From 88c6b2ff6d9db41bbbbac445cf299c3fd8c49cab Mon Sep 17 00:00:00 2001
From: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Date: Thu, 29 Oct 2020 08:15:32 +0100
Subject: [PATCH] Improve FTDI communication in bitbang mode sub layer cut
 package in allowed size, so it's not mandatory to do this at openFPGALoader
 level. The only situation when the size is important is in read mode. So
 increase buffer size to reduce system calls.

---
 src/ftdiJtagBitbang.cpp | 32 +++++++++++++++++++++++++++-----
 src/ftdiJtagBitbang.hpp |  5 ++---
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/src/ftdiJtagBitbang.cpp b/src/ftdiJtagBitbang.cpp
index 340ebe4..1b66699 100644
--- a/src/ftdiJtagBitbang.cpp
+++ b/src/ftdiJtagBitbang.cpp
@@ -23,6 +23,7 @@
 #include <map>
 #include <vector>
 #include <string>
+#include <stdexcept>
 
 #include "ftdiJtagBitbang.hpp"
 #include "ftdipp_mpsse.hpp"
@@ -44,18 +45,38 @@ FtdiJtagBitBang::FtdiJtagBitBang(const FTDIpp_MPSSE::mpsse_bit_config &cable,
 			const jtag_pins_conf_t *pin_conf, string dev, const std::string &serial,
 			uint32_t clkHZ, bool verbose):
 			FTDIpp_MPSSE(cable, dev, serial, clkHZ, verbose), _bitmode(0),
-			_curr_tms(0)
+			_curr_tms(0), _rx_size(0)
 {
+	unsigned char *ptr;
+
 	_tck_pin = (1 << pin_conf->tck_pin);
 	_tms_pin = (1 << pin_conf->tms_pin);
 	_tdi_pin = (1 << pin_conf->tdi_pin);
 	_tdo_pin = (1 << pin_conf->tdo_pin);
 
-	_buffer_size = 512;  // TX Fifo size
+	/* store FTDI TX Fifo size */
+	if (_pid == 0x6001)  // FT232R
+		_rx_size = 256;
+	else if (_pid == 0x6015)  // FT231X
+		_rx_size = 512;
+	else
+		_rx_size = _buffer_size;
+
+	/* RX Fifo size (rx: USB -> FTDI)
+	 * is 128 or 256 Byte and MaxPacketSize ~= 64Byte
+	 * but we let subsystem (libftdi, libusb, linux)
+	 * sending with the correct size -> this reduce hierarchical calls
+	 */
+	_buffer_size = 4096;
+
+	/* _buffer_size has changed -> resize buffer */
+	ptr = (unsigned char *)realloc(_buffer, sizeof(char) * _buffer_size);
+	if (!ptr)
+		throw std::runtime_error("_buffer realloc failed\n");
+	_buffer = ptr;
 
 	setClkFreq(_clkHZ);
 
-	_buffer = (unsigned char *)realloc(_buffer, sizeof(char) * _buffer_size);
 	init(1, _tck_pin | _tms_pin | _tdi_pin, BITMODE_BITBANG);
 	setBitmode(BITMODE_BITBANG);
 }
@@ -134,10 +155,11 @@ int FtdiJtagBitBang::writeTMS(uint8_t *tms, int len, bool flush_buffer)
 int FtdiJtagBitBang::writeTDI(uint8_t *tx, uint8_t *rx, uint32_t len, bool end)
 {
 	uint32_t iter;
-	if (len * 2 + 1 < (uint32_t)_buffer_size) {
+	uint32_t xfer_size = (rx) ? _rx_size : _buffer_size;
+	if (len * 2 + 1 < xfer_size) {
 		iter = len;
 	} else {
-		iter = _buffer_size >> 1;  // two tx / bit
+		iter = xfer_size >> 1;  // two tx / bit
 		iter = (iter / 8) * 8;
 	}
 
diff --git a/src/ftdiJtagBitbang.hpp b/src/ftdiJtagBitbang.hpp
index 8d8a523..d067584 100644
--- a/src/ftdiJtagBitbang.hpp
+++ b/src/ftdiJtagBitbang.hpp
@@ -58,21 +58,20 @@ class FtdiJtagBitBang : public JtagInterface, private FTDIpp_MPSSE {
 	 */
 	int get_buffer_size() override { return _buffer_size/8/2; }
 
-	bool isFull() override { return _nb_bit == 8*get_buffer_size();}
+	bool isFull() override { return _num == 8*get_buffer_size();}
 
 	int flush() override;
 
  private:
 	int write(uint8_t *tdo, int nb_bit);
 	int setBitmode(uint8_t mode);
-	uint8_t *_in_buf;
 
 	uint8_t _bitmode;
 	uint8_t _tck_pin; /*!< tck pin: 1 << pin id */
 	uint8_t _tms_pin; /*!< tms pin: 1 << pin id */
 	uint8_t _tdo_pin; /*!< tdo pin: 1 << pin id */
 	uint8_t _tdi_pin; /*!< tdi pin: 1 << pin id */
-	int _nb_bit;
 	uint8_t _curr_tms;
+	int _rx_size;
 };
 #endif