[v2,0/2] i2c: rcar: improve Gen3 support

Here is a series paving the way for Gen4 support. This time we properly
apply the Gen3 specific features. See the patch comments for further
information and changelogs. This has been tested on a Renesas Falcon
board with a R-Car V3U SoC at various bus speeds. Because the
calculation formulas are crucial, testing on board farms would be much
appreciated!

Thanks and happy hacking!


Wolfram Sang (2):
  i2c: rcar: reset controller is mandatory for Gen3+
  i2c: rcar: improve accuracy for R-Car Gen3+

 drivers/i2c/busses/i2c-rcar.c | 150 ++++++++++++++++++++++------------
 1 file changed, 100 insertions(+), 50 deletions(-)

Hi Wolfram,

On Tue, Sep 19, 2023 at 5:23 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> Initially, we only needed a reset controller to make sure RXDMA works at
> least once per transfer. Meanwhile, documentation has been updated. It
> now says that a reset has to be performed prior every transaction, even
> if it is non-DMA. So, make the reset controller a requirement instead of
> being optional. And bail out if resetting fails.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
>
> Change since v1:
> * bail out when resetting fails (Thanks, Geert!)

Thanks for the update!

> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -838,12 +838,10 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
>
>         /* Gen3 needs a reset before allowing RXDMA once */
>         if (priv->devtype == I2C_RCAR_GEN3) {
> -               priv->flags |= ID_P_NO_RXDMA;
> -               if (!IS_ERR(priv->rstc)) {
> -                       ret = rcar_i2c_do_reset(priv);
> -                       if (ret == 0)
> -                               priv->flags &= ~ID_P_NO_RXDMA;
> -               }
> +               priv->flags &= ~ID_P_NO_RXDMA;
> +               ret = rcar_i2c_do_reset(priv);
> +               if (ret)
> +                       return ret;

goto out

>         }
>
>         rcar_i2c_init(priv);
> @@ -1096,11 +1094,13 @@ static int rcar_i2c_probe(struct platform_device *pdev)
>
>         if (priv->devtype == I2C_RCAR_GEN3) {
>                 priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
> -               if (!IS_ERR(priv->rstc)) {
> -                       ret = reset_control_status(priv->rstc);
> -                       if (ret < 0)
> -                               priv->rstc = ERR_PTR(-ENOTSUPP);
> -               }
> +               if (IS_ERR(priv->rstc))
> +                       return dev_err_probe(&pdev->dev, PTR_ERR(priv->rstc),
> +                                            "couldn't get reset");

pm_runtime_put(dev);
goto out_pm_disable;

Sorry for not noticing before.
(I'm sooo happy you didn't retain my Rb-tag ;-)

> +
> +               ret = reset_control_status(priv->rstc);
> +               if (ret < 0)
> +                       return ret;

Likewise

>         }
>
>         /* Stay always active when multi-master to keep arbitration working */

Gr{oetje,eeting}s,

                        Geert