libhw: rp2040_hwspi: Add more config knobs

2 files changed, 34 insertions, 11 deletions

diff --git a/libhw/rp2040_hwspi.c b/libhw/rp2040_hwspi.c
index ac46451..8dd49d6 100644
--- a/libhw/rp2040_hwspi.c
+++ b/libhw/rp2040_hwspi.c
@@ -18,6 +18,8 @@
 #define IMPLEMENTATION_FOR_LIBHW_RP2040_HWSPI_H YES
 #include <libhw/rp2040_hwspi.h>
 
+#include <libhw/generic/alarmclock.h>
+
 #include "config.h"
 
 #ifndef CONFIG_RP2040_SPI_DEBUG
@@ -39,6 +41,8 @@ void _rp2040_hwspi_init(struct rp2040_hwspi *self,
                         enum rp2040_hwspi_instance inst_num,
                         enum spi_mode mode,
                         uint baudrate_hz,
+                        uint64_t min_delay_ns,
+                        uint8_t bogus_data,
                         uint pin_miso,
                         uint pin_mosi,
                         uint pin_clk,
@@ -100,9 +104,12 @@ void _rp2040_hwspi_init(struct rp2040_hwspi *self,
 	gpio_set_dir(pin_cs, GPIO_OUT);
 	gpio_put(pin_cs, 1);
 
-	/* Return.  */
+	/* Initialize self.  */
 	self->inst = inst;
+	self->min_delay_ns = min_delay_ns;
+	self->bogus_data = bogus_data;
 	self->pin_cs = pin_cs;
+	self->dead_until_ns = 0;
 }
 
 static void rp2040_hwspi_readwritev(struct rp2040_hwspi *self, const struct duplex_iovec *iov, int iovcnt) {
@@ -113,6 +120,9 @@ static void rp2040_hwspi_readwritev(struct rp2040_hwspi *self, const struct dupl
 	assert(iov);
 	assert(iovcnt);
 
+	uint64_t now = LO_CALL(bootclock, get_time_ns);
+	if (now < self->dead_until_ns)
+		sleep_until_ns(self->dead_until_ns);
 	gpio_put(self->pin_cs, 0);
 	/* TODO: Replace blocking reads+writes with DMA.  */
 	for (int i = 0; i < iovcnt; i++) {
@@ -121,9 +131,10 @@ static void rp2040_hwspi_readwritev(struct rp2040_hwspi *self, const struct dupl
 		else if (iov[i].iov_write_src)
 			spi_write_blocking(inst, iov[i].iov_write_src, iov[i].iov_len);
 		else if (iov[i].iov_read_dst)
-			spi_read_blocking(inst, 0, iov[i].iov_read_dst, iov[i].iov_len);
+			spi_read_blocking(inst, self->bogus_data, iov[i].iov_read_dst, iov[i].iov_len);
 		else
 			assert_notreached("duplex_iovec is neither read nor write");
 	}
 	gpio_put(self->pin_cs, 1);
+	self->dead_until_ns = LO_CALL(bootclock, get_time_ns) + self->min_delay_ns;
 }
diff --git a/libhw/rp2040_include/libhw/rp2040_hwspi.h b/libhw/rp2040_include/libhw/rp2040_hwspi.h
index a1d85d4..fef1dbd 100644
--- a/libhw/rp2040_include/libhw/rp2040_hwspi.h
+++ b/libhw/rp2040_include/libhw/rp2040_hwspi.h
@@ -20,9 +20,14 @@ enum rp2040_hwspi_instance {
 
 struct rp2040_hwspi {
 	BEGIN_PRIVATE(LIBHW_RP2040_HWSPI_H)
+	/* const */
 	LM_IF(IS_IMPLEMENTATION_FOR(LIBHW_RP2040_HWSPI_H))(spi_inst_t)(void)    *inst;
+	uint64_t        min_delay_ns;
+	uint8_t         bogus_data;
+	uint            pin_cs;
 
-	uint    pin_cs;
+	/* mutable */
+	uint64_t        dead_until_ns;
 	END_PRIVATE(LIBHW_RP2040_HWSPI_H)
 };
 LO_IMPLEMENTATION_H(io_duplex_readwriter, struct rp2040_hwspi, rp2040_hwspi)
@@ -31,14 +36,17 @@ LO_IMPLEMENTATION_H(spi, struct rp2040_hwspi, rp2040_hwspi)
 /**
  * Initialize an instance of `struct rp2040_hwspi`.
  *
- * @param self     : struct rp2040_hwspi        : the structure to initialize
- * @param name     : char *                     : a name for the SPI port; to include in the bininfo
- * @param inst_num : enum rp2040_hwspi_instance : the PL220 instance number; RP2040_HWSPI_{0,1}
- * @param mode     : enum spi_mode              : the SPI mode; SPI_MODE_{0..3}
- * @param pin_miso : uint                       : pin number; 0, 4, 16, or 20 for _HWSPI_0; 8, 12, 24, or 28 for _HWSPI_1
- * @param pin_mosi : uint                       : pin number; 3, 7, 19, or 23 for _HWSPI_0; 11, 15, or 27 for _HWSPI_1
- * @param pin_clk  : uint                       : pin number; 2, 6, 18, or 22 for _HWSPI_0; 10, 14, or 26 for _HWSPI_1
- * @param pin_cs   : uint                       : pin number; any unused GPIO pin
+ * @param self        : struct rp2040_hwspi        : the structure to initialize
+ * @param name        : char *                     : a name for the SPI port; to include in the bininfo
+ * @param inst_num    : enum rp2040_hwspi_instance : the PL220 instance number; RP2040_HWSPI_{0,1}
+ * @param mode        : enum spi_mode              : the SPI mode; SPI_MODE_{0..3}
+ * @param baudrate_hz : uint                       : baudrate in Hz
+ * @param min_delay_ns: uint64_t                   : minimum time for pin_cs to be high between messages
+ * @param bogus_data  : uint8_t                    : bogus data to write when .iov_write_src is NULL
+ * @param pin_miso    : uint                       : pin number; 0, 4, 16, or 20 for _HWSPI_0; 8, 12, 24, or 28 for _HWSPI_1
+ * @param pin_mosi    : uint                       : pin number; 3, 7, 19, or 23 for _HWSPI_0; 11, 15, or 27 for _HWSPI_1
+ * @param pin_clk     : uint                       : pin number; 2, 6, 18, or 22 for _HWSPI_0; 10, 14, or 26 for _HWSPI_1
+ * @param pin_cs      : uint                       : pin number; any unused GPIO pin
  *
  * There is no bit-order argument; the RP2040's hardware SPI always
  * uses MSB-first bit order.
@@ -67,6 +75,7 @@ LO_IMPLEMENTATION_H(spi, struct rp2040_hwspi, rp2040_hwspi)
  */
 #define rp2040_hwspi_init(self, name,                                    \
                           inst_num, mode, baudrate_hz,                   \
+                          min_delay_ns, bogus_data,                      \
                           pin_miso, pin_mosi, pin_clk, pin_cs)           \
 	do {                                                             \
 		bi_decl(bi_4pins_with_names(pin_miso, name" SPI MISO",   \
@@ -75,12 +84,15 @@ LO_IMPLEMENTATION_H(spi, struct rp2040_hwspi, rp2040_hwspi)
 		                            pin_mosi, name" SPI CS"));   \
 		_rp2040_hwspi_init(self,                                 \
 		                   inst_num, mode, baudrate_hz,          \
+		                   min_delay_ns, bogus_data,             \
 		                   pin_miso, pin_mosi, pin_clk, pin_cs); \
 	} while(0)
 void _rp2040_hwspi_init(struct rp2040_hwspi *self,
                         enum rp2040_hwspi_instance inst_num,
                         enum spi_mode mode,
                         uint baudrate_hz,
+                        uint64_t min_delay_ns,
+                        uint8_t bogus_data,
                         uint pin_miso,
                         uint pin_mosi,
                         uint pin_clk,