On Sat, Aug 15, 2015 at 10:16:03PM +0200, Arnd Bergmann wrote: > On Tuesday 11 August 2015 18:43:09 Leilk Liu wrote: > > @@ -359,9 +359,11 @@ static void mtk_spi_setup_dma_addr(struct spi_master *master, > > struct mtk_spi *mdata = spi_master_get_devdata(master); > > > > if (mdata->tx_sgl) > > - writel(cpu_to_le32(xfer->tx_dma), mdata->base + SPI_TX_SRC_REG); > > + writel((__force u32)cpu_to_le32(xfer->tx_dma), > > + mdata->base + SPI_TX_SRC_REG); > > if (mdata->rx_sgl) > > - writel(cpu_to_le32(xfer->rx_dma), mdata->base + SPI_RX_DST_REG); > > + writel((__force u32)cpu_to_le32(xfer->rx_dma), > > + mdata->base + SPI_RX_DST_REG); > > } > > > > This looks wrong: writel takes a CPU-endian argument, so the value returned > from cpu_to_le32() is not appropriate. > > The warning is correct, and you have to remove the cpu_to_le32() conversion > in order to get the driver to behave correctly when the kernel is built > as big-endian. Indeed, it's about time people started thinking more about the warnings and why we have coded things in the way we have. Look people. cpu_to_le32() takes a value in the CPU endian, and converts it to a little endian 32-bit number. See, the clue is in the name. All writel() implementations take a CPU number and write it in little endian format. Hence, writel() almost always uses cpu_to_le32() internally. Now think about what you're saying with "cpu_to_le32(cpu_to_le32())". It's utter rubbish, total crap. It's wrong no matter which way you look at it. We have le32_to_cpu() which does what it says on the tin. Same with be32_to_cpu() and cpu_to_be32(). Don't hack around this stuff with __force. If you're having to use __force to get rid of a warning here, you _ARE_ doing something wrong, no questions about that. __force in driver code is a definite sign that you are doing something wrong. Don't do it. Ask the question if you think you need it. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
