linux-kernel - Re: [PATCH v4 2/4] RISC-V: Fix ioremap_cache() and ioremap

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Date:   Wed, 19 Oct 2022 21:40:56 +0530
From:   Anup Patel <apatel@...tanamicro.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mayuresh Chitale <mchitale@...tanamicro.com>
Subject: Re: [PATCH v4 2/4] RISC-V: Fix ioremap_cache() and ioremap_wc() for
 systems with Svpbmt

On Wed, Oct 19, 2022 at 7:49 PM Heiko Stuebner <heiko@...ech.de> wrote:
>
> Am Mittwoch, 19. Oktober 2022, 15:11:26 CEST schrieb Anup Patel:
> > Currently, all flavors of ioremap_xyz() function maps to the generic
> > ioremap() which means any ioremap_xyz() call will always map the
> > target memory as IO using _PAGE_IOREMAP page attributes. This breaks
> > ioremap_cache() and ioremap_wc() on systems with Svpbmt because memory
> > remapped using ioremap_cache() and ioremap_wc() will use _PAGE_IOREMAP
> > page attributes.
> >
> > To address above (just like other architectures), we implement RISC-V
> > specific ioremap_cache() and ioremap_wc() which maps memory using page
> > attributes as defined by the Svpbmt specification.
> >
> > Fixes: ff689fd21cb1 ("riscv: add RISC-V Svpbmt extension support")
> > Co-developed-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> > Signed-off-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
>
> Wasn't there discussion around those functions in general in v2?

Yes, there was discussion about a few drivers using ioremap_xyz()
which is discouraged and drivers should use memremap().

We still need the arch specific ioremap_xyz() functions/macros
added by this patch because these are required by the generic
kernel memremap() implementation (refer, kernel/iomem.c).

>
> In any case, the patch doesn't break anything on qemu and d1, so
>
> Tested-by: Heiko Stuebner <heiko@...ech.de>

Regards,
Anup

>
>
> > ---
> >  arch/riscv/include/asm/io.h      | 10 ++++++++++
> >  arch/riscv/include/asm/pgtable.h |  2 ++
> >  2 files changed, 12 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
> > index 92080a227937..92a31e543388 100644
> > --- a/arch/riscv/include/asm/io.h
> > +++ b/arch/riscv/include/asm/io.h
> > @@ -133,6 +133,16 @@ __io_writes_outs(outs, u64, q, __io_pbr(), __io_paw())
> >  #define outsq(addr, buffer, count) __outsq(PCI_IOBASE + (addr), buffer, count)
> >  #endif
> >
> > +#ifdef CONFIG_MMU
> > +#define ioremap_wc(addr, size)               \
> > +     ioremap_prot((addr), (size), _PAGE_IOREMAP_WC)
> > +#endif
> > +
> >  #include <asm-generic/io.h>
> >
> > +#ifdef CONFIG_MMU
> > +#define ioremap_cache(addr, size)    \
> > +     ioremap_prot((addr), (size), _PAGE_KERNEL)
> > +#endif
> > +
> >  #endif /* _ASM_RISCV_IO_H */
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 7ec936910a96..346b7c1a3eeb 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -182,6 +182,8 @@ extern struct pt_alloc_ops pt_ops __initdata;
> >  #define PAGE_TABLE           __pgprot(_PAGE_TABLE)
> >
> >  #define _PAGE_IOREMAP        ((_PAGE_KERNEL & ~_PAGE_MTMASK) | _PAGE_IO)
> > +#define _PAGE_IOREMAP_WC     ((_PAGE_KERNEL & ~_PAGE_MTMASK) | \
> > +                              _PAGE_NOCACHE)
> >  #define PAGE_KERNEL_IO               __pgprot(_PAGE_IOREMAP)
> >
> >  extern pgd_t swapper_pg_dir[];
> >
>
>
>
>