On 07.06.2019 06:45, Andrey Smirnov wrote:
> Transfer size of zero means a request to do an address-only
> transfer. Since the HW support this, we probably shouldn't be just
> ignoring such requests. While at it allow DP_AUX_I2C_MOT flag to pass
> through, since it is supported by the HW as well.
>
> Signed-off-by: Andrey Smirnov <andrew.smir...@gmail.com>
Reviewed-by: Andrzej Hajda <a.ha...@samsung.com>

 --
Regards
Andrzej
> Cc: Andrzej Hajda <a.ha...@samsung.com>
> Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Cc: Tomi Valkeinen <tomi.valkei...@ti.com>
> Cc: Andrey Gusakov <andrey.gusa...@cogentembedded.com>
> Cc: Philipp Zabel <p.za...@pengutronix.de>
> Cc: Cory Tusar <cory.tu...@zii.aero>
> Cc: Chris Healy <cphe...@gmail.com>
> Cc: Lucas Stach <l.st...@pengutronix.de>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-ker...@vger.kernel.org
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 30 +++++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c 
> b/drivers/gpu/drm/bridge/tc358767.c
> index 7d0fbb12195b..4bb9b15e1324 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -145,6 +145,8 @@
>  
>  /* AUX channel */
>  #define DP0_AUXCFG0          0x0660
> +#define DP0_AUXCFG0_BSIZE    GENMASK(11, 8)
> +#define DP0_AUXCFG0_ADDR_ONLY        BIT(4)
>  #define DP0_AUXCFG1          0x0664
>  #define AUX_RX_FILTER_EN             BIT(16)
>  
> @@ -327,6 +329,18 @@ static int tc_aux_read_data(struct tc_data *tc, void 
> *data, size_t size)
>       return size;
>  }
>  
> +static u32 tc_auxcfg0(struct drm_dp_aux_msg *msg, size_t size)
> +{
> +     u32 auxcfg0 = msg->request;
> +
> +     if (size)
> +             auxcfg0 |= FIELD_PREP(DP0_AUXCFG0_BSIZE, size - 1);
> +     else
> +             auxcfg0 |= DP0_AUXCFG0_ADDR_ONLY;
> +
> +     return auxcfg0;
> +}
> +
>  static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>                              struct drm_dp_aux_msg *msg)
>  {
> @@ -336,9 +350,6 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>       u32 auxstatus;
>       int ret;
>  
> -     if (size == 0)
> -             return 0;
> -
>       ret = tc_aux_wait_busy(tc, 100);
>       if (ret)
>               return ret;
> @@ -362,8 +373,7 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>       if (ret)
>               return ret;
>       /* Start transfer */
> -     ret = regmap_write(tc->regmap, DP0_AUXCFG0,
> -                        ((size - 1) << 8) | request);
> +     ret = regmap_write(tc->regmap, DP0_AUXCFG0, tc_auxcfg0(msg, size));
>       if (ret)
>               return ret;
>  
> @@ -377,8 +387,14 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>  
>       if (auxstatus & AUX_TIMEOUT)
>               return -ETIMEDOUT;
> -
> -     size = FIELD_GET(AUX_BYTES, auxstatus);
> +     /*
> +      * For some reason address-only DP_AUX_I2C_WRITE (MOT), still
> +      * reports 1 byte transferred in its status. To deal we that
> +      * we ignore aux_bytes field if we know that this was an
> +      * address-only transfer
> +      */
> +     if (size)
> +             size = FIELD_GET(AUX_BYTES, auxstatus);
>       msg->reply = FIELD_GET(AUX_STATUS, auxstatus);
>  
>       switch (request) {


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