[PATCH v4] spi: add spi_tegra driver

[Grant Likely]

On Wed, Sep 1, 2010 at 4:16 PM, Erik Gilling <konkers at android.com> wrote:
> v2 changes:
>  from Thierry Reding:
>    * add "select TEGRA_SYSTEM_DMA" to Kconfig
>  from Grant Likely:
>    * add oneline description to header
>    * inline references to DRIVER_NAME
>    * inline references to BUSY_TIMEOUT
>    * open coded bytes_per_word()
>    * spi_readl/writel -> spi_tegra_readl/writel
>    * move transfer validation to spi_tegra_transfer
>    * don't request_mem_region iomem as platform bus does that for us
>    * __exit -> __devexit
>
> v3 changes:
>  from Russell King:
>    * put request_mem_region back int
>  from Grant Likely:
>    * remove #undef DEBUG
>    * add SLINK_ to register bit defines
>    * remove unused bytes_per_word
>    * make spi_tegra_readl/writel static linine
>    * various refactoring for clarity
>    * mark err if BSY bit is not cleared after 1000 retries
>    * move spinlock to protect setting of RDY bit
>    * subsys_initcall -> module_init
>
> v3 changes:
>  from Grant Likely:
>    * update spi_tegra to use PTR_ERRless dma API
>
> Signed-off-by: Erik Gilling <konkers at android.com>
> Cc: Thierry Reding <thierry.reding at avionic-design.de>
> Cc: Grant Likely <grant.likely at secretlab.ca>
> Cc: Russell King <linux at arm.linux.org.uk>

Hi Erik,

Go ahead and add my Acked-by line and merge this via the tegra tree to
avoid ordering issues.  I also have a few more minor comments below.

g.

> +       /* FIXME: should probably control CS manually so that we can be sure
> +        * it does not go low between transfer and to support delay_usecs
> +        * correctly.
> +        */

Yes, you'll probably want to revisit this.  A lot of SPI hardware
doesn't understand that the actual transfer may be longer that the
data it immediately knows about.  Also, it is common to use GPIOs as
chip selects.

> +static void spi_tegra_cleanup(struct spi_device *spi)
> +{
> +       dev_dbg(&spi->dev, "cleanup\n");
> +}

Remove the empty hook

> +static int __init spi_tegra_probe(struct platform_device *pdev)
> +{
> +       struct spi_master       *master;
> +       struct spi_tegra_data   *tspi;
> +       struct resource         *r;
> +       int ret;
> +
> +       master = spi_alloc_master(&pdev->dev, sizeof *tspi);
> +       if (master == NULL) {
> +               dev_err(&pdev->dev, "master allocation failed\n");
> +               return -ENOMEM;
> +       }
> +
> +       /* the spi->mode bits understood by this driver: */
> +       master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
> +
> +       if (pdev->id != -1)
> +               master->bus_num = pdev->id;

even if pdev->id is -1, you probably want to set master->bus_num to is
so that a spi bus number can be dynamically assigned.