Review from myself, I sent this one out pretty quickly just to get some
conversation started.
In the subject if should be 'earlycon' no 'eralycon'.
On Fri, Sep 27, 2024 at 03:56:56PM +0100, Stafford Horne wrote:
> With commit 53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap
> code") it was commented that early ioremap was not used in OpenRISC. I
> acked this but was wrong. Earlycon now fails with the below trace:
..
>
> To fix this we could either implement early_ioremap or implement fixmap.
> In this patch we choose the later option of implementing basic fixmap
> support.
>
> While fixing this we also remove the old FIX_IOREMAP slots that were
> used by early ioremap code. That code was also removed by commit
> 53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap code") but
> these definitions were not cleaned up.
>
> Fixes: 53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap code")
> Signed-off-by: Stafford Horne <sho...@gmail.com>
> ---
> arch/openrisc/Kconfig | 3 +++
> arch/openrisc/include/asm/fixmap.h | 21 +++++-------------
> arch/openrisc/mm/init.c | 34 ++++++++++++++++++++++++++++++
> 3 files changed, 42 insertions(+), 16 deletions(-)
>
> diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
> index 69c0258700b2..3279ef457c57 100644
> --- a/arch/openrisc/Kconfig
> +++ b/arch/openrisc/Kconfig
> @@ -65,6 +65,9 @@ config STACKTRACE_SUPPORT
> config LOCKDEP_SUPPORT
> def_bool y
>
> +config FIX_EARLYCON_MEM
> + def_bool y
> +
> menu "Processor type and features"
>
> choice
> diff --git a/arch/openrisc/include/asm/fixmap.h
> b/arch/openrisc/include/asm/fixmap.h
> index ecdb98a5839f..aaa6a26a3e92 100644
> --- a/arch/openrisc/include/asm/fixmap.h
> +++ b/arch/openrisc/include/asm/fixmap.h
> @@ -26,29 +26,18 @@
> #include <linux/bug.h>
> #include <asm/page.h>
>
> -/*
> - * On OpenRISC we use these special fixed_addresses for doing ioremap
> - * early in the boot process before memory initialization is complete.
> - * This is used, in particular, by the early serial console code.
> - *
> - * It's not really 'fixmap', per se, but fits loosely into the same
> - * paradigm.
> - */
> enum fixed_addresses {
> - /*
> - * FIX_IOREMAP entries are useful for mapping physical address
> - * space before ioremap() is useable, e.g. really early in boot
> - * before kmalloc() is working.
> - */
> -#define FIX_N_IOREMAPS 32
> - FIX_IOREMAP_BEGIN,
> - FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
> + FIX_EARLYCON_MEM_BASE,
> __end_of_fixed_addresses
> };
>
> #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
> /* FIXADDR_BOTTOM might be a better name here... */
> #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
> +#define FIXMAP_PAGE_IO PAGE_KERNEL_NOCACHE
> +
> +extern void __set_fixmap(enum fixed_addresses idx,
> + phys_addr_t phys, pgprot_t flags);
>
> #include <asm-generic/fixmap.h>
>
> diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
> index 1dcd78c8f0e9..7397d18c95d7 100644
> --- a/arch/openrisc/mm/init.c
> +++ b/arch/openrisc/mm/init.c
> @@ -207,6 +207,40 @@ void __init mem_init(void)
> return;
> }
>
> +static int __init map_page(unsigned long va, phys_addr_t pa, int flags)
> +{
> + p4d_t *p4d;
> + pud_t *pud;
> + pmd_t *pd;
> + pte_t *pg;
> + int err = -ENOMEM;
> +
> + p4d = p4d_offset(pgd_offset_k(va), va);
> + pud = pud_offset(p4d, va);
> + pd = pmd_offset(pud, va);
> + pg = pte_alloc_kernel(pd, va);
> +
> + if (pg != NULL) {
> + err = 0;
> + set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT,
> + __pgprot(flags)));
We maybe need to do something like flush tlb here, but since this is only used
by earlycon and before any io access is made it may be ok.
> + }
> + return err;
> +}
> +
> +void __init __set_fixmap(enum fixed_addresses idx,
> + phys_addr_t phys, pgprot_t prot)
> +{
> + unsigned long address = __fix_to_virt(idx);
> +
> + if (idx >= __end_of_fixed_addresses) {
> + BUG();
> + return;
> + }
> +
> + map_page(address, phys, pgprot_val(prot));
> +}
> +
> static const pgprot_t protection_map[16] = {
> [VM_NONE] = PAGE_NONE,
> [VM_READ] = PAGE_READONLY_X,
> --
> 2.44.0
>
