Hi James,
> -----Original Message-----
> From: James Hogan
> Sent: 29 July 2015 16:59
> To: Sifan Naeem; Wolfram Sang; linux-i2c@vger.kernel.org
> Subject: Re: [PATCH 7/7] i2c: img-scb: add handle for Master halt interrupt
>
> On 27/07/15 12:56, Sifan Naeem wrote:
> > Master halt is issued after each byte of a transaction is processed in
> > IP version 3.3.
> > Master halt will stall the bus by holding the SCK line low until the
> > halt bit in the scb_general_control is cleared.
> >
> > After the last byte of a transfer is processed we can use the Master
> > Halt interrupt to facilitate a repeated start transfer without issuing
> > a stop bit.
> >
> > Signed-off-by: Sifan Naeem <sifan.na...@imgtec.com>
> > ---
> > drivers/i2c/busses/i2c-img-scb.c | 25 +++++++++++++++++++++++++
> > 1 file changed, 25 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-img-scb.c
> > b/drivers/i2c/busses/i2c-img-scb.c
> > index 90faf48..df3d25a 100644
> > --- a/drivers/i2c/busses/i2c-img-scb.c
> > +++ b/drivers/i2c/busses/i2c-img-scb.c
> > @@ -151,6 +151,7 @@
> > #define INT_FIFO_EMPTYING BIT(12)
> > #define INT_TRANSACTION_DONE BIT(15)
> > #define INT_SLAVE_EVENT BIT(16)
> > +#define INT_MASTER_HALTED BIT(17)
> > #define INT_TIMING BIT(18)
> > #define INT_STOP_DETECTED BIT(19)
> >
> > @@ -177,6 +178,7 @@
> > INT_FIFO_FULL | \
> > INT_FIFO_FILLING | \
> > INT_FIFO_EMPTY | \
> > + INT_MASTER_HALTED | \
> > INT_STOP_DETECTED)
> >
> > #define INT_ENABLE_MASK_WAITSTOP (INT_SLAVE_EVENT | \
> > @@ -901,6 +903,17 @@ static unsigned int img_i2c_auto(struct img_i2c
> *i2c,
> > mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));
> >
> > if (i2c->msg.flags & I2C_M_RD) {
> > + if (int_status & INT_MASTER_HALTED) {
> > + img_i2c_read_fifo(i2c);
> > + if (i2c->msg.len == 0)
> > + return ISR_COMPLETE(0);
>
> don't you still need to wait for stop bit on last message?
>
> I suspect you could have a bit less duplication with something like this
> (again
> untested):
>
> diff --git a/drivers/i2c/busses/i2c-img-scb.c b/drivers/i2c/busses/i2c-img-
> scb.c
> index f694b47dcf74..2de2d63083e5 100644
> --- a/drivers/i2c/busses/i2c-img-scb.c
> +++ b/drivers/i2c/busses/i2c-img-scb.c
> @@ -875,13 +875,14 @@ static unsigned int img_i2c_auto(struct img_i2c *i2c,
> }
>
> if (i2c->msg.flags & I2C_M_RD) {
> - if (int_status & INT_FIFO_FULL_FILLING) {
> + if (int_status & (INT_FIFO_FULL_FILLING |
> INT_MASTER_HALTED)) {
> img_i2c_read_fifo(i2c);
> if (i2c->msg.len == 0)
> return ISR_WAITSTOP;
> }
> } else {
> - if (int_status & INT_FIFO_EMPTY_EMPTYING) {
> + if (int_status & (INT_FIFO_EMPTY_EMPTYING |
> + INT_MASTER_HALTED)) {
> /*
> * The write fifo empty indicates that we're in the
> * last byte so it's safe to start a new write @@ -895,6
> +896,14 @@ static unsigned int img_i2c_auto(struct img_i2c *i2c,
> img_i2c_write_fifo(i2c);
> }
> }
> + if (int_status & INT_MASTER_HALTED) {
> + /*
> + * Release and then enable transaction halt, to allow only a
> + * single byte to proceed.
> + */
> + img_i2c_transaction_halt(i2c, false);
> + img_i2c_transaction_halt(i2c, !i2c->last_msg);
> + }
>
> return 0;
> }
>
> would that do the trick?
>
Yes, I'll try this. Getting rid of patches 3/7 and 4/7 makes it easier to
squash these together.
Sifan
> Cheers
> James
>
> > + /*
> > + * Release and then enable transaction halt, to
> > + * allow only a single byte to proceed.
> > + */
> > + img_i2c_transaction_halt(i2c, false);
> > + img_i2c_transaction_halt(i2c, !i2c->last_msg);
> > + }
> > if (int_status & INT_FIFO_FULL_FILLING) {
> > img_i2c_read_fifo(i2c);
> > if (i2c->msg.len == 0) {
> > @@ -922,6 +935,18 @@ static unsigned int img_i2c_auto(struct img_i2c
> *i2c,
> > return ISR_COMPLETE(ret);
> > }
> > } else {
> > + if (int_status & INT_MASTER_HALTED) {
> > + if ((int_status & INT_FIFO_EMPTY) &&
> > + i2c->msg.len == 0)
> > + return ISR_COMPLETE(0);
> > + img_i2c_write_fifo(i2c);
> > + /*
> > + * Release and then enable transaction halt, to
> > + * allow only a single byte to proceed.
> > + */
> > + img_i2c_transaction_halt(i2c, false);
> > + img_i2c_transaction_halt(i2c, !i2c->last_msg);
> > + }
> > if (int_status & INT_FIFO_EMPTY) {
> > if (i2c->msg.len == 0) {
> > if (i2c->last_msg)
> >
--
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