| Message ID | 20180323081857.57138-3-icenowy@aosc.io |
|---|---|
| State | Changes Requested |
| Delegated to: | Jagannadha Sutradharudu Teki |
| Headers | show |
| Series | Add 3GiB DRAM support to 64-bit Allwinner SoCs | expand |
On Fri, Mar 23, 2018 at 04:18:53PM +0800, Icenowy Zheng wrote: > Allwinner 64-bit SoCs can use 4GiB DRAM chip, however their memory map > has only allocated 3GiB for DRAM, so only 3GiB of the DRAM is > accessible. How would that work in Linux? > Add a Kconfig option for the maximum accessible DRAM. > > For A80 it should be a much higher value (8GiB), but as I have no A80 > device to test and originally U-Boot only supports 2GiB DRAM on A80, it > currently still falls under the 2GiB situation. I guess we have LPAE on armv7 to deal with this nicely. Maxime
On Fri, Mar 23, 2018 at 5:39 PM, Maxime Ripard <maxime.ripard@bootlin.com> wrote: > On Fri, Mar 23, 2018 at 04:18:53PM +0800, Icenowy Zheng wrote: >> Allwinner 64-bit SoCs can use 4GiB DRAM chip, however their memory map >> has only allocated 3GiB for DRAM, so only 3GiB of the DRAM is >> accessible. > > How would that work in Linux? > >> Add a Kconfig option for the maximum accessible DRAM. >> >> For A80 it should be a much higher value (8GiB), but as I have no A80 >> device to test and originally U-Boot only supports 2GiB DRAM on A80, it >> currently still falls under the 2GiB situation. > > I guess we have LPAE on armv7 to deal with this nicely. AFAIK even though we do have LPAE, the hardware bus is not wired up to take advantage of it. :( ChenYu
于 2018年3月23日 GMT+08:00 下午5:39:25, Maxime Ripard <maxime.ripard@bootlin.com> 写到: >On Fri, Mar 23, 2018 at 04:18:53PM +0800, Icenowy Zheng wrote: >> Allwinner 64-bit SoCs can use 4GiB DRAM chip, however their memory >map >> has only allocated 3GiB for DRAM, so only 3GiB of the DRAM is >> accessible. > >How would that work in Linux? From CPU's view only 3GiB DRAM is attached, so Linux can use the 3GiB space only. Only the DRAM controller knows that 4GiB DRAM is connected :-) > >> Add a Kconfig option for the maximum accessible DRAM. >> >> For A80 it should be a much higher value (8GiB), but as I have no A80 >> device to test and originally U-Boot only supports 2GiB DRAM on A80, >it >> currently still falls under the 2GiB situation. > >I guess we have LPAE on armv7 to deal with this nicely. > >Maxime
diff --git a/arch/arm/mach-sunxi/Kconfig b/arch/arm/mach-sunxi/Kconfig index b868f0e350..029821c82d 100644 --- a/arch/arm/mach-sunxi/Kconfig +++ b/arch/arm/mach-sunxi/Kconfig @@ -130,6 +130,13 @@ config MACH_SUNXI_H3_H5 select SUNXI_GEN_SUN6I select SUPPORT_SPL +# TODO: try out A80's 8GiB DRAM space +config SUNXI_DRAM_MAX_SIZE + hex + default 0xC0000000 if MACH_SUN50I + default 0xC0000000 if MACH_SUN50I_H5 + default 0x80000000 + choice prompt "Sunxi SoC Variant" optional
Allwinner 64-bit SoCs can use 4GiB DRAM chip, however their memory map has only allocated 3GiB for DRAM, so only 3GiB of the DRAM is accessible. Add a Kconfig option for the maximum accessible DRAM. For A80 it should be a much higher value (8GiB), but as I have no A80 device to test and originally U-Boot only supports 2GiB DRAM on A80, it currently still falls under the 2GiB situation. Signed-off-by: Icenowy Zheng <icenowy@aosc.io> --- No changes in v2. arch/arm/mach-sunxi/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+)