Re: [PATCHv2] i2c-mpc: Correct I2C reset procedure

[Joakim Tjernlund <Joakim.Tjernlund@infinera.com>]

On Tue, 2017-05-16 at 17:13 +0200, Joakim Tjernlund wrote:
> On Thu, 2017-05-11 at 14:20 +0200, Joakim Tjernlund wrote:
> > 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.
> 
> Ping?

Ping again, pretty please?

> 
> > 
> > Signed-off-by: Joakim Tjernlund <joakim.tjernlund@infinera.com>
> > ---
> > 
> >  v2 -  Remove io barrier call.
> >  drivers/i2c/busses/i2c-mpc.c | 23 +++++++++++++++--------
> >  1 file changed, 15 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
> > index 8393140..6b5e6ce4 100644
> > --- a/drivers/i2c/busses/i2c-mpc.c
> > +++ b/drivers/i2c/busses/i2c-mpc.c
> > @@ -104,23 +104,30 @@ 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)