[PATCH 2/4] i2c: uniphier-f: fill TX-FIFO only in IRQ handler for repeated START

Masahiro Yamada
2018-12-06T03:56:57Z

- For a repeated START condition, this controller starts data transfer
immediately after the slave address is written to the TX-FIFO.

- Once the TX-FIFO empty interrupt is asserted, the controller makes
a pause even if additional data are written to the TX-FIFO.

Given those circumstances, the data after a repeated START may not be
transferred if the interrupt is asserted while the TX-FIFO is being
filled up. A more reliable way is to append TX data only in the
interrupt handler.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

drivers/i2c/busses/i2c-uniphier-f.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-uniphier-f.c b/drivers/i2c/busses/i2c-uniphier-f.c
index fad2b00..d8a5db14 100644
--- a/drivers/i2c/busses/i2c-uniphier-f.c
+++ b/drivers/i2c/busses/i2c-uniphier-f.c
@@ -269,7 +269,8 @@ static irqreturn_t uniphier_fi2c_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}

-static void uniphier_fi2c_tx_init(struct uniphier_fi2c_priv *priv, u16 addr)
+static void uniphier_fi2c_tx_init(struct uniphier_fi2c_priv *priv, u16 addr,
+ bool repeat)
{
priv->enabled_irqs |= UNIPHIER_FI2C_INT_TE;
uniphier_fi2c_set_irqs(priv);
@@ -279,8 +280,12 @@ static void uniphier_fi2c_tx_init(struct uniphier_fi2c_priv *priv, u16 addr)
/* set slave address */
writel(UNIPHIER_FI2C_DTTX_CMD | addr << 1,
priv->membase + UNIPHIER_FI2C_DTTX);
- /* first chunk of data */
- uniphier_fi2c_fill_txfifo(priv, true);
+ /*
+ * First chunk of data. For a repeated START condition, do not write
+ * data to the TX fifo here to avoid the timing issue.
+ */
+ if (!repeat)
+ uniphier_fi2c_fill_txfifo(priv, true);
}

static void uniphier_fi2c_rx_init(struct uniphier_fi2c_priv *priv, u16 addr)
@@ -361,7 +366,7 @@ static int uniphier_fi2c_master_xfer_one(struct i2c_adapter *adap,
if (is_read)
uniphier_fi2c_rx_init(priv, msg->addr);
else
- uniphier_fi2c_tx_init(priv, msg->addr);
+ uniphier_fi2c_tx_init(priv, msg->addr, repeat);

dev_dbg(&adap->dev, "start condition\n");
/*
--
2.7.4