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Date: Wed, 14 Nov 2018 16:38:24 +0100
From: Christoph Hellwig <hch@....de>
To: "Maciej W. Rozycki" <macro@...ux-mips.org>
Cc: Ralf Baechle <ralf@...ux-mips.org>,
Paul Burton <paul.burton@...s.com>,
Christoph Hellwig <hch@....de>, linux-mips@...ux-mips.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] MIPS: SiByte: Enable swiotlb for SWARM,
LittleSur and BigSur
On Tue, Nov 13, 2018 at 10:42:44PM +0000, Maciej W. Rozycki wrote:
> The Broadcom SiByte BCM1250, BCM1125, and BCM1125H SOCs have an onchip
> DRAM controller that supports memory amounts of up to 16GiB, and due to
> how the address decoder has been wired in the SOC any memory beyond 1GiB
> is actually mapped starting from 4GiB physical up, that is beyond the
> 32-bit addressable limit[1]. Consequently if the maximum amount of
> memory has been installed, then it will span up to 19GiB.
>
> Many of the evaluation boards we support that are based on one of these
> SOCs have their memory soldered and the amount present fits in the
> 32-bit address range. The BCM91250A SWARM board however has actual DIMM
> slots and accepts, depending on the peripherals revision of the SOC, up
> to 4GiB or 8GiB of memory in commercially available JEDEC modules[2].
> I believe this is also the case with the BCM91250C2 LittleSur board.
> This means that up to either 3GiB or 7GiB of memory requires 64-bit
> addressing to access.
>
> I believe the BCM91480B BigSur board, which has the BCM1480 SOC instead,
> accepts at least as much memory, although I have no documentation or
> actual hardware available to verify that.
>
> Both systems have PCI slots installed for use by any PCI option boards,
> including ones that only support 32-bit addressing (additionally the
> 32-bit PCI host bridge of the BCM1250, BCM1125, and BCM1125H SOCs limits
> addressing to 32-bits), and there is no IOMMU available. Therefore for
> PCI DMA to work in the presence of memory beyond enable swiotlb for the
> affected systems.
>
> All the other SOC onchip DMA devices use 40-bit addressing and therefore
> can address the whole memory, so only enable swiotlb if PCI support and
> support for DMA beyond 4GiB have been both enabled in the configuration
> of the kernel.
>
> This shows up as follows:
>
> Broadcom SiByte BCM1250 B2 @ 800 MHz (SB1 rev 2)
> Board type: SiByte BCM91250A (SWARM)
> Determined physical RAM map:
> memory: 000000000fe7fe00 @ 0000000000000000 (usable)
> memory: 000000001ffffe00 @ 0000000080000000 (usable)
> memory: 000000000ffffe00 @ 00000000c0000000 (usable)
> memory: 0000000087fffe00 @ 0000000100000000 (usable)
> software IO TLB: mapped [mem 0xcbffc000-0xcfffc000] (64MB)
>
> in the bootstrap log and removes failures like these:
>
> defxx 0000:02:00.0: dma_direct_map_page: overflow 0x0000000185bc6080+4608 of device mask ffffffff bus mask 0
> fddi0: Receive buffer allocation failed
> fddi0: Adapter open failed!
> IP-Config: Failed to open fddi0
> defxx 0000:09:08.0: dma_direct_map_page: overflow 0x0000000185bc6080+4608 of device mask ffffffff bus mask 0
> fddi1: Receive buffer allocation failed
> fddi1: Adapter open failed!
> IP-Config: Failed to open fddi1
>
> when memory beyond 4GiB is handed out to devices that can only do 32-bit
> addressing.
>
> This updates commit cce335ae47e2 ("[MIPS] 64-bit Sibyte kernels need
> DMA32.").
>
> References:
>
> [1] "BCM1250/BCM1125/BCM1125H User Manual", Revision 1250_1125-UM100-R,
> Broadcom Corporation, 21 Oct 2002, Section 3: "System Overview",
> "Memory Map", pp. 34-38
>
> [2] "BCM91250A User Manual", Revision 91250A-UM100-R, Broadcom
> Corporation, 18 May 2004, Section 3: "Physical Description",
> "Supported DRAM", p. 23
>
> Signed-off-by: Maciej W. Rozycki <macro@...ux-mips.org>
> References: cce335ae47e2 ("[MIPS] 64-bit Sibyte kernels need DMA32.")
> ---
> Changes from v2:
>
> - missing reference to [1] added.
>
> Changes from v1:
>
> - title updated to include LittleSur.
> ---
> arch/mips/Kconfig | 3 +++
> arch/mips/sibyte/common/Makefile | 1 +
> arch/mips/sibyte/common/dma.c | 19 +++++++++++++++++++
> 3 files changed, 23 insertions(+)
>
> linux-mips-sibyte-swiotlb.diff
> Index: linux-20181104-swarm64-eb/arch/mips/Kconfig
> ===================================================================
> --- linux-20181104-swarm64-eb.orig/arch/mips/Kconfig
> +++ linux-20181104-swarm64-eb/arch/mips/Kconfig
> @@ -794,6 +794,7 @@ config SIBYTE_SWARM
> select SYS_SUPPORTS_HIGHMEM
> select SYS_SUPPORTS_LITTLE_ENDIAN
> select ZONE_DMA32 if 64BIT
> + select SWIOTLB if ARCH_DMA_ADDR_T_64BIT && PCI
>
> config SIBYTE_LITTLESUR
> bool "Sibyte BCM91250C2-LittleSur"
> @@ -805,6 +806,7 @@ config SIBYTE_LITTLESUR
> select SYS_SUPPORTS_BIG_ENDIAN
> select SYS_SUPPORTS_HIGHMEM
> select SYS_SUPPORTS_LITTLE_ENDIAN
> + select SWIOTLB if ARCH_DMA_ADDR_T_64BIT && PCI
>
> config SIBYTE_SENTOSA
> bool "Sibyte BCM91250E-Sentosa"
> @@ -826,6 +828,7 @@ config SIBYTE_BIGSUR
> select SYS_SUPPORTS_HIGHMEM
> select SYS_SUPPORTS_LITTLE_ENDIAN
> select ZONE_DMA32 if 64BIT
> + select SWIOTLB if ARCH_DMA_ADDR_T_64BIT && PCI
>
> config SNI_RM
> bool "SNI RM200/300/400"
> Index: linux-20181104-swarm64-eb/arch/mips/sibyte/common/Makefile
> ===================================================================
> --- linux-20181104-swarm64-eb.orig/arch/mips/sibyte/common/Makefile
> +++ linux-20181104-swarm64-eb/arch/mips/sibyte/common/Makefile
> @@ -1,4 +1,5 @@
> obj-y := cfe.o
> +obj-$(CONFIG_SWIOTLB) += dma.o
> obj-$(CONFIG_SIBYTE_BUS_WATCHER) += bus_watcher.o
> obj-$(CONFIG_SIBYTE_CFE_CONSOLE) += cfe_console.o
> obj-$(CONFIG_SIBYTE_TBPROF) += sb_tbprof.o
> Index: linux-20181104-swarm64-eb/arch/mips/sibyte/common/dma.c
> ===================================================================
> --- /dev/null
> +++ linux-20181104-swarm64-eb/arch/mips/sibyte/common/dma.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * DMA support for Broadcom SiByte platforms.
> + *
> + * Copyright (c) 2018 Maciej W. Rozycki
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
Ok, so you have the SPDX tag, but also the duplicate license text,
which is what confused me earlier.
This should just be:
// SPDX-License-Identifier: GPL-2.0+
/*
* DMA support for Broadcom SiByte platforms.
*
* Copyright (c) 2018 Maciej W. Rozycki
*/
With that looks good to me:
Reviewed-by: Christoph Hellwig <hch@....de>
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