  
> >  config BCM2711_64B
> >  	bool "Broadcom BCM2711 SoC 64-bit support"
> > diff --git a/arch/arm/mach-bcm283x/include/mach/base.h b/arch/arm/mach-bcm283x/include/mach/base.h
> > index c4ae398..1d10dc9 100644
> > --- a/arch/arm/mach-bcm283x/include/mach/base.h
> > +++ b/arch/arm/mach-bcm283x/include/mach/base.h
> > @@ -6,6 +6,13 @@
> >  #ifndef _BCM283x_BASE_H_
> >  #define _BCM283x_BASE_H_
> >  
> > +#include <linux/types.h>
> > +
> >  extern unsigned long rpi_bcm283x_base;
> >  
> > +#ifdef CONFIG_ARMV7_LPAE
> > +extern void *rpi4_phys_to_virt(phys_addr_t paddr);
> > +#define phys_to_virt(x) rpi4_phys_to_virt(x)
> > +#endif
> > +
> >  #endif
> > diff --git a/arch/arm/mach-bcm283x/init.c b/arch/arm/mach-bcm283x/init.c
> > index 6a748da..5d0d160 100644
> > --- a/arch/arm/mach-bcm283x/init.c
> > +++ b/arch/arm/mach-bcm283x/init.c
> > @@ -145,6 +145,58 @@ int mach_cpu_init(void)
> >  }
> >  
> >  #ifdef CONFIG_ARMV7_LPAE
> > +
> > +#define BCM2711_RPI4_PCIE_XHCI_MMIO_VIRT	0xff800000UL
> > +
> > +void *rpi4_phys_to_virt(phys_addr_t paddr)
> > +{
> > +	if (paddr >= BCM2711_RPI4_PCIE_XHCI_MMIO_PHYS)
> > +		paddr = paddr - BCM2711_RPI4_PCIE_XHCI_MMIO_PHYS +
> > +			BCM2711_RPI4_PCIE_XHCI_MMIO_VIRT;
> > +	return (void *)(unsigned long)paddr;
> 
> I think for this cases we have addrmap_phys_to_virt() which up to now is only
> used by powerpc.
> 
> > +}
> > +
> > +static void set_section_phys(unsigned int section, phys_addr_t phys,
> > +			     enum dcache_option option)
> > +{
> > +	u64 *page_table = (u64 *)gd->arch.tlb_addr;
> > +	/* Need to set the access flag to not fault */
> > +	u64 value = TTB_SECT_AP | TTB_SECT_AF;
> > +
> > +	/* Add the page offset */
> > +	value |= (phys);
> > +
> > +	/* Add caching bits */
> > +	value |= option;
> > +
> > +	/* Set PTE */
> > +	page_table[section] = value;
> > +}
> > +
> > +static void rpi4_create_pcie_xhci_mapping(void)
> > +{
> > +	unsigned sect = BCM2711_RPI4_PCIE_XHCI_MMIO_VIRT >> MMU_SECTION_SHIFT;
> > +	phys_addr_t phys_addr = BCM2711_RPI4_PCIE_XHCI_MMIO_PHYS;
> > +	unsigned int size = BCM2711_RPI4_PCIE_XHCI_MMIO_SIZE;
> > +
> > +	while (size) {
> > +		set_section_phys(sect, phys_addr, DCACHE_OFF);
> > +		sect++;
> > +		phys_addr += MMU_SECTION_SIZE;
> > +		size -= MMU_SECTION_SIZE;
> > +	}
> > +}
> 
> I wonder if we can't do all this in the pcie driver probe function. Maybe we can
> create a new function like mmu_set_region_dcache_behaviour_phys which allows us
> to update a mapping that's not 1:1.
> 
> Tom what do you think?

I think a harder look at how PowerPC handled this situation is in order,
and then following / extending that path is in order.

-- 
Tom
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