[PATCH 3/3] i2c: mpc: implement erratum A-004447 workaround

[Andy Shevchenko]

On Thursday, May 6, 2021, Chris Packham <chris.packham at alliedtelesis.co.nz>
wrote:

> The P2040/P2041 has an erratum where the normal i2c recovery mechanism
> does not work. Implement the alternative recovery mechanism documented
> in the P2040 Chip Errata Rev Q.
>
> Signed-off-by: Chris Packham <chris.packham at alliedtelesis.co.nz>
> ---
>  drivers/i2c/busses/i2c-mpc.c | 88 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 86 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
> index 30d9e89a3db2..052e37718771 100644
> --- a/drivers/i2c/busses/i2c-mpc.c
> +++ b/drivers/i2c/busses/i2c-mpc.c
> @@ -45,6 +45,7 @@
>  #define CCR_MTX  0x10
>  #define CCR_TXAK 0x08
>  #define CCR_RSTA 0x04
> +#define CCR_RSVD 0x02
>
>  #define CSR_MCF  0x80
>  #define CSR_MAAS 0x40
> @@ -97,7 +98,7 @@ struct mpc_i2c {
>         u32 block;
>         int rc;
>         int expect_rxack;
> -
> +       bool has_errata_A004447;
>  };
>
>  struct mpc_i2c_divider {
> @@ -136,6 +137,83 @@ static void mpc_i2c_fixup(struct mpc_i2c *i2c)
>         }
>  }
>
> +static int i2c_mpc_wait_sr(struct mpc_i2c *i2c, int mask)
> +{
> +       unsigned long timeout = jiffies + usecs_to_jiffies(100);
> +       int ret = 0;
> +
> +       while ((readb(i2c->base + MPC_I2C_SR) & mask) == 0) {
> +               if (time_after(jiffies, timeout)) {
> +                       ret = -ETIMEDOUT;
> +                       break;
> +               }
> +               cond_resched();
> +       }
> +
> +       return ret;
> +}


readb_poll_timeout()


> +
> +/*
> + * Workaround for Erratum A004447. From the P2040CE Rev Q
> + *
> + * 1.  Set up the frequency divider and sampling rate.
> + * 2.  I2CCR - a0h
> + * 3.  Poll for I2CSR[MBB] to get set.
> + * 4.  If I2CSR[MAL] is set (an indication that SDA is stuck low), then
> go to
> + *     step 5. If MAL is not set, then go to step 13.
> + * 5.  I2CCR - 00h
> + * 6.  I2CCR - 22h
> + * 7.  I2CCR - a2h
> + * 8.  Poll for I2CSR[MBB] to get set.
> + * 9.  Issue read to I2CDR.
> + * 10. Poll for I2CSR[MIF] to be set.
> + * 11. I2CCR - 82h
> + * 12. Workaround complete. Skip the next steps.
> + * 13. Issue read to I2CDR.
> + * 14. Poll for I2CSR[MIF] to be set.
> + * 15. I2CCR - 80h
> + */
> +static void mpc_i2c_fixup_A004447(struct mpc_i2c *i2c)
> +{
> +       int ret;
> +       u32 val;
> +
> +       writeccr(i2c, CCR_MEN | CCR_MSTA);
> +       ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
> +       if (ret) {
> +               dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
> +               return;
> +       }
> +
> +       val = readb(i2c->base + MPC_I2C_SR);
> +
> +       if (val & CSR_MAL) {
> +               writeccr(i2c, 0x00);
> +               writeccr(i2c, CCR_MSTA | CCR_RSVD);
> +               writeccr(i2c, CCR_MEN | CCR_MSTA | CCR_RSVD);
> +               ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
> +               if (ret) {
> +                       dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
> +                       return;
> +               }
> +               val = readb(i2c->base + MPC_I2C_DR);
> +               ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
> +               if (ret) {
> +                       dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
> +                       return;
> +               }
> +               writeccr(i2c, CCR_MEN | CCR_RSVD);
> +       } else {
> +               val = readb(i2c->base + MPC_I2C_DR);
> +               ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
> +               if (ret) {
> +                       dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
> +                       return;
> +               }
> +               writeccr(i2c, CCR_MEN);
> +       }
> +}
> +
>  #if defined(CONFIG_PPC_MPC52xx) || defined(CONFIG_PPC_MPC512x)
>  static const struct mpc_i2c_divider mpc_i2c_dividers_52xx[] = {
>         {20, 0x20}, {22, 0x21}, {24, 0x22}, {26, 0x23},
> @@ -670,7 +748,10 @@ static int fsl_i2c_bus_recovery(struct i2c_adapter
> *adap)
>  {
>         struct mpc_i2c *i2c = i2c_get_adapdata(adap);
>
> -       mpc_i2c_fixup(i2c);
> +       if (i2c->has_errata_A004447)
> +               mpc_i2c_fixup_A004447(i2c);
> +       else
> +               mpc_i2c_fixup(i2c);
>
>         return 0;
>  }
> @@ -767,6 +848,9 @@ static int fsl_i2c_probe(struct platform_device *op)
>         }
>         dev_info(i2c->dev, "timeout %u us\n", mpc_ops.timeout * 1000000 /
> HZ);
>
> +       if (of_property_read_bool(op->dev.of_node,
> "fsl,i2c-erratum-a004447"))
> +               i2c->has_errata_A004447 = true;
> +
>         i2c->adap = mpc_ops;
>         scnprintf(i2c->adap.name, sizeof(i2c->adap.name),
>                   "MPC adapter (%s)", of_node_full_name(op->dev.of_node));
> --
> 2.31.1
>
>

-- 
With Best Regards,
Andy Shevchenko
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