Adds SPI driver for Tiva (#568)

* Adds a SPI driver for tiva 123/129.
This driver does not yet support DMA and only supports single bit transfers.

* Fixes whitespace.

* fix hanging brace

* Fixes bugs in the tiva SPI driver.

* Fix comment

src/freertos_drivers/ti/TivaSPI.cxx

@@ -0,0 +1,167 @@
+/** \copyright
+ * Copyright (c) 2021, Balazs Racz
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are  permitted provided that the following conditions are met:
+ * 
+ *  - Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  - Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * \file TivaSPI.cxx
+ * This file implements a SPI device driver for Tiva (129).
+ *
+ * @author Balazs Racz
+ * @date 18 Aug 2021
+ */
+
+#include "TivaSPI.hxx"
+
+#include "inc/hw_memmap.h"
+#include "driverlib/sysctl.h"
+#include "driverlib/rom.h"
+#include "driverlib/rom_map.h"
+#include "driverlib/interrupt.h"
+
+/// One semaphore per peripheral.
+OSSem sem[4];
+
+TivaSPI::TivaSPI(const char *name, unsigned long base, uint32_t interrupt,
+    ChipSelectMethod cs_assert, ChipSelectMethod cs_deassert,
+    OSMutex *bus_lock,
+    size_t dma_threshold,
+    uint32_t dma_channel_index_tx,
+    uint32_t dma_channel_index_rx)
+    :  SPI(name, cs_assert, cs_deassert, bus_lock)
+    , base_(base)
+    , interrupt_(interrupt)
+    , dmaThreshold_(dma_threshold)
+    , dmaChannelIndexTx_(dma_channel_index_tx)
+    , dmaChannelIndexRx_(dma_channel_index_rx)
+{
+    uint32_t p = 0;
+    switch(base_) {
+    case SSI0_BASE:
+        p = SYSCTL_PERIPH_SSI0;
+        sem_ = sem + 0;
+        break;
+    case SSI1_BASE:
+        p = SYSCTL_PERIPH_SSI1;
+        sem_ = sem + 1;
+        break;
+    case SSI2_BASE:
+        p = SYSCTL_PERIPH_SSI2;
+        sem_ = sem + 2;
+        break;
+    case SSI3_BASE:
+        p = SYSCTL_PERIPH_SSI3;
+        sem_ = sem + 3;
+        break;
+    default:
+        DIE("Unknown SPI peripheral.");
+    }
+    MAP_SysCtlPeripheralEnable(p);
+    MAP_SysCtlPeripheralReset(p);
+
+    update_configuration();
+}
+
+TivaSPI::~TivaSPI()
+{
+}
+
+void TivaSPI::enable()
+{
+}
+
+void TivaSPI::disable()
+{
+}
+
+/** Update the configuration of the bus.
+ * @return >= 0 upon success, -errno upon failure
+ */
+int TivaSPI::update_configuration()
+{
+    unsigned long new_mode;
+
+    switch (mode_)
+    {
+        default:
+        case SPI_MODE_0:
+            new_mode = SSI_FRF_MOTO_MODE_0;
+            break;
+        case SPI_MODE_1:
+            new_mode = SSI_FRF_MOTO_MODE_1;
+            break;
+        case SPI_MODE_2:
+            new_mode = SSI_FRF_MOTO_MODE_2;
+            break;
+        case SPI_MODE_3:
+            new_mode = SSI_FRF_MOTO_MODE_3;
+            break;
+    }
+
+    HASSERT(bitsPerWord <= 16);
+
+    uint32_t clock = cm3_cpu_clock_hz;
+    /* The SPI peripheral only supoprts certain frequencies and driverlib does
+     * not properly round down. We can do some math to make sure that driverlib
+     * makes the correct selection.
+     */
+    if (speedHz > (clock / 2))
+    {
+        speedHz = clock / 2;
+    }
+    else if ((clock % speedHz) != 0)
+    {
+        speedHz = clock / ((clock / speedHz) + 1);
+    }
+
+    MAP_SSIDisable(base_);
+    MAP_SSIConfigSetExpClk(base_, clock, new_mode, SSI_MODE_MASTER,
+                           speedHz, bitsPerWord);
+    MAP_IntPrioritySet(interrupt_, configKERNEL_INTERRUPT_PRIORITY);
+    MAP_IntEnable(interrupt_);
+    MAP_SSIEnable(base_);
+
+    // these values are used to quickly program instance local configuration
+    // settings
+    spiCr0_ = HWREG(base_ + SSI_O_CR0);
+    spiCr1_ = HWREG(base_ + SSI_O_CR1);
+    spiPrescaler_ = HWREG(base_ + SSI_O_CPSR);
+
+    return 0;
+}
+
+/** Configure a DMA transaction.
+ * @param msg message to transact.
+ */
+__attribute__((optimize("-O3")))
+void TivaSPI::config_dma(struct spi_ioc_transfer *msg)
+{
+    DIE("DMA transfer is not yet implemented.");
+}
+
+__attribute__((optimize("-O3")))
+void TivaSPI::interrupt_handler()
+{
+    DIE("SPI interrupt is not yet implemented.");
+}
+