SPI bitbanging: request/release bus

SPI bitbanging on devices which speak SPI natively has a dual-use
problem: We need to shut down normal SPI operations to do the bitbanging
ourselves. Once we're done, it makes a lot of sense to reenable "normal"
SPI operations again. Add request_bus/release_bus functions to struct
bitbang_spi_master.
Add a bitbang shutdown function (not used yet).
Change MCP SPI and Intel NIC SPI to use the new request/release bus
infrastructure.
Cosmetic changes to a few error messages (80 column limit).

There are multiple possible strategies for bus request/release:
- Request at the start of a SPI command, release immediately afterwards.
- Request at the start of a SPI multicommand, release once all commands
of the multicommand are done.
- Request on programmer init, release on shutdown.
Each strategy has its own advantages. For now, we will stay with the
first strategy which worked fine so far.

Corresponding to flashrom svn r1171.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>

bitbang_spi.c

@@ -53,6 +53,18 @@ static int bitbang_spi_get_miso(void)
 	return bitbang_spi_master->get_miso();
 }
 
+static void bitbang_spi_request_bus(void)
+{
+	if (bitbang_spi_master->request_bus)
+		bitbang_spi_master->request_bus();
+}
+
+static void bitbang_spi_release_bus(void)
+{
+	if (bitbang_spi_master->release_bus)
+		bitbang_spi_master->release_bus();
+}
+
 int bitbang_spi_init(const struct bitbang_spi_master *master, int halfperiod)
 {
 	/* BITBANG_SPI_INVALID is 0, so if someone forgot to initialize ->type,
@@ -61,19 +73,44 @@ int bitbang_spi_init(const struct bitbang_spi_master *master, int halfperiod)
 	 */
 	if (!master || master->type == BITBANG_SPI_INVALID || !master->set_cs ||
 	    !master->set_sck || !master->set_mosi || !master->get_miso) {
-		msg_perr("Incomplete bitbanging SPI master setting! Please "
-			 "report a bug at flashrom@flashrom.org\n");
+		msg_perr("Incomplete SPI bitbang master setting!\n"
+			 "Please report a bug at flashrom@flashrom.org\n");
+		return 1;
+	}
+	if (bitbang_spi_master) {
+		msg_perr("SPI bitbang master already initialized!\n"
+			 "Please report a bug at flashrom@flashrom.org\n");
 		return 1;
 	}
+
 	bitbang_spi_master = master;
 	bitbang_spi_half_period = halfperiod;
 
+	/* FIXME: Run bitbang_spi_request_bus here or in programmer init? */
 	bitbang_spi_set_cs(1);
 	bitbang_spi_set_sck(0);
 	bitbang_spi_set_mosi(0);
 	return 0;
 }
 
+int bitbang_spi_shutdown(const struct bitbang_spi_master *master)
+{
+	if (!bitbang_spi_master) {
+		msg_perr("Shutting down an uninitialized SPI bitbang master!\n"
+			 "Please report a bug at flashrom@flashrom.org\n");
+		return 1;
+	}
+	if (master != bitbang_spi_master) {
+		msg_perr("Shutting down a mismatched SPI bitbang master!\n"
+			 "Please report a bug at flashrom@flashrom.org\n");
+		return 1;
+	}
+
+	/* FIXME: Run bitbang_spi_release_bus here or per command? */
+	bitbang_spi_master = NULL;
+	return 0;
+}
+
 static uint8_t bitbang_spi_readwrite_byte(uint8_t val)
 {
 	uint8_t ret = 0;
@@ -96,6 +133,11 @@ int bitbang_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 {
 	int i;
 
+	/* FIXME: Run bitbang_spi_request_bus here or in programmer init?
+	 * Requesting and releasing the SPI bus is handled in here to allow the
+	 * programmer to use its own SPI engine for native accesses.
+	 */
+	bitbang_spi_request_bus();
 	bitbang_spi_set_cs(0);
 	for (i = 0; i < writecnt; i++)
 		bitbang_spi_readwrite_byte(writearr[i]);
@@ -105,6 +147,8 @@ int bitbang_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 	programmer_delay(bitbang_spi_half_period);
 	bitbang_spi_set_cs(1);
 	programmer_delay(bitbang_spi_half_period);
+	/* FIXME: Run bitbang_spi_release_bus here or in programmer init? */
+	bitbang_spi_release_bus();
 
 	return 0;
 }

mcp6x_spi.c

@@ -66,18 +66,9 @@ static void mcp6x_release_spibus(void)
 
 static void mcp6x_bitbang_set_cs(int val)
 {
-	/* Requesting and releasing the SPI bus is handled in here to allow the
-	 * chipset to use its own SPI engine for native reads.
-	 */
-	if (val == 0)
-		mcp6x_request_spibus();
-
 	mcp_gpiostate &= ~(1 << MCP6X_SPI_CS);
 	mcp_gpiostate |= (val << MCP6X_SPI_CS);
 	mmio_writeb(mcp_gpiostate, mcp6x_spibar + 0x530);
-
-	if (val == 1)
-		mcp6x_release_spibus();
 }
 
 static void mcp6x_bitbang_set_sck(int val)
@@ -106,6 +97,8 @@ static const struct bitbang_spi_master bitbang_spi_master_mcp6x = {
 	.set_sck = mcp6x_bitbang_set_sck,
 	.set_mosi = mcp6x_bitbang_set_mosi,
 	.get_miso = mcp6x_bitbang_get_miso,
+	.request_bus = mcp6x_request_spibus,
+	.release_bus = mcp6x_release_spibus,
 };
 
 int mcp6x_spi_init(int want_spi)

nicintel_spi.c

@@ -91,20 +91,10 @@ static void nicintel_bitbang_set_cs(int val)
 {
 	uint32_t tmp;
 
-	/*
-	 * Requesting and releasing the SPI bus is handled in here to allow
-	 * the chipset to use its own SPI engine for native reads.
-	 */
-	if (val == 0)
-		nicintel_request_spibus();
-
 	tmp = pci_mmio_readl(nicintel_spibar + FLA);
 	tmp &= ~(1 << FL_CS);
 	tmp |= (val << FL_CS);
 	pci_mmio_writel(tmp,  nicintel_spibar + FLA);
-
-	if (val == 1)
-		nicintel_release_spibus();
 }
 
 static void nicintel_bitbang_set_sck(int val)
@@ -142,6 +132,8 @@ static const struct bitbang_spi_master bitbang_spi_master_nicintel = {
 	.set_sck = nicintel_bitbang_set_sck,
 	.set_mosi = nicintel_bitbang_set_mosi,
 	.get_miso = nicintel_bitbang_get_miso,
+	.request_bus = nicintel_request_spibus,
+	.release_bus = nicintel_release_spibus,
 };
 
 int nicintel_spi_init(void)

programmer.h

@@ -131,6 +131,8 @@ struct bitbang_spi_master {
 	void (*set_sck) (int val);
 	void (*set_mosi) (int val);
 	int (*get_miso) (void);
+	void (*request_bus) (void);
+	void (*release_bus) (void);
 };
 
 #if CONFIG_INTERNAL == 1
@@ -443,6 +445,7 @@ int mcp6x_spi_init(int want_spi);
 
 /* bitbang_spi.c */
 int bitbang_spi_init(const struct bitbang_spi_master *master, int halfperiod);
+int bitbang_spi_shutdown(const struct bitbang_spi_master *master);
 int bitbang_spi_send_command(unsigned int writecnt, unsigned int readcnt, const unsigned char *writearr, unsigned char *readarr);
 int bitbang_spi_read(struct flashchip *flash, uint8_t *buf, int start, int len);
 int bitbang_spi_write_256(struct flashchip *flash, uint8_t *buf, int start, int len);