Re: [PATCH 5.10 81/97] MIPS: Loongson64: Enable DMA noncoherent support

[Salvatore Bonaccorso <carnil@debian.org>]

Hi,

On Sat, Dec 30, 2023 at 11:16:41PM +0000, Jiaxun Yang wrote:
> 
> 
> 在2023年12月30日十二月 下午7:38，Salvatore Bonaccorso写道：
> > Hi,
> >
> > On Mon, Dec 11, 2023 at 07:22:24PM +0100, Greg Kroah-Hartman wrote:
> >> 5.10-stable review patch.  If anyone has any objections, please let me know.
> >> 
> >> ------------------
> >> 
> >> From: Jiaxun Yang <jiaxun.yang@flygoat.com>
> >> 
> >> commit edc0378eee00200a5bedf1bb9f00ad390e0d1bd4 upstream.
> >> 
> >> There are some Loongson64 systems come with broken coherent DMA
> >> support, firmware will set a bit in boot_param and pass nocoherentio
> >> in cmdline.
> >> 
> >> However nonconherent support was missed out when spin off Loongson-2EF
> >> form Loongson64, and that boot_param change never made itself into
> >> upstream.
> >> 
> >> Support DMA noncoherent properly to get those systems working.
> >> 
> >> Cc: stable@vger.kernel.org
> >> Fixes: 71e2f4dd5a65 ("MIPS: Fork loongson2ef from loongson64")
> >> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> >> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> >> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >> ---
> >>  arch/mips/Kconfig                                  |    2 ++
> >>  arch/mips/include/asm/mach-loongson64/boot_param.h |    3 ++-
> >>  arch/mips/loongson64/env.c                         |   10 +++++++++-
> >>  3 files changed, 13 insertions(+), 2 deletions(-)
> >> 
> >> --- a/arch/mips/Kconfig
> >> +++ b/arch/mips/Kconfig
> >> @@ -468,6 +468,7 @@ config MACH_LOONGSON2EF
> >>  
> >>  config MACH_LOONGSON64
> >>  	bool "Loongson 64-bit family of machines"
> >> +	select ARCH_DMA_DEFAULT_COHERENT
> >>  	select ARCH_SPARSEMEM_ENABLE
> >>  	select ARCH_MIGHT_HAVE_PC_PARPORT
> >>  	select ARCH_MIGHT_HAVE_PC_SERIO
> >> @@ -1379,6 +1380,7 @@ config CPU_LOONGSON64
> >>  	select CPU_SUPPORTS_MSA
> >>  	select CPU_DIEI_BROKEN if !LOONGSON3_ENHANCEMENT
> >>  	select CPU_MIPSR2_IRQ_VI
> >> +	select DMA_NONCOHERENT
> >>  	select WEAK_ORDERING
> >>  	select WEAK_REORDERING_BEYOND_LLSC
> >>  	select MIPS_ASID_BITS_VARIABLE
> >> --- a/arch/mips/include/asm/mach-loongson64/boot_param.h
> >> +++ b/arch/mips/include/asm/mach-loongson64/boot_param.h
> >> @@ -117,7 +117,8 @@ struct irq_source_routing_table {
> >>  	u64 pci_io_start_addr;
> >>  	u64 pci_io_end_addr;
> >>  	u64 pci_config_addr;
> >> -	u32 dma_mask_bits;
> >> +	u16 dma_mask_bits;
> >> +	u16 dma_noncoherent;
> >>  } __packed;
> >>  
> >>  struct interface_info {
> >> --- a/arch/mips/loongson64/env.c
> >> +++ b/arch/mips/loongson64/env.c
> >> @@ -13,6 +13,8 @@
> >>   * Copyright (C) 2009 Lemote Inc.
> >>   * Author: Wu Zhangjin, wuzhangjin@gmail.com
> >>   */
> >> +
> >> +#include <linux/dma-map-ops.h>
> >>  #include <linux/export.h>
> >>  #include <linux/pci_ids.h>
> >>  #include <asm/bootinfo.h>
> >> @@ -131,8 +133,14 @@ void __init prom_init_env(void)
> >>  	loongson_sysconf.pci_io_base = eirq_source->pci_io_start_addr;
> >>  	loongson_sysconf.dma_mask_bits = eirq_source->dma_mask_bits;
> >>  	if (loongson_sysconf.dma_mask_bits < 32 ||
> >> -		loongson_sysconf.dma_mask_bits > 64)
> >> +			loongson_sysconf.dma_mask_bits > 64) {
> >>  		loongson_sysconf.dma_mask_bits = 32;
> >> +		dma_default_coherent = true;
> >> +	} else {
> >> +		dma_default_coherent = !eirq_source->dma_noncoherent;
> >> +	}
> >> +
> >> +	pr_info("Firmware: Coherent DMA: %s\n", dma_default_coherent ? "on" : "off");
> >>  
> >>  	loongson_sysconf.restart_addr = boot_p->reset_system.ResetWarm;
> >>  	loongson_sysconf.poweroff_addr = boot_p->reset_system.Shutdown;
> >
> > While preparing an update for Debian and finally building for all
> > supported architecture, the builds for mipsel and mips64el were
> > failing with:
> >
> > /<<PKGBUILDDIR>>/arch/mips/loongson64/env.c: In function 
> > 'prom_init_env':
> > /<<PKGBUILDDIR>>/arch/mips/loongson64/env.c:138:3: error: 
> > 'dma_default_coherent' undeclared (first use in this function); did you 
> > mean 'dma_free_coherent'?
> >   138 |   dma_default_coherent = true;
> >       |   ^~~~~~~~~~~~~~~~~~~~
> >       |   dma_free_coherent
> > /<<PKGBUILDDIR>>/arch/mips/loongson64/env.c:138:3: note: each 
> > undeclared identifier is reported only once for each function it 
> > appears in
> > make[6]: *** [/<<PKGBUILDDIR>>/scripts/Makefile.build:291: 
> > arch/mips/loongson64/env.o] Error 1
> > make[6]: *** Waiting for unfinished jobs....
> >
> > Is here a prerequisite missing for the commit?
> >
> > Backporting though 6d4e9a8efe3d ("driver core: lift dma_default_coherent into
> > common code") which is from 5.12-rc1 though seems too intrusive, correct? Would
> > the alternative be to just revert the 3ee7e2faef87 ("MIPS: Loongson64: Enable
> > DMA noncoherent support") commit which landed in 5.10.204?
> 
> Hi,
> 
> Sorry for not spotting the issue in the first place.
> 
> It actually requires more dependencies such as c00a60d6f4a1 ("of: address: always
> use dma_default_coherent for default coherency").
> 
> I'll try to produce a backport series but better to drop this patch from stable
> for now.

Thanks a lot for your quick reply! 

So I guess it only needs a revert for now from 5.10.y correct?

Greg, possible to already queue up the revert for 5.10.y for the next
upload?

Regards,
Salvatore