| Message ID | 20200714121856.955680-10-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/10] sh: remove -Werror from Makefiles | expand |
On Tue, Jul 14, 2020 at 02:18:55PM +0200, Christoph Hellwig wrote: > The code handling non-coherent DMA depends on being able to remap code > as non-cached. But that can't be done without an MMU, so using this > option on NOMMU builds is broken. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > arch/sh/Kconfig | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig > index f8027eee08edae..337eb496c45a0a 100644 > --- a/arch/sh/Kconfig > +++ b/arch/sh/Kconfig > @@ -61,6 +61,7 @@ config SUPERH > select MAY_HAVE_SPARSE_IRQ > select MODULES_USE_ELF_RELA > select NEED_SG_DMA_LENGTH > + select NO_DMA if !MMU && !DMA_COHERENT > select NO_GENERIC_PCI_IOPORT_MAP if PCI > select OLD_SIGACTION > select OLD_SIGSUSPEND > @@ -135,7 +136,7 @@ config DMA_COHERENT > bool This change broke SD card support on J2 because MMC_SPI spuriously depends on HAS_DMA. It looks like it can be fixed just by removing that dependency from drivers/mmc/host/Kconfig. Rich
On Thu, Aug 27, 2020 at 10:00:48PM -0400, Rich Felker wrote: > On Tue, Jul 14, 2020 at 02:18:55PM +0200, Christoph Hellwig wrote: > > The code handling non-coherent DMA depends on being able to remap code > > as non-cached. But that can't be done without an MMU, so using this > > option on NOMMU builds is broken. > > > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > --- > > arch/sh/Kconfig | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig > > index f8027eee08edae..337eb496c45a0a 100644 > > --- a/arch/sh/Kconfig > > +++ b/arch/sh/Kconfig > > @@ -61,6 +61,7 @@ config SUPERH > > select MAY_HAVE_SPARSE_IRQ > > select MODULES_USE_ELF_RELA > > select NEED_SG_DMA_LENGTH > > + select NO_DMA if !MMU && !DMA_COHERENT > > select NO_GENERIC_PCI_IOPORT_MAP if PCI > > select OLD_SIGACTION > > select OLD_SIGSUSPEND > > @@ -135,7 +136,7 @@ config DMA_COHERENT > > bool > > This change broke SD card support on J2 because MMC_SPI spuriously > depends on HAS_DMA. It looks like it can be fixed just by removing > that dependency from drivers/mmc/host/Kconfig. It can't. mmp_spi_probe fails with ENOMEM, probably due to trying to do some DMA setup thing that's not going to be needed if the underlying SPI device doesn't support/use DMA. Rich
On Thu, Aug 27, 2020 at 10:11:53PM -0400, Rich Felker wrote: > > This change broke SD card support on J2 because MMC_SPI spuriously > > depends on HAS_DMA. It looks like it can be fixed just by removing > > that dependency from drivers/mmc/host/Kconfig. > > It can't. mmp_spi_probe fails with ENOMEM, probably due to trying to > do some DMA setup thing that's not going to be needed if the > underlying SPI device doesn't support/use DMA. Adding the linux-mmc and linux-spi lists, as that seems pretty odd.
On Fri, 28 Aug 2020 at 06:24, Christoph Hellwig <hch@lst.de> wrote: > > On Thu, Aug 27, 2020 at 10:11:53PM -0400, Rich Felker wrote: > > > This change broke SD card support on J2 because MMC_SPI spuriously > > > depends on HAS_DMA. It looks like it can be fixed just by removing > > > that dependency from drivers/mmc/host/Kconfig. > > > > It can't. mmp_spi_probe fails with ENOMEM, probably due to trying to > > do some DMA setup thing that's not going to be needed if the > > underlying SPI device doesn't support/use DMA. > > Adding the linux-mmc and linux-spi lists, as that seems pretty odd. The mmc_spi driver needs modernizations, so I am not surprised to see odd things. My guess is that in ->probe() we check "if (spi->master->dev.parent->dma_mask)" - > and runs dma_map*() operations, which fails and leads to bailing out of ->probe() to return an error code. However, by looking at the code, one get the feeling that the DMA support is somewhat prepared to be made optional. I guess it has never been really tested, as the Kconfig option has "depends on HAS_DMA" - and it's been like that as long as I can remember. Kind regards Uffe
On Fri, Aug 28, 2020 at 11:26:57AM +0200, Ulf Hansson wrote: > On Fri, 28 Aug 2020 at 06:24, Christoph Hellwig <hch@lst.de> wrote: > > > > On Thu, Aug 27, 2020 at 10:11:53PM -0400, Rich Felker wrote: > > > > This change broke SD card support on J2 because MMC_SPI spuriously > > > > depends on HAS_DMA. It looks like it can be fixed just by removing > > > > that dependency from drivers/mmc/host/Kconfig. > > > > > > It can't. mmp_spi_probe fails with ENOMEM, probably due to trying to > > > do some DMA setup thing that's not going to be needed if the > > > underlying SPI device doesn't support/use DMA. > > > > Adding the linux-mmc and linux-spi lists, as that seems pretty odd. > > The mmc_spi driver needs modernizations, so I am not surprised to see > odd things. > > My guess is that in ->probe() we check "if > (spi->master->dev.parent->dma_mask)" - > and runs dma_map*() > operations, which fails and leads to bailing out of ->probe() to > return an error code. > > However, by looking at the code, one get the feeling that the DMA > support is somewhat prepared to be made optional. I guess it has never > been really tested, as the Kconfig option has "depends on HAS_DMA" - > and it's been like that as long as I can remember. It always worked on our "byte-banged" SPI controller, with no DMA controller present, before Christoph's changes in this patch series, and seems to be working now (although I have some other, hopefully unrelated regressions to debug) with #ifdef CONFIG_HAS_DMA around the if (spi->master->dev.parent->dma_mask) block in mmc_spi_probe. That's probably not the right fix though -- why isn't it checking host->dma_dev instead and only attempting DMA setup if dma_dev is non-null? Rich
On Fri, Aug 28, 2020 at 11:09:43AM -0400, Rich Felker wrote: > > However, by looking at the code, one get the feeling that the DMA > > support is somewhat prepared to be made optional. I guess it has never > > been really tested, as the Kconfig option has "depends on HAS_DMA" - > > and it's been like that as long as I can remember. > > It always worked on our "byte-banged" SPI controller, with no DMA > controller present, before Christoph's changes in this patch series, Before that nommu sh builds provided a DMA mapping implementation that even worked for the streaming side (dma_map_*), but would corrupt data if you used dma_alloc_coherent memory to communicate with the device. > and seems to be working now (although I have some other, hopefully > unrelated regressions to debug) with #ifdef CONFIG_HAS_DMA around the > if (spi->master->dev.parent->dma_mask) block in mmc_spi_probe. That's > probably not the right fix though -- why isn't it checking > host->dma_dev instead and only attempting DMA setup if dma_dev is > non-null? I don't think dma_dev can be NULL right now. dma_dev is assigned here: if (spi->master->dev.parent->dma_mask) { struct device *dev = spi->master->dev.parent; host->dma_dev = dev; but for any OF or real bus device dma_mask never is zero (it actually is a pointer), and the value of it also is initialized to 32-bit by default, making this effectively an "if (1) {". The driver needs some way to communicate if a given device actually is DMA capable or not. Or is that purely a factor of the platform which would be a little strange. In which case we should do something like: diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c index 39bb1e30c2d722..3b0cc9a70e6432 100644 --- a/drivers/mmc/host/mmc_spi.c +++ b/drivers/mmc/host/mmc_spi.c @@ -1374,7 +1374,7 @@ static int mmc_spi_probe(struct spi_device *spi) if (!host->data) goto fail_nobuf1; - if (spi->master->dev.parent->dma_mask) { + if (IS_ENABLED(CONFIG_HAS_DMA)) { struct device *dev = spi->master->dev.parent; host->dma_dev = dev;
On Sat, 29 Aug 2020 at 10:31, Christoph Hellwig <hch@lst.de> wrote: > > On Fri, Aug 28, 2020 at 11:09:43AM -0400, Rich Felker wrote: > > > However, by looking at the code, one get the feeling that the DMA > > > support is somewhat prepared to be made optional. I guess it has never > > > been really tested, as the Kconfig option has "depends on HAS_DMA" - > > > and it's been like that as long as I can remember. > > > > It always worked on our "byte-banged" SPI controller, with no DMA > > controller present, before Christoph's changes in this patch series, > > Before that nommu sh builds provided a DMA mapping implementation > that even worked for the streaming side (dma_map_*), but would corrupt > data if you used dma_alloc_coherent memory to communicate with the > device. I see. > > > and seems to be working now (although I have some other, hopefully > > unrelated regressions to debug) with #ifdef CONFIG_HAS_DMA around the > > if (spi->master->dev.parent->dma_mask) block in mmc_spi_probe. That's > > probably not the right fix though -- why isn't it checking > > host->dma_dev instead and only attempting DMA setup if dma_dev is > > non-null? > > I don't think dma_dev can be NULL right now. dma_dev is assigned here: > > if (spi->master->dev.parent->dma_mask) { > struct device *dev = spi->master->dev.parent; > > host->dma_dev = dev; > > but for any OF or real bus device dma_mask never is zero (it actually is > a pointer), and the value of it also is initialized to 32-bit by default, > making this effectively an "if (1) {". The driver needs some way to > communicate if a given device actually is DMA capable or not. Or is that > purely a factor of the platform which would be a little strange. Okay, thanks for clarifying things. > > In which case we should do something like: > > > diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c > index 39bb1e30c2d722..3b0cc9a70e6432 100644 > --- a/drivers/mmc/host/mmc_spi.c > +++ b/drivers/mmc/host/mmc_spi.c > @@ -1374,7 +1374,7 @@ static int mmc_spi_probe(struct spi_device *spi) > if (!host->data) > goto fail_nobuf1; > > - if (spi->master->dev.parent->dma_mask) { > + if (IS_ENABLED(CONFIG_HAS_DMA)) { I guess "#ifdef CONFIG_HAS_DMA", would work as well as CONFIG_HAS_DMA can't be "m". I would also suggest moving the DMA setup things into a separate function. Then when CONFIG_HAS_DMA is unset, we can use a stub. > struct device *dev = spi->master->dev.parent; > > host->dma_dev = dev; Let me cook a patch that we can try. Kind regards Uffe
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index f8027eee08edae..337eb496c45a0a 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -61,6 +61,7 @@ config SUPERH select MAY_HAVE_SPARSE_IRQ select MODULES_USE_ELF_RELA select NEED_SG_DMA_LENGTH + select NO_DMA if !MMU && !DMA_COHERENT select NO_GENERIC_PCI_IOPORT_MAP if PCI select OLD_SIGACTION select OLD_SIGSUSPEND @@ -135,7 +136,7 @@ config DMA_COHERENT bool config DMA_NONCOHERENT - def_bool !DMA_COHERENT + def_bool !NO_DMA && !DMA_COHERENT select ARCH_HAS_SYNC_DMA_FOR_DEVICE config PGTABLE_LEVELS
The code handling non-coherent DMA depends on being able to remap code as non-cached. But that can't be done without an MMU, so using this option on NOMMU builds is broken. Signed-off-by: Christoph Hellwig <hch@lst.de> --- arch/sh/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)