> -----Original Message----- > From: Auer, Lukas [mailto:lukas.a...@aisec.fraunhofer.de] > Sent: Monday, January 21, 2019 1:35 AM > To: s...@chromium.org; bmeng...@gmail.com; r...@andestech.com; Anup > Patel <anup.pa...@wdc.com>; joe.hershber...@ni.com; > yamada.masah...@socionext.com > Cc: paul.walms...@sifive.com; pal...@sifive.com; h...@infradead.org; u- > b...@lists.denx.de; ag...@suse.de; Atish Patra <atish.pa...@wdc.com> > Subject: Re: [PATCH v2 03/11] riscv: generic: Ensure that U-Boot runs within > 4GB for 64bit systems > > On Fri, 2019-01-18 at 11:18 +0000, Anup Patel wrote: > > On 64bit systems, the DRAM top can be easily beyond 4GB and U-Boot > DMA > > mapping APIs will generate DMA addresses beyond 4GB. This breaks DMA > > programming in 32bit DMA capable devices (such as Cadence MACB > > ethernet). For example, If DRAM is more then 2GB on QEMU sifive_u > > machine then Cadence MACB ethernet stops working for U-Boot because > it > > is a 32bit DMA capable device. > > > > To handle 32bit DMA capable devices on 64bit systems, we provide > > custom implementation of board_get_usable_ram_top() which ensures > that > > usable ram top is not more then 4GB. This in-turn ensures that U-Boot > > always runs within 4GB hence DMA addresses generated by DMA mapping > > APIs will be within 4GB too. > > > > Signed-off-by: Atish Patra <atish.pa...@wdc.com> > > Signed-off-by: Anup Patel <anup.pa...@wdc.com> > > Reviewed-by: Alexander Graf <ag...@suse.de> > > --- > > arch/riscv/cpu/generic/dram.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > Reviewed-by: Lukas Auer <lukas.a...@aisec.fraunhofer.de> > > With one nit below. > > > diff --git a/arch/riscv/cpu/generic/dram.c > > b/arch/riscv/cpu/generic/dram.c index 84d87d2a7f..5725d3c7ae 100644 > > --- a/arch/riscv/cpu/generic/dram.c > > +++ b/arch/riscv/cpu/generic/dram.c > > @@ -5,6 +5,9 @@ > > > > #include <common.h> > > #include <fdtdec.h> > > +#include <linux/sizes.h> > > + > > +DECLARE_GLOBAL_DATA_PTR; > > > > int dram_init(void) > > { > > @@ -15,3 +18,20 @@ int dram_init_banksize(void) { > > return fdtdec_setup_memory_banksize(); } > > + > > +ulong board_get_usable_ram_top(ulong total_size) { #ifdef > > +CONFIG_64BIT > > + /* > > + * Ensure that we run from first 4GB so that all > > + * addresses used by U-Boot are 32bit addresses. > > + * > > + * This in-turn ensures that 32bit DMA capabale > > nit: capable
Sure, will update. > > > + * devices work fine because DMA mapping APIs will > > + * provide 32bit DMA addresses only. > > + */ > > + if (gd->ram_top > SZ_4G) > > + return SZ_4G; > > +#endif > > + return gd->ram_top; > > +} Regards, Anup _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
