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Date: Thu, 31 May 2018 00:42:11 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Eddie James <eajames@...ux.vnet.ibm.com>
Cc: linux-i2c <linux-i2c@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
devicetree <devicetree@...r.kernel.org>,
Wolfram Sang <wsa@...-dreams.de>,
Rob Herring <robh+dt@...nel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Joel Stanley <joel@....id.au>,
Mark Rutland <mark.rutland@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v8 4/7] i2c: fsi: Add abort and hardware reset procedures
On Thu, May 31, 2018 at 12:07 AM, Eddie James
<eajames@...ux.vnet.ibm.com> wrote:
> Add abort procedure for failed transfers. Add engine and bus reset
> procedures to recover from as many faults as possible.
>
Few small comments, after addressing which
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> Signed-off-by: Eddie James <eajames@...ux.vnet.ibm.com>
> ---
> drivers/i2c/busses/i2c-fsi.c | 179 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 179 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
> index be8e15c..e5dd0f7 100644
> --- a/drivers/i2c/busses/i2c-fsi.c
> +++ b/drivers/i2c/busses/i2c-fsi.c
> @@ -12,10 +12,12 @@
>
> #include <linux/bitfield.h>
> #include <linux/bitops.h>
> +#include <linux/delay.h>
> #include <linux/device.h>
> #include <linux/errno.h>
> #include <linux/fsi.h>
> #include <linux/i2c.h>
> +#include <linux/jiffies.h>
> #include <linux/kernel.h>
> #include <linux/list.h>
> #include <linux/module.h>
> @@ -122,6 +124,20 @@
> #define I2C_ESTAT_SELF_BUSY BIT(6)
> #define I2C_ESTAT_VERSION GENMASK(4, 0)
>
> +/* port busy register */
> +#define I2C_PORT_BUSY_RESET BIT(31)
> +
> +/* wait for command complete or data request */
> +#define I2C_CMD_SLEEP_MAX_US 500
> +#define I2C_CMD_SLEEP_MIN_US 50
> +
> +/* wait after reset; choose time from legacy driver */
> +#define I2C_RESET_SLEEP_MAX_US 2000
> +#define I2C_RESET_SLEEP_MIN_US 1000
> +
> +/* choose timeout length from legacy driver; it's well tested */
> +#define I2C_ABORT_TIMEOUT msecs_to_jiffies(100)
> +
> struct fsi_i2c_master {
> struct fsi_device *fsi;
> u8 fifo_size;
> @@ -208,6 +224,169 @@ static int fsi_i2c_set_port(struct fsi_i2c_port *port)
> return fsi_i2c_write_reg(fsi, I2C_FSI_RESET_ERR, &dummy);
> }
>
> +static int fsi_i2c_reset_bus(struct fsi_i2c_master *i2c)
> +{
> + int i, rc;
> + u32 mode, stat, ext, dummy = 0;
> +
> + rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_MODE, &mode);
> + if (rc)
> + return rc;
> +
> + mode |= I2C_MODE_DIAG;
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_MODE, &mode);
> + if (rc)
> + return rc;
> +
> + for (i = 0; i < 9; ++i) {
i++
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_SCL, &dummy);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_SET_SCL, &dummy);
> + if (rc)
> + return rc;
> + }
> +
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_SCL, &dummy);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_SDA, &dummy);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_SET_SCL, &dummy);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_SET_SDA, &dummy);
> + if (rc)
> + return rc;
> +
> + mode &= ~I2C_MODE_DIAG;
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_MODE, &mode);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_STAT, &stat);
> + if (rc)
> + return rc;
> +
> + /* check for hardware fault */
> + if (!(stat & I2C_STAT_SCL_IN) || !(stat & I2C_STAT_SDA_IN)) {
> + rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_ESTAT, &ext);
> + if (rc)
> + return rc;
> +
> + dev_err(&i2c->fsi->dev, "bus stuck status[%08X] ext[%08X]\n",
> + stat, ext);
> + }
> +
> + return 0;
> +}
> +
> +static int fsi_i2c_reset(struct fsi_i2c_master *i2c, u16 port)
> +{
> + int rc;
> + u32 mode, stat, dummy = 0;
> +
> + /* reset engine */
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_I2C, &dummy);
> + if (rc)
> + return rc;
> +
> + /* re-init engine */
> + rc = fsi_i2c_dev_init(i2c);
> + if (rc)
> + return rc;
> +
> + rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_MODE, &mode);
> + if (rc)
> + return rc;
> +
> + /* set port; default after reset is 0 */
> + if (port) {
> + mode = (mode & ~I2C_MODE_PORT) | FIELD_PREP(I2C_MODE_PORT,
> + port);
Hmm... This would look better as two expressions
mode &= ~..._PORT;
mode |= FIELD_PREP(...);
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_MODE, &mode);
> + if (rc)
> + return rc;
> + }
> +
> + /* reset busy register; hw workaround */
> + dummy = I2C_PORT_BUSY_RESET;
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_PORT_BUSY, &dummy);
> + if (rc)
> + return rc;
> +
> + /* force bus reset */
> + rc = fsi_i2c_reset_bus(i2c);
> + if (rc)
> + return rc;
> +
> + /* reset errors */
> + dummy = 0;
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_ERR, &dummy);
> + if (rc)
> + return rc;
> +
> + /* wait for command complete */
> + usleep_range(I2C_RESET_SLEEP_MIN_US, I2C_RESET_SLEEP_MAX_US);
> +
> + rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_STAT, &stat);
> + if (rc)
> + return rc;
> +
> + if (stat & I2C_STAT_CMD_COMP)
> + return rc;
> +
> + /* failed to get command complete; reset engine again */
> + rc = fsi_i2c_write_reg(i2c->fsi, I2C_FSI_RESET_I2C, &dummy);
> + if (rc)
> + return rc;
> +
> + /* re-init engine again */
> + return fsi_i2c_dev_init(i2c);
> +}
> +
> +static int fsi_i2c_abort(struct fsi_i2c_port *port, u32 status)
> +{
> + int rc;
> + unsigned long start;
> + u32 cmd = I2C_CMD_WITH_STOP;
> + struct fsi_device *fsi = port->master->fsi;
> +
> + rc = fsi_i2c_reset(port->master, port->port);
> + if (rc)
> + return rc;
> +
> + /* skip final stop command for these errors */
> + if (status & (I2C_STAT_PARITY | I2C_STAT_LOST_ARB | I2C_STAT_STOP_ERR))
> + return 0;
> +
> + /* write stop command */
> + rc = fsi_i2c_write_reg(fsi, I2C_FSI_CMD, &cmd);
> + if (rc)
> + return rc;
> +
> + /* wait until we see command complete in the master */
> + start = jiffies;
> +
> + do {
> + rc = fsi_i2c_read_reg(fsi, I2C_FSI_STAT, &status);
> + if (rc)
> + return rc;
> +
> + if (status & I2C_STAT_CMD_COMP)
> + return 0;
> +
> + usleep_range(I2C_CMD_SLEEP_MIN_US, I2C_CMD_SLEEP_MAX_US);
> + } while (time_after(start + I2C_ABORT_TIMEOUT, jiffies));
> +
> + return -ETIMEDOUT;
> +}
> +
> static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> int num)
> {
> --
> 1.8.3.1
>
--
With Best Regards,
Andy Shevchenko
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