Hi Atish, Am Montag, 20. Juni 2022, 18:33:09 CEST schrieb Atish Patra: > On Sun, Jun 19, 2022 at 1:32 PM Heiko Stuebner <heiko@xxxxxxxxx> wrote: > > > > of_dma_is_coherent() currently expects the architecture to be > > non-coherent and some devices being coherent getting marked > > as such with the dma-coherent devicetree property. > > > > For PowerPC CONFIG_OF_DMA_DEFAULT_COHERENT was added which currently > > makes of_dma_is_coherent() always return true but doesn't handle > > the case of the architecture being coherent but some devices not. > > > > So modify the function to also check for dma-noncoherent and > > set a suitable default return value. If CONFIG_OF_DMA_DEFAULT_COHERENT > > is set the value starts with true and finding dma-noncoherent will > > set it to false and without CONFIG_OF_DMA_DEFAULT_COHERENT, the > > behaviour is reversed. > > > > Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx> > > --- > > drivers/of/address.c | 16 +++++++++++----- > > 1 file changed, 11 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/of/address.c b/drivers/of/address.c > > index 94f017d808c4..1c362d09983d 100644 > > --- a/drivers/of/address.c > > +++ b/drivers/of/address.c > > @@ -1045,26 +1045,32 @@ phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np) > > * > > * It returns true if "dma-coherent" property was found > > * for this device in the DT, or if DMA is coherent by > > - * default for OF devices on the current platform. > > + * default for OF devices on the current platform and no > > + * "dma-noncoherent" property was found for this device. > > "dma-noncoherent" is not a standard DT property. I couldn't find any > references to > it in the kernel as well. If we are introducing a new DT property for > non-coherent devices, > it should be added in DT bindings as well ? The dma-coherent is part of the core devicetree-spec, so I sent a patch adding dma-noncoherent [0] to the devicetree-spec mailing list yesterday as well. [0] https://www.spinics.net/lists/devicetree-spec/msg01053.html > > > */ > > bool of_dma_is_coherent(struct device_node *np) > > { > > struct device_node *node; > > + bool ret = false; > > > > if (IS_ENABLED(CONFIG_OF_DMA_DEFAULT_COHERENT)) > > - return true; > > + ret = true; > > > > node = of_node_get(np); > > > > while (node) { > > if (of_property_read_bool(node, "dma-coherent")) { > > - of_node_put(node); > > - return true; > > + ret = true; > > + break; > > + } > > + if (of_property_read_bool(node, "dma-noncoherent")) { > > + ret = false; > > + break; > > } > > node = of_get_next_dma_parent(node); > > } > > of_node_put(node); > > - return false; > > + return ret; > > } > > EXPORT_SYMBOL_GPL(of_dma_is_coherent); > > > > -- > > 2.35.1 > > > > >
