atmel_spi: support zero length transfer

[linux-2.6-omap-h63xx.git] / drivers / spi / atmel_spi.c

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index 293b7cab3e57021afcfeddcd2a5b007fbfba229a..02c8e305b14fd783e3b94a71d3c8b4d9c4ed9c68 100644 (file)
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -87,6 +87,16 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
        unsigned gpio = (unsigned) spi->controller_data;
        unsigned active = spi->mode & SPI_CS_HIGH;
        u32 mr;
+       int i;
+       u32 csr;
+       u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0;
+
+       /* Make sure clock polarity is correct */
+       for (i = 0; i < spi->master->num_chipselect; i++) {
+               csr = spi_readl(as, CSR0 + 4 * i);
+               if ((csr ^ cpol) & SPI_BIT(CPOL))
+                       spi_writel(as, CSR0 + 4 * i, csr ^ SPI_BIT(CPOL));
+       }
 
        mr = spi_readl(as, MR);
        mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);
@@ -606,7 +616,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
                return -ESHUTDOWN;
 
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
-               if (!(xfer->tx_buf || xfer->rx_buf)) {
+               if (!(xfer->tx_buf || xfer->rx_buf) && xfer->len) {
                        dev_dbg(&spi->dev, "missing rx or tx buf\n");
                        return -EINVAL;
                }
@@ -853,3 +863,4 @@ module_exit(atmel_spi_exit);
 MODULE_DESCRIPTION("Atmel AT32/AT91 SPI Controller driver");
 MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:atmel_spi");