| Message ID | 20230222133712.8079-3-jiaxun.yang@flygoat.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | Use dma_default_coherent for devicetree default coherency | expand |
On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote: > For riscv our assumption is unless a device states it is non-coherent, > we take it to be DMA coherent. > > For devicetree probed devices that have been true since very begining > with OF_DMA_DEFAULT_COHERENT selected. > > Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> > --- > arch/riscv/kernel/setup.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 376d2827e736..34b371180976 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) > riscv_init_cbom_blocksize(); > riscv_fill_hwcap(); > apply_boot_alternatives(); > +#ifdef CONFIG_RISCV_DMA_NONCOHERENT > + dma_default_coherent = true; > +#endif Do we really need to add ifdeffery for this here? It's always coherent by default, so why do we need to say set it in setup_arch() when we know that, regardless of options, it is true? Cheers, Conor. > if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) && > riscv_isa_extension_available(NULL, ZICBOM)) > riscv_noncoherent_supported(); > -- > 2.37.1 (Apple Git-137.1) >
> 2023年2月22日 14:50，Conor Dooley <conor@kernel.org> 写道： > > On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote: >> For riscv our assumption is unless a device states it is non-coherent, >> we take it to be DMA coherent. >> >> For devicetree probed devices that have been true since very begining >> with OF_DMA_DEFAULT_COHERENT selected. >> >> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> >> --- >> arch/riscv/kernel/setup.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c >> index 376d2827e736..34b371180976 100644 >> --- a/arch/riscv/kernel/setup.c >> +++ b/arch/riscv/kernel/setup.c >> @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) >> riscv_init_cbom_blocksize(); >> riscv_fill_hwcap(); >> apply_boot_alternatives(); >> +#ifdef CONFIG_RISCV_DMA_NONCOHERENT >> + dma_default_coherent = true; >> +#endif > > Do we really need to add ifdeffery for this here? > It's always coherent by default, so why do we need to say set it in > setup_arch() when we know that, regardless of options, it is true? Because this symbol is only a variable when: defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) Which is only true if CONFIG_RISCV_DMA_NONCOHERENT is selected. Otherwise this symbol is defined to true and we can’t make a assignment to it. Thanks - Jiaxun > > Cheers, > Conor. > >> if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) && >> riscv_isa_extension_available(NULL, ZICBOM)) >> riscv_noncoherent_supported(); >> -- >> 2.37.1 (Apple Git-137.1)
On Wed, Feb 22, 2023 at 03:55:19PM +0000, Jiaxun Yang wrote: > > > > 2023年2月22日 14:50，Conor Dooley <conor@kernel.org> 写道： > > > > On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote: > >> For riscv our assumption is unless a device states it is non-coherent, > >> we take it to be DMA coherent. > >> > >> For devicetree probed devices that have been true since very begining > >> with OF_DMA_DEFAULT_COHERENT selected. > >> > >> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> > >> --- > >> arch/riscv/kernel/setup.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > >> index 376d2827e736..34b371180976 100644 > >> --- a/arch/riscv/kernel/setup.c > >> +++ b/arch/riscv/kernel/setup.c > >> @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) > >> riscv_init_cbom_blocksize(); > >> riscv_fill_hwcap(); > >> apply_boot_alternatives(); > >> +#ifdef CONFIG_RISCV_DMA_NONCOHERENT > >> + dma_default_coherent = true; > >> +#endif > > > > Do we really need to add ifdeffery for this here? > > It's always coherent by default, so why do we need to say set it in > > setup_arch() when we know that, regardless of options, it is true? > > Because this symbol is only a variable when: > > defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ > defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ > defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) > > Which is only true if CONFIG_RISCV_DMA_NONCOHERENT is selected. > > Otherwise this symbol is defined to true and we can’t make a assignment to it. Maybe I am just slow today, but I don't get why you need to add ifdeffery to setup_arch() to do something that is always true. Why can't you just set this in riscv/mm/dma-noncoherent.c? What am I missing? Cheers, Conor. > >> if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) && > >> riscv_isa_extension_available(NULL, ZICBOM)) > >> riscv_noncoherent_supported(); > >> -- > >> 2.37.1 (Apple Git-137.1) > >
> 2023年2月22日 16:02，Conor Dooley <conor@kernel.org> 写道： > > On Wed, Feb 22, 2023 at 03:55:19PM +0000, Jiaxun Yang wrote: >> >> >>> 2023年2月22日 14:50，Conor Dooley <conor@kernel.org> 写道： >>> >>> On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote: >>>> For riscv our assumption is unless a device states it is non-coherent, >>>> we take it to be DMA coherent. >>>> >>>> For devicetree probed devices that have been true since very begining >>>> with OF_DMA_DEFAULT_COHERENT selected. >>>> >>>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> >>>> --- >>>> arch/riscv/kernel/setup.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>> >>>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c >>>> index 376d2827e736..34b371180976 100644 >>>> --- a/arch/riscv/kernel/setup.c >>>> +++ b/arch/riscv/kernel/setup.c >>>> @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) >>>> riscv_init_cbom_blocksize(); >>>> riscv_fill_hwcap(); >>>> apply_boot_alternatives(); >>>> +#ifdef CONFIG_RISCV_DMA_NONCOHERENT >>>> + dma_default_coherent = true; >>>> +#endif >>> >>> Do we really need to add ifdeffery for this here? >>> It's always coherent by default, so why do we need to say set it in >>> setup_arch() when we know that, regardless of options, it is true? >> >> Because this symbol is only a variable when: >> >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) >> >> Which is only true if CONFIG_RISCV_DMA_NONCOHERENT is selected. >> >> Otherwise this symbol is defined to true and we can’t make a assignment to it. > > Maybe I am just slow today, but I don't get why you need to add > ifdeffery to setup_arch() to do something that is always true. > Why can't you just set this in riscv/mm/dma-noncoherent.c? What am I > missing? Hmm that sounds like a good idea but I was unable to find a place for this. riscv/mm/dma-noncoherent.c are just a bunch of callbacks, there is no initialisation function that will always run on every boot. riscv_noncoherent_supported is only called conditionally. Perhaps I can add a initcall in dma-noncoherent.c but it seems to be a little bit overkilling. Actually I’d prefer to have a config option for the default value but it seems like it’s not in Christoph’s flavour. Thanks - Jiaxun
On Wed, Feb 22, 2023 at 04:20:16PM +0000, Jiaxun Yang wrote: > > 2023年2月22日 16:02，Conor Dooley <conor@kernel.org> 写道： > > On Wed, Feb 22, 2023 at 03:55:19PM +0000, Jiaxun Yang wrote: > >>> 2023年2月22日 14:50，Conor Dooley <conor@kernel.org> 写道： > >>> On Wed, Feb 22, 2023 at 01:37:11PM +0000, Jiaxun Yang wrote: > >>>> For riscv our assumption is unless a device states it is non-coherent, > >>>> we take it to be DMA coherent. > >>>> > >>>> For devicetree probed devices that have been true since very begining > >>>> with OF_DMA_DEFAULT_COHERENT selected. > >>>> > >>>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> > >>>> --- > >>>> arch/riscv/kernel/setup.c | 3 +++ > >>>> 1 file changed, 3 insertions(+) > >>>> > >>>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > >>>> index 376d2827e736..34b371180976 100644 > >>>> --- a/arch/riscv/kernel/setup.c > >>>> +++ b/arch/riscv/kernel/setup.c > >>>> @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) > >>>> riscv_init_cbom_blocksize(); > >>>> riscv_fill_hwcap(); > >>>> apply_boot_alternatives(); > >>>> +#ifdef CONFIG_RISCV_DMA_NONCOHERENT > >>>> + dma_default_coherent = true; > >>>> +#endif > >>> > >>> Do we really need to add ifdeffery for this here? > >>> It's always coherent by default, so why do we need to say set it in > >>> setup_arch() when we know that, regardless of options, it is true? > >> > >> Because this symbol is only a variable when: > >> > >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ > >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ > >> defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) > >> > >> Which is only true if CONFIG_RISCV_DMA_NONCOHERENT is selected. > >> > >> Otherwise this symbol is defined to true and we can’t make a assignment to it. > > Maybe I am just slow today, but I don't get why you need to add > > ifdeffery to setup_arch() to do something that is always true. > > Why can't you just set this in riscv/mm/dma-noncoherent.c? What am I > > missing? > > Hmm that sounds like a good idea but I was unable to find a place for this. > > riscv/mm/dma-noncoherent.c are just a bunch of callbacks, there is no initialisation > function that will always run on every boot. riscv_noncoherent_supported is only > called conditionally. Right, that's fair. riscv_noncoherent_supported() is for when we know we can support non-coherent DMA, not to detect whether we can, hence the conditional nature. Apologies for sending you on a wild goose chase there. > Perhaps I can add a initcall in dma-noncoherent.c but it seems to be a little bit > overkilling. Yah, probably would be. > Actually I’d prefer to have a config option for the default value but it seems like > it’s not in Christoph’s flavour. We already have a config option that sets things up nicely for RISC-V that you're getting rid of! ;)
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 376d2827e736..34b371180976 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -300,6 +300,9 @@ void __init setup_arch(char **cmdline_p) riscv_init_cbom_blocksize(); riscv_fill_hwcap(); apply_boot_alternatives(); +#ifdef CONFIG_RISCV_DMA_NONCOHERENT + dma_default_coherent = true; +#endif if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) && riscv_isa_extension_available(NULL, ZICBOM)) riscv_noncoherent_supported();
For riscv our assumption is unless a device states it is non-coherent, we take it to be DMA coherent. For devicetree probed devices that have been true since very begining with OF_DMA_DEFAULT_COHERENT selected. Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com> --- arch/riscv/kernel/setup.c | 3 +++ 1 file changed, 3 insertions(+)