4.18-stable review patch. If anyone has any objections, please let me know.
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From: Maciej W. Rozycki macro@linux-mips.org
commit 3f2aa244ee1a0d17ed5b6c86564d2c1b24d1c96b upstream.
Fix a TURBOchannel support regression with commit 205e1b7f51e4 ("dma-mapping: warn when there is no coherent_dma_mask") that caused coherent DMA allocations to produce a warning such as:
defxx: v1.11 2014/07/01 Lawrence V. Stefani and others tc1: DEFTA at MMIO addr = 0x1e900000, IRQ = 20, Hardware addr = 08-00-2b-a3-a3-29 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1 at ./include/linux/dma-mapping.h:516 dfx_dev_register+0x670/0x678 Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 4.19.0-rc6 #2 Stack : ffffffff8009ffc0 fffffffffffffec0 0000000000000000 ffffffff80647650 0000000000000000 0000000000000000 ffffffff806f5f80 ffffffffffffffff 0000000000000000 0000000000000000 0000000000000001 ffffffff8065d4e8 98000000031b6300 ffffffff80563478 ffffffff805685b0 ffffffffffffffff 0000000000000000 ffffffff805d6720 0000000000000204 ffffffff80388df8 0000000000000000 0000000000000009 ffffffff8053efd0 ffffffff806657d0 0000000000000000 ffffffff803177f8 0000000000000000 ffffffff806d0000 9800000003078000 980000000307b9e0 000000001e900000 ffffffff80067940 0000000000000000 ffffffff805d6720 0000000000000204 ffffffff80388df8 ffffffff805176c0 ffffffff8004dc78 0000000000000000 ffffffff80067940 ... Call Trace: [<ffffffff8004dc78>] show_stack+0xa0/0x130 [<ffffffff80067940>] __warn+0x128/0x170 ---[ end trace b1d1e094f67f3bb2 ]---
This is because the TURBOchannel bus driver fails to set the coherent DMA mask for devices enumerated.
Set the regular and coherent DMA masks for TURBOchannel devices then, observing that the bus protocol supports a 34-bit (16GiB) DMA address space, by interpreting the value presented in the address cycle across the 32 `ad' lines as a 32-bit word rather than byte address[1]. The architectural size of the TURBOchannel DMA address space exceeds the maximum amount of RAM any actual TURBOchannel system in existence may have, hence both masks are the same.
This removes the warning shown above.
References:
[1] "TURBOchannel Hardware Specification", EK-369AA-OD-007B, Digital Equipment Corporation, January 1993, Section "DMA", pp. 1-15 -- 1-17
Signed-off-by: Maciej W. Rozycki macro@linux-mips.org Signed-off-by: Paul Burton paul.burton@mips.com Patchwork: https://patchwork.linux-mips.org/patch/20835/ Fixes: 205e1b7f51e4 ("dma-mapping: warn when there is no coherent_dma_mask") Cc: stable@vger.kernel.org # 4.16+ Cc: Ralf Baechle ralf@linux-mips.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tc/tc.c | 8 +++++++- include/linux/tc.h | 1 + 2 files changed, 8 insertions(+), 1 deletion(-)
--- a/drivers/tc/tc.c +++ b/drivers/tc/tc.c @@ -2,7 +2,7 @@ * TURBOchannel bus services. * * Copyright (c) Harald Koerfgen, 1998 - * Copyright (c) 2001, 2003, 2005, 2006 Maciej W. Rozycki + * Copyright (c) 2001, 2003, 2005, 2006, 2018 Maciej W. Rozycki * Copyright (c) 2005 James Simmons * * This file is subject to the terms and conditions of the GNU @@ -10,6 +10,7 @@ * directory of this archive for more details. */ #include <linux/compiler.h> +#include <linux/dma-mapping.h> #include <linux/errno.h> #include <linux/init.h> #include <linux/ioport.h> @@ -92,6 +93,11 @@ static void __init tc_bus_add_devices(st tdev->dev.bus = &tc_bus_type; tdev->slot = slot;
+ /* TURBOchannel has 34-bit DMA addressing (16GiB space). */ + tdev->dma_mask = DMA_BIT_MASK(34); + tdev->dev.dma_mask = &tdev->dma_mask; + tdev->dev.coherent_dma_mask = DMA_BIT_MASK(34); + for (i = 0; i < 8; i++) { tdev->firmware[i] = readb(module + offset + TC_FIRM_VER + 4 * i); --- a/include/linux/tc.h +++ b/include/linux/tc.h @@ -84,6 +84,7 @@ struct tc_dev { device. */ struct device dev; /* Generic device interface. */ struct resource resource; /* Address space of this device. */ + u64 dma_mask; /* DMA addressable range. */ char vendor[9]; char name[9]; char firmware[9];