From 97f362a718effa2c476490c5bc8b204c6de64913 Mon Sep 17 00:00:00 2001
From: Clyde Stubbs <2366188+clydebarrow@users.noreply.github.com>
Date: Mon, 28 Sep 2026 00:04:17 +1000
Subject: [PATCH] [mipi_spi] Fix reversion in dc/cs sequence for spi_16
 (#19745)

---
 esphome/components/mipi_spi/mipi_spi.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/esphome/components/mipi_spi/mipi_spi.h b/esphome/components/mipi_spi/mipi_spi.h
index 550e1998bb..e97b0e3a31 100644
--- a/esphome/components/mipi_spi/mipi_spi.h
+++ b/esphome/components/mipi_spi/mipi_spi.h
@@ -246,20 +246,18 @@ class MipiSpi : public display::Display,
       this->write_cmd_addr_data(8, 0x02, 24, cmd << 8, bytes, len);
       this->disable();
     } else if constexpr (BUS_TYPE == BUS_TYPE_OCTAL) {
-      // Toggle D/C only while holding the bus; on boards where D/C doubles as
-      // another bus signal, driving it while another device owns the bus
-      // corrupts that device's transfer.
       this->enable();
       this->dc_pin_->digital_write(false);
       this->write_cmd_addr_data(0, 0, 0, 0, &cmd, 1, 8);
       this->dc_pin_->digital_write(true);
-      this->disable();
+      // hold the bus between command and data to avoid a glitch on the D/C line
       if (len != 0) {
-        this->enable();
         this->write_cmd_addr_data(0, 0, 0, 0, bytes, len, 8);
-        this->disable();
       }
+      this->disable();
     } else if constexpr (BUS_TYPE == BUS_TYPE_SINGLE) {
+      // Toggle D/C only while holding the bus; works around a quirk in the CoreS3 and W5500 ethernet combination.
+      // See https://github.com/esphome/esphome/pull/18529
       this->enable();
       this->dc_pin_->digital_write(false);
       this->write_byte(cmd);
@@ -271,12 +269,14 @@ class MipiSpi : public display::Display,
         this->disable();
       }
     } else if constexpr (BUS_TYPE == BUS_TYPE_SINGLE_16) {
-      this->enable();
+      // DC must be stable before CS as the clock is gated by CS
       this->dc_pin_->digital_write(false);
+      this->enable();
       this->write_byte(cmd);
-      this->dc_pin_->digital_write(true);
       this->disable();
+      this->dc_pin_->digital_write(true);
       for (size_t i = 0; i != len; i++) {
+        // must enable and disable for each byte based on empirical testing
         this->enable();
         this->write_byte(0);
         this->write_byte(bytes[i]);