[spi_device] Latch flip event only when active
Problem:
`flip` occurs regardless of the buffer's active state. Buffer is
active only when the read command sends output to the host system.
`flip` sees the address being latched while address is shifted in to
the register. It causes premature flip event, which in turn results
in the incorrect watermark event.
Revised the `flip` logic to latch only when the read buffer manager is
active.
Signed-off-by: Eunchan Kim <eunchan@opentitan.org>
diff --git a/hw/ip/spi_device/rtl/spid_readbuffer.sv b/hw/ip/spi_device/rtl/spid_readbuffer.sv
index c781838..cc4a14c 100644
--- a/hw/ip/spi_device/rtl/spid_readbuffer.sv
+++ b/hw/ip/spi_device/rtl/spid_readbuffer.sv
@@ -124,7 +124,7 @@
logic flip_q;
always_ff @(posedge clk_i or negedge sys_rst_ni) begin
if (!sys_rst_ni) flip_q <= 1'b 0;
- else flip_q <= flip;
+ else if (active) flip_q <= flip;
end
assign event_flip_o = active && flip && !flip_q;
