From 8676830e61985e61286c494de957c57bdf610b9e Mon Sep 17 00:00:00 2001
From: michael <xiaoxufeng@espressif.com>
Date: Tue, 19 Jun 2018 20:38:17 +0800
Subject: [PATCH] fix(spi_master): allow to use cs_ena_pretrans in full duplex
 mode without command and address phases

---
 components/driver/spi_master.c                | 28 ++++++++++++-------
 .../api-reference/peripherals/spi_master.rst  |  2 ++
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/components/driver/spi_master.c b/components/driver/spi_master.c
index 4641e4bca..49b14b2a2 100644
--- a/components/driver/spi_master.c
+++ b/components/driver/spi_master.c
@@ -333,8 +333,7 @@ esp_err_t spi_bus_add_device(spi_host_device_t host, const spi_device_interface_
     SPI_CHECK(freecs!=NO_CS, "no free cs pins for host", ESP_ERR_NOT_FOUND);
     //The hardware looks like it would support this, but actually setting cs_ena_pretrans when transferring in full
     //duplex mode does absolutely nothing on the ESP32.
-    SPI_CHECK(dev_config->cs_ena_pretrans <= 1 || (dev_config->flags & SPI_DEVICE_HALFDUPLEX), "cs pretrans delay > 1 incompatible with full-duplex", ESP_ERR_INVALID_ARG);
-    SPI_CHECK( dev_config->cs_ena_pretrans != 1 || (dev_config->address_bits == 0 && dev_config->command_bits == 0) ||
+    SPI_CHECK( dev_config->cs_ena_pretrans <= 1 || (dev_config->address_bits == 0 && dev_config->command_bits == 0) ||
         (dev_config->flags & SPI_DEVICE_HALFDUPLEX), "In full-duplex mode, only support cs pretrans delay = 1 and without address_bits and command_bits", ESP_ERR_INVALID_ARG);
 
     duty_cycle = (dev_config->duty_cycle_pos==0? 128: dev_config->duty_cycle_pos);
@@ -711,17 +710,26 @@ static void SPI_MASTER_ISR_ATTR spi_intr(void *arg)
 
         //Configure bit sizes, load addr and command
         int cmdlen;
-        if ( trans->flags & SPI_TRANS_VARIABLE_CMD ) {
-            cmdlen = ((spi_transaction_ext_t*)trans)->command_bits;
-        } else {
-            cmdlen = dev->cfg.command_bits;
-        }
         int addrlen;
-        if ( trans->flags & SPI_TRANS_VARIABLE_ADDR ) {
-            addrlen = ((spi_transaction_ext_t*)trans)->address_bits;
+        if (!(dev->cfg.flags & SPI_DEVICE_HALFDUPLEX) && dev->cfg.cs_ena_pretrans != 0) {
+            /* The command and address phase is not compatible with cs_ena_pretrans
+             * in full duplex mode.
+             */
+            cmdlen = 0;
+            addrlen = 0;
         } else {
-            addrlen = dev->cfg.address_bits;
+            if (trans->flags & SPI_TRANS_VARIABLE_CMD) {
+                cmdlen = ((spi_transaction_ext_t *)trans)->command_bits;
+            } else {
+                cmdlen = dev->cfg.command_bits;
+            }
+            if (trans->flags & SPI_TRANS_VARIABLE_ADDR) {
+                addrlen = ((spi_transaction_ext_t *)trans)->address_bits;
+            } else {
+                addrlen = dev->cfg.address_bits;
+            }
         }
+
         host->hw->user1.usr_addr_bitlen=addrlen-1;
         host->hw->user2.usr_command_bitlen=cmdlen-1;
         host->hw->user.usr_addr=addrlen?1:0;
diff --git a/docs/en/api-reference/peripherals/spi_master.rst b/docs/en/api-reference/peripherals/spi_master.rst
index 3a526fbd5..bb09472ec 100644
--- a/docs/en/api-reference/peripherals/spi_master.rst
+++ b/docs/en/api-reference/peripherals/spi_master.rst
@@ -384,6 +384,8 @@ Known Issues
 2. Full duplex mode is not compatible with the *dummy bit workaround*, hence the frequency is limited. See :ref:`dummy
    bit speed-up workaround <dummy_bit_workaround>`.
 
+3. ``cs_ena_pretrans`` is not compatible with command, address phases in full duplex mode.
+
 
 Application Example
 -------------------