zynq: spi: Honour the activation / deactivation delay

This is not currently implemented. Add support for this so that the
Chrome OS EC can be used reliably.

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>

diff --git a/drivers/spi/zynq_spi.c b/drivers/spi/zynq_spi.c
index 5a9b1f0..2b77f1c 100644 (file)
--- a/drivers/spi/zynq_spi.c
+++ b/drivers/spi/zynq_spi.c
@@ -56,6 +56,8 @@ struct zynq_spi_platdata {
        struct zynq_spi_regs *regs;
        u32 frequency;          /* input frequency */
        u32 speed_hz;
+       uint deactivate_delay_us;       /* Delay to wait after deactivate */
+       uint activate_delay_us;         /* Delay to wait after activate */
 };
 
 /* zynq spi priv */
@@ -63,6 +65,7 @@ struct zynq_spi_priv {
        struct zynq_spi_regs *regs;
        u8 cs;
        u8 mode;
+       ulong last_transaction_us;      /* Time of last transaction end */
        u8 fifo_depth;
        u32 freq;               /* required frequency */
 };
@@ -78,6 +81,10 @@ static int zynq_spi_ofdata_to_platdata(struct udevice *bus)
        /* FIXME: Use 250MHz as a suitable default */
        plat->frequency = fdtdec_get_int(blob, node, "spi-max-frequency",
                                        250000000);
+       plat->deactivate_delay_us = fdtdec_get_int(blob, node,
+                                       "spi-deactivate-delay", 0);
+       plat->activate_delay_us = fdtdec_get_int(blob, node,
+                                                "spi-activate-delay", 0);
        plat->speed_hz = plat->frequency / 2;
 
        debug("%s: regs=%p max-frequency=%d\n", __func__,
@@ -133,10 +140,19 @@ static int zynq_spi_probe(struct udevice *bus)
 static void spi_cs_activate(struct udevice *dev)
 {
        struct udevice *bus = dev->parent;
+       struct zynq_spi_platdata *plat = bus->platdata;
        struct zynq_spi_priv *priv = dev_get_priv(bus);
        struct zynq_spi_regs *regs = priv->regs;
        u32 cr;
 
+       /* If it's too soon to do another transaction, wait */
+       if (plat->deactivate_delay_us && priv->last_transaction_us) {
+               ulong delay_us;         /* The delay completed so far */
+               delay_us = timer_get_us() - priv->last_transaction_us;
+               if (delay_us < plat->deactivate_delay_us)
+                       udelay(plat->deactivate_delay_us - delay_us);
+       }
+
        clrbits_le32(&regs->cr, ZYNQ_SPI_CR_CS_MASK);
        cr = readl(&regs->cr);
        /*
@@ -147,15 +163,23 @@ static void spi_cs_activate(struct udevice *dev)
         */
        cr |= (~(1 << priv->cs) << ZYNQ_SPI_CR_SS_SHIFT) & ZYNQ_SPI_CR_CS_MASK;
        writel(cr, &regs->cr);
+
+       if (plat->activate_delay_us)
+               udelay(plat->activate_delay_us);
 }
 
 static void spi_cs_deactivate(struct udevice *dev)
 {
        struct udevice *bus = dev->parent;
+       struct zynq_spi_platdata *plat = bus->platdata;
        struct zynq_spi_priv *priv = dev_get_priv(bus);
        struct zynq_spi_regs *regs = priv->regs;
 
        setbits_le32(&regs->cr, ZYNQ_SPI_CR_CS_MASK);
+
+       /* Remember time of this transaction so we can honour the bus delay */
+       if (plat->deactivate_delay_us)
+               priv->last_transaction_us = timer_get_us();
 }
 
 static int zynq_spi_claim_bus(struct udevice *dev)