On Mon, Oct 15, 2018 at 12:36:36AM +0200, Wolfram Sang wrote:

On Sat, Oct 13, 2018 at 12:03:08AM +0900, Masahiro Yamada wrote:

quoted

host->chan_{rx,tx} represents the DMA capability of the platform.
Even if DMA is supported, there are cases where we want to use PIO,
for example, data length is short enough as commit 5f52c3552946
("mmc: tmio: use PIO for short transfers") mentioned.

Regarding the hardware control flow, we are interested in whether DMA
is currently enabled or not, instead of whether the platform has the
DMA capability.

Hence, the several conditionals in tmio_mmc_core.c end up with
checking host->chan_{rx,tx} and !host->force_pio. This is not nice.

Let's flip the flag host->force_pio into host->dma_on.

host->dma_on represents whether the DMA is currently enabled or not.
This flag is set false in the beginning of each command, then should
be set true by tmio_mmc_start_dma() when the DMA is turned on.

Signed-off-by: Masahiro Yamada <redacted>

I like it. Much easier to read!

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Tested on R-Car H3 ES1.0 and ES2.0, M3N, and H2. No regressions,
especially no performance regressions (since "when to enable DMA" code
was refactored).

Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

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