pd: hoho: mcdp28x0 serial driver.

Add initial serial driver for mdcp2850 dp->hdmi converter.  Driver
implements 'get information' (cmd:0x40) to provide rudimentary method
to test mcdp for functionality and assert GPIO if successful.

Future CLs may expose more serial functionality if necessary.

Signed-off-by: Todd Broch <tbroch@chromium.org>

BRANCH=samus
BUG=chrome-os-partner:34122
TEST=manual, when compiles with #define MCDP_DEBUG see successful
serial communication and result from get info.

  buf:[00]0x04 [01]0x40 [02]0x00 [03]0xbc
  ...
  buf:[00]0x0f [01]0x40 [02]0x00 [03]0x0e
      [04]0x00 [05]0x01 [06]0x01 [07]0x00
      [08]0x00 [09]0x00 [10]0x00 [11]0x00
      [12]0x00 [13]0x00
  family:000e chipid:0001 irom:1.0.0 fw:0.0.0

Change-Id: I35f9d9b0437633d1bd6a6c9fa14413bedb12f5c2
Reviewed-on: https://chromium-review.googlesource.com/235930
Trybot-Ready: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Commit-Queue: Todd Broch <tbroch@chromium.org>

1 files changed, 149 insertions, 0 deletions

diff --git a/driver/mcdp28x0.c b/driver/mcdp28x0.c
new file mode 100644
index 0000000000..de334b5c59
--- /dev/null
+++ b/driver/mcdp28x0.c
@@ -0,0 +1,149 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Megachips DisplayPort to HDMI protocol converter / level shifter driver.
+ */
+
+#include "config.h"
+#include "console.h"
+#include "common.h"
+#include "mcdp28x0.h"
+#include "timer.h"
+#include "usart-stm32f0.h"
+#include "util.h"
+
+#define CPRINTF(format, args...) cprintf(CC_USBPD, format, ## args)
+
+#undef MCDP_DEBUG
+
+#ifdef MCDP_DEBUG
+static inline void print_buffer(uint8_t *buf, int cnt)
+{
+	int i;
+	CPRINTF("buf:");
+	for (i = 0; i < cnt; i++) {
+		if (i && !(i % 4))
+			CPRINTF("\n    ");
+		CPRINTF("[%02d]0x%02x ", i, buf[i]);
+	}
+	CPRINTF("\n");
+}
+#else
+static inline void print_buffer(uint8_t *buf, int cnt) {}
+#endif
+
+USART_CONFIG(usart_mcdp, CONFIG_MCDP28X0, 115200, MCDP_INBUF_MAX,
+	     MCDP_OUTBUF_MAX, NULL, NULL);
+
+/**
+ * Compute checksum.
+ *
+ * @msg message bytes to compute checksum on.
+ * @cnt count of message bytes.
+ * @return partial checksum.
+ */
+static uint8_t compute_checksum(const uint8_t *msg, int cnt)
+{
+	int i;
+	/* 1st byte (not in msg) is always cnt + 2, so seed chksum with that */
+	uint8_t chksum = cnt + 2;
+
+	for (i = 0; i < cnt; i++)
+		chksum += msg[i];
+	return ~chksum + 1;
+}
+
+/**
+ * transmit message over serial
+ *
+ * Packet consists of:
+ *   msg[0]     == length including this byte + cnt + chksum
+ *   msg[1]     == 1st message byte
+ *   msg[cnt+1] == last message byte
+ *   msg[cnt+2] == checksum
+ *
+ * @msg message bytes
+ * @cnt count of message bytes
+ * @return zero if success, error code otherwise
+ */
+static int tx_serial(const uint8_t *msg, int cnt)
+{
+	uint8_t out = cnt + 2;
+	uint8_t chksum = compute_checksum(msg, cnt);
+
+	if (out_stream_write(&usart_mcdp.out, &out, 1) != 1)
+		return EC_ERROR_UNKNOWN;
+
+	if (out_stream_write(&usart_mcdp.out, msg, cnt) != cnt)
+		return EC_ERROR_UNKNOWN;
+
+	if (out_stream_write(&usart_mcdp.out, &chksum, 1) != 1)
+		return EC_ERROR_UNKNOWN;
+
+	print_buffer(usart_mcdp_tx_buffer, cnt + 2);
+
+	return EC_SUCCESS;
+}
+
+/**
+ * receive message over serial
+ *
+ * @msg pointer to buffer to read message into
+ * @cnt count of message bytes
+ * @return zero if success, error code otherwise
+ */
+static int rx_serial(uint8_t *msg, int cnt)
+{
+	size_t read;
+	int retry = 2;
+
+	read = in_stream_read(&usart_mcdp.in, msg, cnt);
+	while ((read < cnt) && retry) {
+		usleep(100*MSEC);
+		read += in_stream_read(&usart_mcdp.in, msg + read,
+				       cnt - read);
+		retry--;
+	}
+
+	print_buffer(msg, cnt);
+
+	return !(read == cnt);
+}
+
+void mcdp_enable(void)
+{
+	usart_init(&usart_mcdp);
+}
+
+void mcdp_disable(void)
+{
+	usart_shutdown(&usart_mcdp);
+}
+
+int mcdp_get_info(struct mcdp_info  *info)
+{
+	uint8_t inbuf[MCDP_RSP_LEN(MCDP_LEN_GETINFO)];
+	const uint8_t msg[2] = {MCDP_CMD_GETINFO, 0x00}; /* cmd + msg type */
+
+	if (tx_serial(msg, sizeof(msg)))
+		return EC_ERROR_UNKNOWN;
+
+	if (rx_serial(inbuf, sizeof(inbuf)))
+		return EC_ERROR_UNKNOWN;
+
+	/* check length & returned command ... no checksum provided */
+	if (((inbuf[0] - 1) != sizeof(inbuf)) ||
+	    (inbuf[1] != MCDP_CMD_GETINFO))
+		return EC_ERROR_UNKNOWN;
+
+	memcpy(info, &inbuf[2], MCDP_LEN_GETINFO);
+
+#ifdef MCDP_DEBUG
+	CPRINTF("family:%04x chipid:%04x irom:%d.%d.%d fw:%d.%d.%d\n",
+		MCDP_FAMILY(info->family), MCDP_CHIPID(info->chipid),
+		info->irom.major, info->irom.minor, info->irom.build,
+		info->fw.major, info->fw.minor, info->fw.build);
+#endif
+	return EC_SUCCESS;
+}