On 21.08.2024 15:10:58, Martin Jocić wrote: > > Several other driver first set a 64 bit mask and if this fails they set > > a 32 bit mask and then bail out, e.g.: [...] > As far as I can tell, the dynamic DMA mapping guide of the Kernel docs seems to > advise against this: > > From https://www.kernel.org/doc/html/next/core-api/dma-api-howto.html > > <begin quote> > The standard 64-bit addressing device would do something like this: > > dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)) > > dma_set_mask_and_coherent() never return fail when DMA_BIT_MASK(64). > Typical error code like: > > /* Wrong code */ > if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) > dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)) > > dma_set_mask_and_coherent() will never return failure when bigger than 32. > So typical code like: > > /* Recommended code */ > if (support_64bit) > dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); > else > dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); > <end quote> Thanks for looking it up and pointing out. > In Kvaser's case all CAN PCIe devices support 64-bit addressing. > > Should I still change the patch as per your suggestion? Use the original patch but please convert the ifdef into IS_ENABLED: if (IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung Nürnberg | Phone: +49-5121-206917-129 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
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