dmaengine: pl330: Add quirk 'arm,pl330-periph-burst'

This patch adds the qurik to use burst transfers only
for pl330 controller, even for request with a length of 1.

Although, the correct way should be: if the peripheral request
length is 1, the peripheral should use SINGLE request, and then
notify the dmac using SINGLE mode by src/dst_maxburst with 1.

For example, on the Rockchip SoCs, all the peripherals can use
SINGLE or BURST request by setting GRF registers. it is possible
that if these peripheral drivers are used only for Rockchip SoCs.
Unfortunately, it's not, such as dw uart, which is used so widely,
and we can't set src/dst_maxburst according to the SoCs' specific
to compatible with all the other SoCs.

So, for convenience, all the peripherals are set as BURST request
by default on the Rockchip SoCs. even for request with a length of 1.
the current pl330 driver will perform SINGLE transfer if the client's
maxburst is 1, which still should be working according to chapter 2.6.6
of datasheet which describe how DMAC performs SINGLE transfers for
a BURST request. Unfortunately, it's broken on the Rockchip SoCs,
which support only matching transfers, such as BURST transfer for
BURST request, SINGLE transfer for SINGLE request.

Finally, we add the quirk to specify pl330 to use burst transfers only.

Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Link: https://lore.kernel.org/r/1593439555-68130-5-git-send-email-sugar.zhang@rock-chips.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions