Merge branch 'lukeshu/dma'

1 files changed, 57 insertions, 18 deletions

diff --git a/libhw/rp2040_include/libhw/rp2040_hwspi.h b/libhw/rp2040_include/libhw/rp2040_hwspi.h
index 76e0709..eb54cdc 100644
--- a/libhw/rp2040_include/libhw/rp2040_hwspi.h
+++ b/libhw/rp2040_include/libhw/rp2040_hwspi.h
@@ -9,6 +9,7 @@
 
 #include <pico/binary_info.h> /* for bi_* */
 
+#include <libcr_ipc/sema.h>
 #include <libmisc/private.h>
 
 #include <libhw/generic/spi.h>
@@ -20,9 +21,19 @@ 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            dma_tx_data;
+	uint            dma_tx_ctrl;
+	uint            dma_rx_data;
+	uint            dma_rx_ctrl;
 
-	uint    pin_cs;
+	/* mutable */
+	uint64_t        dead_until_ns;
+	cr_sema_t       sema;
 	END_PRIVATE(LIBHW_RP2040_HWSPI_H)
 };
 LO_IMPLEMENTATION_H(io_duplex_readwriter, struct rp2040_hwspi, rp2040_hwspi)
@@ -31,14 +42,18 @@ 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
+ * @param dma{1-4}    : uint                       : DMA channel; any unused channel
  *
  * There is no bit-order argument; the RP2040's hardware SPI always
  * uses MSB-first bit order.
@@ -48,16 +63,32 @@ LO_IMPLEMENTATION_H(spi, struct rp2040_hwspi, rp2040_hwspi)
  * the CPU.  This is because the PL022 has a maximum of 16-bit frames,
  * but we need to be able to do *at least* 32-bit frames (and ideally,
  * much larger).  By managing it ourselves, we can just keep CS pulled
- * low extra-long, making the frame extra-long.  However, this means
- * that we can't SPI so fast that the CPU can't do things in time;
- * experimentally much faster than 60MHz seems to be when I start
- * getting mangled messages.  We wouldn't have this speed limit with a
- * PIO-based SPI driver, because it could toggle CLK and CS in
- * lock-step with receiving data from the FIFO.
+ * low extra-long, making the frame extra-long.
+ *
+ * Restrictions on baudrate:
+ *
+ * - The PL022 requires that the baudrate is an even-number fraction
+ *   of clk_peri.
+ *    + This implies that the maximum baudrate is clk_peri/2.
+ *    + Pico-SDK' default clk_peri is 125MHz, max is 200MHz.
+ * - The CS-from-GPIO hack above means that that we can't go so fast
+ *   that the CPU can't do things in time.
+ *    + Experimentally:
+ *      | clk_sys=125MHz | baud=31.25MHz | works OK                         |
+ *      | clk_sys=160MHz | baud=40   MHz | works OK                         |
+ *      | clk_sys=170MHz | baud=42.5 MHz | works OK                         |
+ *      | clk_sys=180MHz | baud=45   MHz | mangled in funny ways?           |
+ *      | clk_sys=200MHz | baud=50   MHz | messages get shifted right a bit |
+ *      | clk_sys=125MHz | baud=62.5 MHz | messages get shifted right a bit |
+ *
+ * Both of these restrictions aught to be avoidable by using a
+ * PIO-based SPI driver instead of this PLL02-based driver.
  */
 #define rp2040_hwspi_init(self, name,                                    \
                           inst_num, mode, baudrate_hz,                   \
-                          pin_miso, pin_mosi, pin_clk, pin_cs)           \
+                          min_delay_ns, bogus_data,                      \
+                          pin_miso, pin_mosi, pin_clk, pin_cs,           \
+                          dma1, dma2, dma3, dma4)                        \
 	do {                                                             \
 		bi_decl(bi_4pins_with_names(pin_miso, name" SPI MISO",   \
 		                            pin_mosi, name" SPI MOSI",   \
@@ -65,15 +96,23 @@ LO_IMPLEMENTATION_H(spi, struct rp2040_hwspi, rp2040_hwspi)
 		                            pin_mosi, name" SPI CS"));   \
 		_rp2040_hwspi_init(self,                                 \
 		                   inst_num, mode, baudrate_hz,          \
-		                   pin_miso, pin_mosi, pin_clk, pin_cs); \
+		                   min_delay_ns, bogus_data,             \
+		                   pin_miso, pin_mosi, pin_clk, pin_cs,  \
+		                   dma1, dma2, dma3, dma4);              \
 	} 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,
-                        uint pin_cs);
+                        uint pin_cs,
+                        uint dma1,
+                        uint dma2,
+                        uint dma3,
+                        uint dma4);
 
 #endif /* _LIBHW_RP2040_HWSPI_H_ */