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Date: Wed, 8 Jan 2020 14:03:48 +0100
From: Neil Armstrong <narmstrong@...libre.com>
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
linux-i2c@...r.kernel.org, linux-amlogic@...ts.infradead.org,
wsa@...-dreams.de
Cc: khilman@...libre.com, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, b.galvani@...il.com,
jian.hu@...ogic.com
Subject: Re: [PATCH] i2c: meson: implement the master_xfer_atomic callback
On 08/01/2020 00:29, Martin Blumenstingl wrote:
> Boards with some of the 32-bit SoCs (mostly Meson8 and Meson8m2) use a
> Ricoh RN5T618 PMU which acts as system power controller. The driver for
> the system power controller may need to the I2C bus just before shutting
> down or rebooting the system. At this stage the interrupts may be
> disabled already.
>
> Implement the master_xfer_atomic callback so the driver for the RN5T618
> PMU can communicate properly with the PMU when shutting down or
> rebooting the board. The CTRL register has a status bit which can be
> polled to determine when processing has completed. According to the
> public S805 datasheet the value 0 means "idle" and 1 means "running".
>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
> drivers/i2c/busses/i2c-meson.c | 97 +++++++++++++++++++++++-----------
> 1 file changed, 65 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
> index 1e2647f9a2a7..7486b46e475f 100644
> --- a/drivers/i2c/busses/i2c-meson.c
> +++ b/drivers/i2c/busses/i2c-meson.c
> @@ -10,6 +10,7 @@
> #include <linux/i2c.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> +#include <linux/iopoll.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -213,6 +214,30 @@ static void meson_i2c_prepare_xfer(struct meson_i2c *i2c)
> writel(i2c->tokens[1], i2c->regs + REG_TOK_LIST1);
> }
>
> +static void meson_i2c_transfer_complete(struct meson_i2c *i2c, u32 ctrl)
> +{
> + if (ctrl & REG_CTRL_ERROR) {
> + /*
> + * The bit is set when the IGNORE_NAK bit is cleared
> + * and the device didn't respond. In this case, the
> + * I2C controller automatically generates a STOP
> + * condition.
> + */
> + dev_dbg(i2c->dev, "error bit set\n");
> + i2c->error = -ENXIO;
> + i2c->state = STATE_IDLE;
> + } else {
> + if (i2c->state == STATE_READ && i2c->count)
> + meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos,
> + i2c->count);
> +
> + i2c->pos += i2c->count;
> +
> + if (i2c->pos >= i2c->msg->len)
> + i2c->state = STATE_IDLE;
> + }
> +}
> +
> static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
> {
> struct meson_i2c *i2c = dev_id;
> @@ -232,27 +257,9 @@ static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
> return IRQ_NONE;
> }
>
> - if (ctrl & REG_CTRL_ERROR) {
> - /*
> - * The bit is set when the IGNORE_NAK bit is cleared
> - * and the device didn't respond. In this case, the
> - * I2C controller automatically generates a STOP
> - * condition.
> - */
> - dev_dbg(i2c->dev, "error bit set\n");
> - i2c->error = -ENXIO;
> - i2c->state = STATE_IDLE;
> - complete(&i2c->done);
> - goto out;
> - }
> -
> - if (i2c->state == STATE_READ && i2c->count)
> - meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos, i2c->count);
> + meson_i2c_transfer_complete(i2c, ctrl);
>
> - i2c->pos += i2c->count;
> -
> - if (i2c->pos >= i2c->msg->len) {
> - i2c->state = STATE_IDLE;
> + if (i2c->state == STATE_IDLE) {
> complete(&i2c->done);
> goto out;
> }
> @@ -279,10 +286,11 @@ static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
> }
>
> static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
> - int last)
> + int last, bool atomic)
> {
> unsigned long time_left, flags;
> int ret = 0;
> + u32 ctrl;
>
> i2c->msg = msg;
> i2c->last = last;
> @@ -300,13 +308,24 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
>
> i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
> meson_i2c_prepare_xfer(i2c);
> - reinit_completion(&i2c->done);
> +
> + if (!atomic)
> + reinit_completion(&i2c->done);
>
> /* Start the transfer */
> meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, REG_CTRL_START);
>
> - time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
> - time_left = wait_for_completion_timeout(&i2c->done, time_left);
> + if (atomic) {
> + ret = readl_poll_timeout_atomic(i2c->regs + REG_CTRL, ctrl,
> + !(ctrl & REG_CTRL_STATUS),
> + 10, I2C_TIMEOUT_MS * 1000);
> + } else {
> + time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
> + time_left = wait_for_completion_timeout(&i2c->done, time_left);
> +
> + if (!time_left)
> + ret = -ETIMEDOUT;
> + }
>
> /*
> * Protect access to i2c struct and registers from interrupt
> @@ -315,13 +334,14 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
> */
> spin_lock_irqsave(&i2c->lock, flags);
>
> + if (atomic && !ret)
> + meson_i2c_transfer_complete(i2c, ctrl);
> +
> /* Abort any active operation */
> meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
>
> - if (!time_left) {
> + if (ret)
> i2c->state = STATE_IDLE;
> - ret = -ETIMEDOUT;
> - }
>
> if (i2c->error)
> ret = i2c->error;
> @@ -331,8 +351,8 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
> return ret;
> }
>
> -static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> - int num)
> +static int meson_i2c_xfer_messages(struct i2c_adapter *adap,
> + struct i2c_msg *msgs, int num, bool atomic)
> {
> struct meson_i2c *i2c = adap->algo_data;
> int i, ret = 0;
> @@ -340,7 +360,7 @@ static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> clk_enable(i2c->clk);
>
> for (i = 0; i < num; i++) {
> - ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1);
> + ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1, atomic);
> if (ret)
> break;
> }
> @@ -350,14 +370,27 @@ static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> return ret ?: i;
> }
>
> +static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> + int num)
> +{
> + return meson_i2c_xfer_messages(adap, msgs, num, false);
> +}
> +
> +static int meson_i2c_xfer_atomic(struct i2c_adapter *adap,
> + struct i2c_msg *msgs, int num)
> +{
> + return meson_i2c_xfer_messages(adap, msgs, num, true);
> +}
> +
> static u32 meson_i2c_func(struct i2c_adapter *adap)
> {
> return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> }
>
> static const struct i2c_algorithm meson_i2c_algorithm = {
> - .master_xfer = meson_i2c_xfer,
> - .functionality = meson_i2c_func,
> + .master_xfer = meson_i2c_xfer,
> + .master_xfer_atomic = meson_i2c_xfer_atomic,
> + .functionality = meson_i2c_func,
> };
>
> static int meson_i2c_probe(struct platform_device *pdev)
>
Looks fine
Reviewed-by: Neil Armstrong <narmstrong@...libre.com>
Neil
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