| Message ID | 20190226202327.5349-1-nicoleotsuka@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Revert "dma-contiguous: do not allocate a single page from CMA area" | expand |
On 2019-02-26 8:23 pm, Nicolin Chen wrote: > This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. > > The original change breaks omap dss: > omapdss_dispc 58001000.dispc: > dispc_errata_i734_wa_init: dma_alloc_writecombine failed > > Let's revert it first and then find a safer solution instead. Ah, I think I see the problem - once arch/arm's __dma_alloc() has decided to use CMA (because dev_get_cma_area(dev) returns the global area), it then won't fall back to trying a regular page allocation if dma_alloc_from_contiguous() returns NULL. Thus anything on 32-bit Arm trying to allocate a single-page buffer in blockable context with a CMA-enabled config is just going to fail. Similarly, it looks like none of the DMA_ATTR_FORCE_CONTIGUOUS cases are prepared to handle this change either (amd_iommu appears technically affected, but is already using dma_alloc_from_contiguous() backwards compared to everyone else, hmm). I guess the question is whether to add alloc_page()/free_page() fallbacks to those call sites, or stuff them directly into the CMA helpers here. Robin. > Reported-by: Tony Lindgren <tony@atomide.com> > Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> > --- > Tony, > > Would you please test and verify? Thanks! > > kernel/dma/contiguous.c | 22 +++------------------- > 1 file changed, 3 insertions(+), 19 deletions(-) > > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c > index 09074bd04793..b2a87905846d 100644 > --- a/kernel/dma/contiguous.c > +++ b/kernel/dma/contiguous.c > @@ -186,32 +186,16 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, > * > * This function allocates memory buffer for specified device. It uses > * device specific contiguous memory area if available or the default > - * global one. > - * > - * However, it skips one-page size of allocations from the global area. > - * As the addresses within one page are always contiguous, so there is > - * no need to waste CMA pages for that kind; it also helps reduce the > - * fragmentations in the CMA area. So a caller should be the rebounder > - * in such case to allocate a normal page upon NULL return value. > - * > - * Requires architecture specific dev_get_cma_area() helper function. > + * global one. Requires architecture specific dev_get_cma_area() helper > + * function. > */ > struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, > unsigned int align, bool no_warn) > { > - struct cma *cma; > - > if (align > CONFIG_CMA_ALIGNMENT) > align = CONFIG_CMA_ALIGNMENT; > > - if (dev && dev->cma_area) > - cma = dev->cma_area; > - else if (count > 1) > - cma = dma_contiguous_default_area; > - else > - return NULL; > - > - return cma_alloc(cma, count, align, no_warn); > + return cma_alloc(dev_get_cma_area(dev), count, align, no_warn); > } > > /** >
* Robin Murphy <robin.murphy@arm.com> [190226 23:36]: > On 2019-02-26 8:23 pm, Nicolin Chen wrote: > > This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. > > > > The original change breaks omap dss: > > omapdss_dispc 58001000.dispc: > > dispc_errata_i734_wa_init: dma_alloc_writecombine failed > > > > Let's revert it first and then find a safer solution instead. Sounds like a good idea since we're only have few days left before the merge window. > Ah, I think I see the problem - once arch/arm's __dma_alloc() has decided to > use CMA (because dev_get_cma_area(dev) returns the global area), it then > won't fall back to trying a regular page allocation if > dma_alloc_from_contiguous() returns NULL. Thus anything on 32-bit Arm trying > to allocate a single-page buffer in blockable context with a CMA-enabled > config is just going to fail. Similarly, it looks like none of the > DMA_ATTR_FORCE_CONTIGUOUS cases are prepared to handle this change either > (amd_iommu appears technically affected, but is already using > dma_alloc_from_contiguous() backwards compared to everyone else, hmm). > > I guess the question is whether to add alloc_page()/free_page() fallbacks to > those call sites, or stuff them directly into the CMA helpers here. Well if you come up with some test patch, I can easily test it :) > > Would you please test and verify? Thanks! Yes this revert works for me: Tested-by: Tony Lindgren <tony@atomide.com>
On Tue, Feb 26, 2019 at 11:35:44PM +0000, Robin Murphy wrote: > On 2019-02-26 8:23 pm, Nicolin Chen wrote: > > This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. > > > > The original change breaks omap dss: > > omapdss_dispc 58001000.dispc: > > dispc_errata_i734_wa_init: dma_alloc_writecombine failed > > > > Let's revert it first and then find a safer solution instead. > > Ah, I think I see the problem - once arch/arm's __dma_alloc() has decided to > use CMA (because dev_get_cma_area(dev) returns the global area), it then > won't fall back to trying a regular page allocation if > dma_alloc_from_contiguous() returns NULL. Thus anything on 32-bit Arm trying > to allocate a single-page buffer in blockable context with a CMA-enabled > config is just going to fail. Similarly, it looks like none of the > DMA_ATTR_FORCE_CONTIGUOUS cases are prepared to handle this change either > (amd_iommu appears technically affected, but is already using > dma_alloc_from_contiguous() backwards compared to everyone else, hmm). Yea, I searched the tree and got the same results. > I guess the question is whether to add alloc_page()/free_page() fallbacks to > those call sites, or stuff them directly into the CMA helpers here. Probably would be safer/easier to do the later one I feel.
On Tue, 26 Feb 2019 at 21:25, Nicolin Chen <nicoleotsuka@gmail.com> wrote: > > This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. > > The original change breaks omap dss: > omapdss_dispc 58001000.dispc: > dispc_errata_i734_wa_init: dma_alloc_writecombine failed > > Let's revert it first and then find a safer solution instead. > > Reported-by: Tony Lindgren <tony@atomide.com> > Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> > --- > Tony, > > Would you please test and verify? Thanks! > > kernel/dma/contiguous.c | 22 +++------------------- > 1 file changed, 3 insertions(+), 19 deletions(-) This fixes broken (since yesterday) linux-next on Exynos boards (ARMv7), errors like: dma-pl330: probe of 121a0000.pdma failed with error -12 exynos-ehci 12110000.usb: can't setup: -12 exynos-ehci 12110000.usb: USB bus 1 deregistered exynos-ehci 12110000.usb: Failed to add USB HCD Tested-by: Krzysztof Kozlowski <krzk@kernel.org> Best regards, Krzysztof
On 26/02/2019 20:23, Nicolin Chen wrote: > This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. > > The original change breaks omap dss: > omapdss_dispc 58001000.dispc: > dispc_errata_i734_wa_init: dma_alloc_writecombine failed > > Let's revert it first and then find a safer solution instead. > > Reported-by: Tony Lindgren <tony@atomide.com> > Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> > --- > Tony, > > Would you please test and verify? Thanks! This also fixes various memory allocation failures we have seen on 32-bit Tegra as well. Tested-by: Jon Hunter <jonathanh@nvidia.com> Cheers Jon
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 09074bd04793..b2a87905846d 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -186,32 +186,16 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, * * This function allocates memory buffer for specified device. It uses * device specific contiguous memory area if available or the default - * global one. - * - * However, it skips one-page size of allocations from the global area. - * As the addresses within one page are always contiguous, so there is - * no need to waste CMA pages for that kind; it also helps reduce the - * fragmentations in the CMA area. So a caller should be the rebounder - * in such case to allocate a normal page upon NULL return value. - * - * Requires architecture specific dev_get_cma_area() helper function. + * global one. Requires architecture specific dev_get_cma_area() helper + * function. */ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, unsigned int align, bool no_warn) { - struct cma *cma; - if (align > CONFIG_CMA_ALIGNMENT) align = CONFIG_CMA_ALIGNMENT; - if (dev && dev->cma_area) - cma = dev->cma_area; - else if (count > 1) - cma = dma_contiguous_default_area; - else - return NULL; - - return cma_alloc(cma, count, align, no_warn); + return cma_alloc(dev_get_cma_area(dev), count, align, no_warn); } /**
This reverts commit d222e42e88168fd67e6d131984b86477af1fc256. The original change breaks omap dss: omapdss_dispc 58001000.dispc: dispc_errata_i734_wa_init: dma_alloc_writecombine failed Let's revert it first and then find a safer solution instead. Reported-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> --- Tony, Would you please test and verify? Thanks! kernel/dma/contiguous.c | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-)