From: Arnd Bergmann <arnd@arndb.de>
To: Leilk Liu <leilk.liu@mediatek.com>
Cc: Mark Brown <broonie@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Sascha Hauer <s.hauer@pengutronix.de>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-spi@vger.kernel.org, linux-mediatek@lists.infradead.org
Subject: Re: [PATCH] spi: Mediatek: fix endian warnings
Date: Sat, 15 Aug 2015 22:16:03 +0200
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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.

	Arnd
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