dmaengine: dw-edma: Snapshot the v0 interrupt status once per handler pass

The v0 interrupt handler reads the interrupt status register twice per
invocation, once through the DONE accessor and once through the ABORT
accessor, although both fields live in the same 32-bit register. On
remote setups (dw-edma-pcie) each read is a non-posted round trip across
the PCIe link costing on the order of a microsecond, and with one
completion interrupt per element the duplicate adds up. As an example,
profiling the R-Car S4 remote path put the handler at ~7us per
invocation, dominated by such reads.

Read the register once and derive the DONE and ABORT views from the
snapshot. No abort is lost to this because the pass only clears status
bits it observed, so an abort raised after the snapshot keeps its status
and its own interrupt delivery brings it to the next pass. An abort on
an observed channel cannot race the clear either. Software can restart
the halted channel only after abort() runs, and abort() is called after
dw_edma_v0_core_clear_abort_int().

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Link: https://patch.msgid.link/20260717180639.2643243-9-den@valinux.co.jp
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions