i2c: mpc: Correct I2C reset procedure

[ Upstream commit ebe82cf92cd4825c3029434cabfcd2f1780e64be ]

Current I2C reset procedure is broken in two ways:
1) It only generate 1 START instead of 9 STARTs and STOP.
2) It leaves the bus Busy so every I2C xfer after the first
   fixup calls the reset routine again, for every xfer there after.

This fixes both errors.

Signed-off-by: Joakim Tjernlund <joakim.tjernlund@infinera.com>
Acked-by: Scott Wood <oss@buserror.net>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 90e4f839eb1cbc9a8c90f62a8680763d22f86171..d153fc28e6bfb457fffac34af7d25e0e4dc2f9eb 100644 (file)
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -107,23 +107,30 @@ static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
 /* Sometimes 9th clock pulse isn't generated, and slave doesn't release
  * the bus, because it wants to send ACK.
  * Following sequence of enabling/disabling and sending start/stop generates
- * the 9 pulses, so it's all OK.
+ * the 9 pulses, each with a START then ending with STOP, so it's all OK.
  */
 static void mpc_i2c_fixup(struct mpc_i2c *i2c)
 {
        int k;
-       u32 delay_val = 1000000 / i2c->real_clk + 1;
-
-       if (delay_val < 2)
-               delay_val = 2;
+       unsigned long flags;
 
        for (k = 9; k; k--) {
                writeccr(i2c, 0);
-               writeccr(i2c, CCR_MSTA | CCR_MTX | CCR_MEN);
+               writeb(0, i2c->base + MPC_I2C_SR); /* clear any status bits */
+               writeccr(i2c, CCR_MEN | CCR_MSTA); /* START */
+               readb(i2c->base + MPC_I2C_DR); /* init xfer */
+               udelay(15); /* let it hit the bus */
+               local_irq_save(flags); /* should not be delayed further */
+               writeccr(i2c, CCR_MEN | CCR_MSTA | CCR_RSTA); /* delay SDA */
                readb(i2c->base + MPC_I2C_DR);
-               writeccr(i2c, CCR_MEN);
-               udelay(delay_val << 1);
+               if (k != 1)
+                       udelay(5);
+               local_irq_restore(flags);
        }
+       writeccr(i2c, CCR_MEN); /* Initiate STOP */
+       readb(i2c->base + MPC_I2C_DR);
+       udelay(15); /* Let STOP propagate */
+       writeccr(i2c, 0);
 }
 
 static int i2c_wait(struct mpc_i2c *i2c, unsigned timeout, int writing)