Change in flashrom[master]: ft2232_spi.c: release I/Os on shutdown

[Edward O'Callaghan (Code Review)]

Edward O'Callaghan has submitted this change. ( https://review.coreboot.org/c/flashrom/+/49632 )

Change subject: ft2232_spi.c: release I/Os on shutdown
......................................................................

ft2232_spi.c: release I/Os on shutdown

Reset FTDI I/O pins to high-Z (input) when shutting down. This allows
other devices to use the SPI bus without having to disconnect the
programmer.

This change will introduce a backward incompatibility in the case where
a user is relying on the state of FTDI outputs post-programming (eg. to
disallow another device from driving CS low).

However, there are likely more cases where releasing the SPI bus is the
correct thing to do.

Signed-off-by: Alan Green 
Change-Id: I9fae55e532595752983f55fac2298f81699dbe5b
Reviewed-on: https://review.coreboot.org/c/flashrom/+/49632
Reviewed-by: Edward O'Callaghan 
Reviewed-by: Angel Pons 
Tested-by: build bot (Jenkins) 
---
M ft2232_spi.c
1 file changed, 25 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Angel Pons: Looks good to me, but someone else must approve
  Edward O'Callaghan: Looks good to me, approved

diff --git a/ft2232_spi.c b/ft2232_spi.c
index 65ff449..c963a45 100644
--- a/ft2232_spi.c
+++ b/ft2232_spi.c
@@ -159,6 +159,30 @@
    return 0;
 }

+static int ft2232_shutdown(void *data)
+{
+	int f;
+	struct ftdi_context *ftdic = (struct ftdi_context *) data;
+	unsigned char buf[3];
+
+	msg_pdbg("Releasing I/Os\n");
+	buf[0] = SET_BITS_LOW;
+	buf[1] = 0; /* Output byte ignored */
+	buf[2] = 0; /* Pin direction: all inputs */
+	if (send_buf(ftdic, buf, 3)) {
+		msg_perr("Unable to set pins back inputs: (%s)\n",
+		         ftdi_get_error_string(ftdic));
+	}
+
+	if ((f = ftdi_usb_close(ftdic)) < 0) {
+		msg_perr("Unable to close FTDI device: %d (%s)\n", f,
+		         ftdi_get_error_string(ftdic));
+		return f;
+	}
+
+	return 0;
+}
+
 static int ft2232_spi_send_command(const struct flashctx *flash,
    			   unsigned int writecnt, unsigned int readcnt,
    			   const unsigned char *writearr,
@@ -453,6 +477,7 @@
    	goto ftdi_err;
    }

+	register_shutdown(ft2232_shutdown, ftdic);
    register_spi_master(&spi_master_ft2232);

return 0;