[PATCH 9/9] ARM: multi_v7_defconfig: Enable DMA for Renesas serial ports

[Arnd Bergmann]

On Tue, Jul 11, 2017 at 8:59 AM, Geert Uytterhoeven
<geert at linux-m68k.org> wrote:
> Hi Magnus,
>
> On Tue, Jul 11, 2017 at 5:38 AM, Magnus Damm <magnus.damm at gmail.com> wrote:
>> On Mon, Jul 10, 2017 at 10:28 PM, Geert Uytterhoeven

>> Since enabling DMA Engine still keeps PIO support around I wonder why
>> we need this Kconfig at all - other drivers seem to get by without
>> this kind of thing?
>> So in my opinion it would also be nice to get rid of SERIAL_SH_SCI_DMA
>> completely and reducing the number of special per-driver Kconfig
>> entries.
>
> In general, I would agree, and remove the option at the blimp of an eye.
> However, this driver is shared with H8/300 and SuperH.  While both could use
> DMA (but it's not supported by Linux yet), I don't know if they are willing to
> live with the increased static and dynamic memory footprint of SH_SCI DMA
> support.

One more thing: enabling the DMA support in the console driver generally
means you cannot use printk in the DMA driver anywhere that may be called
during printk(). Not sure if that is a concern here.

      Arnd