rockchip: spi: Set rxd sample delay when using high speed

At higher SPI bus speeds the SPI RX value is not available in time for
sampling at the normal time. Add a delay to ensure that we read the
correct data.

The value of 40ns is chosen arbitrarily. In my testing I can use a sample
delay of 1 even at 24MHz. But since it is not necessary, I have left that
case alone. It kicks in at 25MHz and up.

BUG=chrome-os-partner:56556
BRANCH=none
TEST=boot on gru and see no change at current speed

Change-Id: I3ef335d9a532eaef1e76034bd02e185acf11176a
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: e9b620c47fc3e39211487507fadb8657afdebee7
Original-Change-Id: I65d66d752cbbbee4d02f475de23a52069a0e9782
Original-Signed-off-by: Simon Glass <sjg@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/381311
Original-Commit-Ready: Julius Werner <jwerner@chromium.org>
Original-Tested-by: Simon Glass <sjg@google.com>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/16707
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

2 files changed, 17 insertions, 4 deletions

diff --git a/src/soc/rockchip/common/include/soc/spi.h b/src/soc/rockchip/common/include/soc/spi.h
index dcaa4711d2..0e1847c985 100644
--- a/src/soc/rockchip/common/include/soc/spi.h
+++ b/src/soc/rockchip/common/include/soc/spi.h
@@ -199,4 +199,7 @@ check_member(rockchip_spi, rxdr, 0x800);
 
 void rockchip_spi_init(unsigned int bus, unsigned int speed_hz);
 
+/* Set the receive sample delay in nanoseconds */
+void rockchip_spi_set_sample_delay(unsigned int bus, unsigned int delay_ns);
+
 #endif  /* ! __COREBOOT_SRC_SOC_ROCKCHIP_COMMON_INCLUDE_SOC_SPI_H */
diff --git a/src/soc/rockchip/common/spi.c b/src/soc/rockchip/common/spi.c
index f35f91589f..7dcaaadf19 100644
--- a/src/soc/rockchip/common/spi.c
+++ b/src/soc/rockchip/common/spi.c
@@ -32,7 +32,7 @@ struct rockchip_spi_slave {
 };
 
 #define SPI_TIMEOUT_US	1000
-#define SPI_SRCCLK_HZ   (99*MHz)
+#define SPI_SRCCLK_HZ   (198*MHz)
 #define SPI_FIFO_DEPTH	32
 
 static struct rockchip_spi_slave rockchip_spi_slaves[] = {
@@ -152,9 +152,6 @@ void rockchip_spi_init(unsigned int bus, unsigned int speed_hz)
 	/* Byte and Halfword Transform */
 	ctrlr0 |= (SPI_APB_8BIT << SPI_HALF_WORLD_TX_OFFSET);
 
-	/* Rxd Sample Delay */
-	ctrlr0 |= (0 << SPI_RXDSD_OFFSET);
-
 	/* Frame Format */
 	ctrlr0 |= (SPI_FRF_SPI << SPI_FRF_OFFSET);
 
@@ -165,6 +162,19 @@ void rockchip_spi_init(unsigned int bus, unsigned int speed_hz)
 	write32(&regs->rxftlr, SPI_FIFO_DEPTH / 2 - 1);
 }
 
+void rockchip_spi_set_sample_delay(unsigned int bus, unsigned int delay_ns)
+{
+	assert(bus >= 0 && bus < ARRAY_SIZE(rockchip_spi_slaves));
+	struct rockchip_spi *regs = rockchip_spi_slaves[bus].regs;
+	unsigned int rsd;
+
+	/* Rxd Sample Delay */
+	rsd = DIV_ROUND_CLOSEST(delay_ns * (SPI_SRCCLK_HZ >> 8), 1*GHz >> 8);
+	assert(rsd >= 0 && rsd <= 3);
+	clrsetbits_le32(&regs->ctrlr0, SPI_RXDSD_MASK << SPI_RXDSD_OFFSET,
+			rsd << SPI_RXDSD_OFFSET);
+}
+
 int spi_claim_bus(struct spi_slave *slave)
 {
 	spi_cs_activate(slave);