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>
diff --git a/bitbang_spi.c b/bitbang_spi.c
index f697f5a..fe85b60 100644
--- a/bitbang_spi.c
+++ b/bitbang_spi.c
@@ -53,6 +53,18 @@
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 @@
*/
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 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 @@
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;
}