Re: [PATCH v8 07/10] i3c: master: Add driver for Cadence IP

[Arnd Bergmann]

On Wed, Oct 3, 2018 at 3:22 PM Boris Brezillon
<boris.brezillon@xxxxxxxxxxx> wrote:
>
> Add a driver for Cadence I3C master IP.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
> ---

> Changes in v7:
> - Fix readsl/writesl() usage
> - Add a depends on ARM || ARM64 || XTENSA to forbid selection of this
>   driver on platforms that are not implementing readsl/writesl

Most architectures include asm-generic/io.h, which contains a generic
implementation of readsl(). Maybe that #ifdef could be extended here?
I remember discussing this with you not so long ago, which led to
commit 0bbf47eab469 ("ia64: use asm-generic/io.h"). Do we have
a list of architectures that don't include asm-generic/io.h? Maybe
the 'depends on' could be for the set of architectures that fail here.

> +static void cdns_i3c_master_rd_from_rx_fifo(struct cdns_i3c_master *master,
> +                                           u8 *bytes, int nbytes)
> +{
> +       readsl(master->regs + RX_FIFO, bytes, nbytes / 4);
> +       if (nbytes & 3) {
> +               u32 tmp = __raw_readl(master->regs + RX_FIFO);
> +
> +               memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
> +       }
> +}

The __raw_readl() is probably correct here (I can't think of any
architecture on which it is not), but it still makes me feel uneasy
about possible endianess or other issues.

Maybe make this:?

        readsl(master->regs + RX_FIFO, &tmp, 1);


     Arnd