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Message-ID: <20200910030225.GA10495@mani>
Date: Thu, 10 Sep 2020 08:32:25 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...il.com>
Cc: Andreas Färber <afaerber@...e.de>,
linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-actions@...ts.infradead.org
Subject: Re: [PATCH v2 1/1] i2c: busses: Add support for atomic transfers in
Actions Semi Owl driver
On 0909, Cristian Ciocaltea wrote:
> Hi Mani,
>
> Thanks for the review!
>
> On Wed, Sep 09, 2020 at 08:47:48PM +0530, Manivannan Sadhasivam wrote:
> > Hi Cristi,
> >
> > On 0908, Cristian Ciocaltea wrote:
> > > Atomic transfers are required to properly power off a machine through
> > > an I2C controlled PMIC, such as the Actions Semi ATC260x series.
> > >
> > > System shutdown may happen with interrupts being disabled and, as a
> > > consequence, the kernel may hang if the driver does not support atomic
> > > transfers.
> > >
> > > This functionality is essentially implemented by polling the FIFO
> > > Status register until either Command Execute Completed or NACK Error
> > > bits are set.
> > >
> >
> > Thanks for the patch! I just have couple of minor comments and other
> > than that it looks good to me.
> >
> > > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...il.com>
> > > ---
> > > Changes in v2:
> > > - Dropped unused return codes from owl_i2c_xfer_data(), per Mani's review
> > > - Rebased patch on v5.9-rc4
> > >
> > > drivers/i2c/busses/i2c-owl.c | 78 ++++++++++++++++++++++++++----------
> > > 1 file changed, 57 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-owl.c b/drivers/i2c/busses/i2c-owl.c
> > > index 672f1f239bd6..29605257831f 100644
> > > --- a/drivers/i2c/busses/i2c-owl.c
> > > +++ b/drivers/i2c/busses/i2c-owl.c
> > > @@ -14,6 +14,7 @@
> > > #include <linux/i2c.h>
> > > #include <linux/interrupt.h>
> > > #include <linux/io.h>
> > > +#include <linux/iopoll.h>
> > > #include <linux/module.h>
> > > #include <linux/of_device.h>
> > >
> > > @@ -76,6 +77,7 @@
> > > #define OWL_I2C_FIFOCTL_TFR BIT(2)
> > >
> > > /* I2Cc_FIFOSTAT Bit Mask */
> > > +#define OWL_I2C_FIFOSTAT_CECB BIT(0)
> > > #define OWL_I2C_FIFOSTAT_RNB BIT(1)
> > > #define OWL_I2C_FIFOSTAT_RFE BIT(2)
> > > #define OWL_I2C_FIFOSTAT_TFF BIT(5)
> > > @@ -83,7 +85,8 @@
> > > #define OWL_I2C_FIFOSTAT_RFD GENMASK(15, 8)
> > >
> > > /* I2C bus timeout */
> > > -#define OWL_I2C_TIMEOUT msecs_to_jiffies(4 * 1000)
> > > +#define OWL_I2C_TIMEOUT_MS (4 * 1000)
> > > +#define OWL_I2C_TIMEOUT msecs_to_jiffies(OWL_I2C_TIMEOUT_MS)
> > >
> > > #define OWL_I2C_MAX_RETRIES 50
> > >
> > > @@ -161,29 +164,25 @@ static void owl_i2c_set_freq(struct owl_i2c_dev *i2c_dev)
> > > writel(OWL_I2C_DIV_FACTOR(val), i2c_dev->base + OWL_I2C_REG_CLKDIV);
> > > }
> > >
> > > -static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
> > > +static void owl_i2c_xfer_data(struct owl_i2c_dev *i2c_dev)
> > > {
> > > - struct owl_i2c_dev *i2c_dev = _dev;
> > > struct i2c_msg *msg = i2c_dev->msg;
> > > - unsigned long flags;
> > > unsigned int stat, fifostat;
> > >
> > > - spin_lock_irqsave(&i2c_dev->lock, flags);
> > > -
> > > i2c_dev->err = 0;
> > >
> > > /* Handle NACK from slave */
> > > fifostat = readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT);
> > > if (fifostat & OWL_I2C_FIFOSTAT_RNB) {
> > > i2c_dev->err = -ENXIO;
> > > - goto stop;
> > > + return;
> > > }
> > >
> > > /* Handle bus error */
> > > stat = readl(i2c_dev->base + OWL_I2C_REG_STAT);
> > > if (stat & OWL_I2C_STAT_BEB) {
> > > i2c_dev->err = -EIO;
> > > - goto stop;
> > > + return;
> > > }
> > >
> > > /* Handle FIFO read */
> > > @@ -196,18 +195,28 @@ static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
> > > } else {
> > > /* Handle the remaining bytes which were not sent */
> > > while (!(readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
> > > - OWL_I2C_FIFOSTAT_TFF) && i2c_dev->msg_ptr < msg->len) {
> > > + OWL_I2C_FIFOSTAT_TFF) && i2c_dev->msg_ptr < msg->len) {
> >
> > Spurious change?
>
> I have just fixed a small indentation issue (removed extra space char
> in front of OWL_I2C...). I will revert it if you think it's not the right
> context for doing this (located ~10 lines bellow the previous edit).
>
The extra space was there to align with the starting of 'readl', so please keep
it as it is.
> > > writel(msg->buf[i2c_dev->msg_ptr++],
> > > i2c_dev->base + OWL_I2C_REG_TXDAT);
> > > }
> > > }
> > > +}
> > > +
> > > +static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
> > > +{
> > > + struct owl_i2c_dev *i2c_dev = _dev;
> > > + unsigned long flags;
> > > +
> > > + spin_lock_irqsave(&i2c_dev->lock, flags);
> > > +
> > > + owl_i2c_xfer_data(i2c_dev);
> > >
> > > -stop:
> > > /* Clear pending interrupts */
> > > owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_STAT,
> > > OWL_I2C_STAT_IRQP, true);
> > >
> > > complete_all(&i2c_dev->msg_complete);
> > > +
> > > spin_unlock_irqrestore(&i2c_dev->lock, flags);
> > >
> > > return IRQ_HANDLED;
> > > @@ -235,8 +244,8 @@ static int owl_i2c_check_bus_busy(struct i2c_adapter *adap)
> > > return 0;
> > > }
> > >
> > > -static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > > - int num)
> > > +static int owl_i2c_xfer_common(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > > + int num, bool atomic)
> > > {
> > > struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> > > struct i2c_msg *msg;
> > > @@ -280,11 +289,12 @@ static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > > goto err_exit;
> > > }
> > >
> > > - reinit_completion(&i2c_dev->msg_complete);
> > > + if (!atomic)
> > > + reinit_completion(&i2c_dev->msg_complete);
> > >
> > > - /* Enable I2C controller interrupt */
> > > + /* Enable/disable I2C controller interrupt */
> > > owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> > > - OWL_I2C_CTL_IRQE, true);
> > > + OWL_I2C_CTL_IRQE, !atomic);
> > >
> > > /*
> > > * Select: FIFO enable, Master mode, Stop enable, Data count enable,
> > > @@ -352,20 +362,33 @@ static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > >
> > > spin_unlock_irqrestore(&i2c_dev->lock, flags);
> > >
> > > - time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> > > - adap->timeout);
> > > + if (atomic) {
> > > + /* Wait for Command Execute Completed or NACK Error bits */
> > > + ret = readl_poll_timeout_atomic(i2c_dev->base + OWL_I2C_REG_FIFOSTAT,
> > > + val, val & (OWL_I2C_FIFOSTAT_CECB |
> > > + OWL_I2C_FIFOSTAT_RNB),
> > > + 10, OWL_I2C_TIMEOUT_MS * 1000);
> > > + } else {
> > > + time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> > > + adap->timeout);
> > > + if (!time_left)
> > > + ret = -ETIMEDOUT;
> > > + }
> > >
> > > spin_lock_irqsave(&i2c_dev->lock, flags);
> > > - if (time_left == 0) {
> > > +
> > > + if (ret) {
> > > dev_err(&adap->dev, "Transaction timed out\n");
> > > /* Send stop condition and release the bus */
> > > owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> > > OWL_I2C_CTL_GBCC_STOP | OWL_I2C_CTL_RB,
> > > true);
> > > - ret = -ETIMEDOUT;
> > > goto err_exit;
> > > }
> > >
> > > + if (atomic)
> > > + owl_i2c_xfer_data(i2c_dev);
> >
> > You are not clearing the pending interrupts here.
>
> I assumed this is not needed for atomic contexts since the controller
> interrupt is disabled (please see the comment above: Enable/disable I2C
> controller interrupt).
>
> Otherwise I will simply move the clear pending interrupts code from
> owl_i2c_interrupt() to owl_i2c_xfer_data().
>
Hmm. My intention was to say that we are not clearing the error bits when they
happen but I misinterpreted that setting IRQP will take care of that but it
doesn't.
So I think you should submit a patch which writes to RNB and BEB fields when
they are set (writing 1 will clear the interrupts) and ignore my previous
comment.
Thanks,
Mani
> > Thanks,
> > Mani
> >
> > > +
> > > ret = i2c_dev->err < 0 ? i2c_dev->err : num;
> > >
> > > err_exit:
> > > @@ -379,9 +402,22 @@ static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > > return ret;
> > > }
> > >
> > > +static int owl_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > > + int num)
> > > +{
> > > + return owl_i2c_xfer_common(adap, msgs, num, false);
> > > +}
> > > +
> > > +static int owl_i2c_xfer_atomic(struct i2c_adapter *adap,
> > > + struct i2c_msg *msgs, int num)
> > > +{
> > > + return owl_i2c_xfer_common(adap, msgs, num, true);
> > > +}
> > > +
> > > static const struct i2c_algorithm owl_i2c_algorithm = {
> > > - .master_xfer = owl_i2c_master_xfer,
> > > - .functionality = owl_i2c_func,
> > > + .master_xfer = owl_i2c_xfer,
> > > + .master_xfer_atomic = owl_i2c_xfer_atomic,
> > > + .functionality = owl_i2c_func,
> > > };
> > >
> > > static const struct i2c_adapter_quirks owl_i2c_quirks = {
> > > --
> > > 2.28.0
> > >
>
> Kind regards,
> Cristi
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