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Date: Thu, 20 Oct 2022 13:08:54 +0530 From: Anup Patel <apatel@...tanamicro.com> To: Arnd Bergmann <arnd@...db.de> Cc: Heiko Stübner <heiko@...ech.de>, 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 Thu, Oct 20, 2022 at 2:20 AM Arnd Bergmann <arnd@...db.de> wrote: > > On Wed, Oct 19, 2022, at 18:10, Anup Patel wrote: > > 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). > > There is a difference between the strongly discouraged > ioremap_cache() that pretty much has no valid users, and > the ioremap_wt/ioremap_wc functions that are sometimes used > for mapping video framebuffer or similar. > > It should be sufficient to provide a arch_memremap_wb() > and no ioremap_cache() to make memremap() work correctly. > Okay, I will simplify this patch to only implement arch_memremap_wb(). This will make the MEMREMAP_WB flag to work correctly but other MEMREMAP_xyz flags will always use non-cacheable IO mappings. Regards, Anup
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