On s390 systems (aka mainframes), it has classic channel devices for networking and permanent storage that are currently even more common than PCI devices. Hence it could have a fully functional s390 kernel with CONFIG_PCI=n, then the relevant iomem mapping functions [including ioremap(), devm_ioremap(), etc.] are not available. In LKP error report at below on s390: ------ ld: kernel/dma/coherent.o: in function `dma_init_coherent_memory': coherent.c:(.text+0x102): undefined reference to `memremap' ld: coherent.c:(.text+0x226): undefined reference to `memunmap' ld: kernel/dma/coherent.o: in function `dma_declare_coherent_memory': coherent.c:(.text+0x8b8): undefined reference to `memunmap' ld: kernel/dma/coherent.o: in function `dma_release_coherent_memory': coherent.c:(.text+0x9aa): undefined reference to `memunmap' ------ In the config file, several Kconfig options are: ------ '# CONFIG_PCI is not set' CONFIG_OF_EARLY_FLATTREE=y CONFIG_DMA_DECLARE_COHERENT=y ------ So, enabling OF_EARLY_FLATTREE will select DMA_DECLARE_COHERENT and cause above building errors even though they are not needed because CONFIG_PCI is disabled. Here let OF_EARLY_FLATTREE depend on HAS_IOMEM so that it won't be built to cause compiling error if PCI is unset. Reported-by: kernel test robot <lkp@xxxxxxxxx> Closes: https://lore.kernel.org/oe-kbuild-all/202306211329.ticOJCSv-lkp@xxxxxxxxx/ Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> Cc: Rob Herring <robh+dt@xxxxxxxxxx> Cc: Frank Rowand <frowand.list@xxxxxxxxx> Cc: devicetree@xxxxxxxxxxxxxxx --- drivers/of/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig index e40f10bf2ba4..da9826accb1b 100644 --- a/drivers/of/Kconfig +++ b/drivers/of/Kconfig @@ -55,7 +55,7 @@ config OF_FLATTREE config OF_EARLY_FLATTREE bool - select DMA_DECLARE_COHERENT if HAS_DMA + select DMA_DECLARE_COHERENT if HAS_DMA && HAS_IOMEM select OF_FLATTREE config OF_PROMTREE -- 2.34.1
