On Fri, Jun 03, 2016 at 03:36:48PM +0100, Chris Wilson wrote:
> Rather than have both drm_dp_aux lock within its transfer, and i2c to
> lock around the transfer, use the same lock by filling in the locking
> callbacks that i2c wants to use. We require our own hw_mutex as we
> bypass i2c_transfer for drm_dp_dpcd_access().
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> Cc: Rafael Antognolli <rafael.antognolli@xxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> ---
> drivers/gpu/drm/drm_dp_helper.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index eeaf5a7c3aa7..4b088afa21b2 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -708,8 +708,6 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>
> memset(&msg, 0, sizeof(msg));
>
> - mutex_lock(&aux->hw_mutex);
> -
> for (i = 0; i < num; i++) {
> msg.address = msgs[i].addr;
> drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> @@ -764,8 +762,6 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> msg.size = 0;
> (void)drm_dp_i2c_do_msg(aux, &msg);
>
> - mutex_unlock(&aux->hw_mutex);
> -
> return err;
> }
AFAICS the only functional difference will be that we'll hold the lock
across the retries performed by the core. Looks like we set the retry
count to 3 for whatever reason, but I'm not seeing that we'd ever
actually return -EAGAIN so I guess the core will neever retry.
Oh, actually if we ever end up in the trylock path
(in_atomic||irqs_disabled) then the core would retry. But I don't think
we should ever do that.
Patch seems OK to me:
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> @@ -774,6 +770,26 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
> .master_xfer = drm_dp_i2c_xfer,
> };
>
> +static struct drm_dp_aux *i2c_to_aux(struct i2c_adapter *i2c)
> +{
> + return container_of(i2c, struct drm_dp_aux, ddc);
> +}
> +
> +static void lock_bus(struct i2c_adapter *i2c, unsigned int flags)
> +{
> + mutex_lock(&i2c_to_aux(i2c)->hw_mutex);
> +}
> +
> +static int trylock_bus(struct i2c_adapter *i2c, unsigned int flags)
> +{
> + return mutex_trylock(&i2c_to_aux(i2c)->hw_mutex);
> +}
> +
> +static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
> +{
> + mutex_unlock(&i2c_to_aux(i2c)->hw_mutex);
> +}
> +
> /**
> * drm_dp_aux_register() - initialise and register aux channel
> * @aux: DisplayPort AUX channel
> @@ -790,6 +806,10 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
> aux->ddc.algo_data = aux;
> aux->ddc.retries = 3;
>
> + aux->ddc.lock_bus = lock_bus;
> + aux->ddc.trylock_bus = trylock_bus;
> + aux->ddc.unlock_bus = unlock_bus;
> +
> aux->ddc.class = I2C_CLASS_DDC;
> aux->ddc.owner = THIS_MODULE;
> aux->ddc.dev.parent = aux->dev;
> --
> 2.8.1
--
Ville Syrjälä
Intel OTC
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