[U-Boot] [PATCH 1/6] Kconfig: Migrate BOUNCE_BUFFER

[Alexey Brodkin]

Hi Philipp,

> -----Original Message-----
> From: Philipp Tomsich [mailto:philipp.tomsich at theobroma-systems.com]
> Sent: Friday, November 30, 2018 2:40 PM
> To: u-boot at lists.denx.de
> Cc: Tom Rini <trini at konsulko.com>; Philipp Tomsich <philipp.tomsich at theobroma-systems.com>; Mario Six <mario.six at gdsys.cc>;
> Michal Simek <michal.simek at xilinx.com>; Simon Glass <sjg at chromium.org>; Masahiro Yamada
> <yamada.masahiro at socionext.com>; Alexey Brodkin <alexey.brodkin at synopsys.com>; Alex Kiernan <alex.kiernan at gmail.com>; Eric
> Nelson <eric at nelint.com>; Marek Vasut <marek.vasut at gmail.com>; Jörg Krause <joerg.krause at embedded.rocks>; Adam Ford
> <aford173 at gmail.com>; Stephen Warren <swarren at nvidia.com>; Angelo Dureghello <angelo at sysam.it>; Tuomas Tynkkynen
> <tuomas.tynkkynen at iki.fi>; Eugeniu Rosca <roscaeugeniu at gmail.com>
> Subject: [PATCH 1/6] Kconfig: Migrate BOUNCE_BUFFER
> 
> The bounce buffer is used by a few drivers (most of the MMC drivers)
> to overcome limitations in their respective DMA implementation.
> 
> This moves the configuration to Kconfig and makes it user-selectable
> (even though it will be a required feature to make those drivers
> work): the expected usage is for drivers depending on this to 'select'
> it unconditionally from their respective Kconfig.
> 
> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> 
> ---
> 
>  common/Kconfig               | 8 ++++++++
>  scripts/config_whitelist.txt | 1 -
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/common/Kconfig b/common/Kconfig
> index 57bd16d..f45e066 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -645,6 +645,14 @@ config DISPLAY_BOARDINFO_LATE
>  	  the relocation phase. The board function checkboard() is called to do
>  	  this.
> 
> +config BOUNCE_BUFFER
> +	bool "Include bounce buffer API"
> +	help
> +	  Some peripherals support DMA from a subset of physically
> +	  addressable memory only.  To support such peripherals, the
> +	  bounce buffer API uses a temporary buffer: it copies data
> +	  to/from DMA regions while managing cache operations.

IIRC I decided to use bounce buffer just to make sure data we pass to the DMA is
properly aligned. Not sure though if that's a valid use-case for it but if it is
IMHO it worth mentioning here in this help message.

-Alexey