On Mon, Feb 26, 2018 at 01:48:37PM -0800, José Roberto de Souza wrote:
> When PSR/PSR2/GTC is enabled hardware can do AUX transactions by it
> self, so lets use the mutex register that is available in gen9+ to
> avoid concurrent access by hardware and driver.
> Older gen handling will be done separated.
>
> Reference:
> https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-skl-vol12-display.pdf
> Page 198 - AUX programming sequence
>
> Cc: Rodrigo Vivi <[email protected]>
> Cc: Jani Nikula <[email protected]>
> Cc: Dhinakaran Pandiyan <[email protected]>
> Cc: Ville Syrjälä <[email protected]>
> Signed-off-by: José Roberto de Souza <[email protected]>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 9 ++++++++
> drivers/gpu/drm/i915/intel_dp.c | 47
> +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 56 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index eea5b2c537d4..f36e839b4b4f 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -5385,6 +5385,15 @@ enum {
> #define DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(c) (((c) - 1) << 5)
> #define DP_AUX_CH_CTL_SYNC_PULSE_SKL(c) ((c) - 1)
>
> +#define _DPA_AUX_CH_MUTEX (dev_priv->info.display_mmio_offset + 0x6402C)
> +#define _DPB_AUX_CH_MUTEX (dev_priv->info.display_mmio_offset + 0x6412C)
> +#define _DPC_AUX_CH_MUTEX (dev_priv->info.display_mmio_offset + 0x6422C)
> +#define _DPD_AUX_CH_MUTEX (dev_priv->info.display_mmio_offset + 0x6432C)
> +#define _DPF_AUX_CH_MUTEX (dev_priv->info.display_mmio_offset + 0x6452C)
> +#define DP_AUX_CH_MUTEX(port) _MMIO_PORT(port, _DPA_AUX_CH_MUTEX,
> _DPB_AUX_CH_MUTEX)
s/port/aux_ch
> +#define DP_AUX_CH_MUTEX_ENABLE (1 << 31)
> +#define DP_AUX_CH_MUTEX_STATUS (1 << 30)
> +
> /*
> * Computing GMCH M and N values for the Display Port link
> *
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 2c3eb90b9499..7004239e4c9e 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1081,6 +1081,42 @@ static uint32_t intel_dp_get_aux_send_ctl(struct
> intel_dp *intel_dp,
> aux_clock_divider);
> }
>
> +static bool intel_dp_aux_ch_trylock(struct intel_dp *intel_dp)
> +{
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct drm_i915_private *dev_priv =
> + to_i915(intel_dig_port->base.base.dev);
> +
> + if (INTEL_GEN(dev_priv) < 9)
> + return true;
> +
> + /* Spec says that mutex is acquired when status bit is read as unset,
> + * here waiting for 2msec(+-4 aux transactions) before give up.
> + */
> + if (intel_wait_for_register(dev_priv, DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> + DP_AUX_CH_MUTEX_STATUS, 0, 2)) {
> + DRM_DEBUG_KMS("aux channel %c locked for 2msec, timing out\n",
> + aux_ch_name(intel_dp->aux_ch));
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static void intel_dp_aux_ch_unlock(struct intel_dp *intel_dp)
> +{
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct drm_i915_private *dev_priv =
> + to_i915(intel_dig_port->base.base.dev);
> +
> + if (INTEL_GEN(dev_priv) < 9)
> + return;
> +
> + /* set the status bit releases the mutex + keeping mutex enabled */
> + I915_WRITE(DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> + DP_AUX_CH_MUTEX_ENABLE | DP_AUX_CH_MUTEX_STATUS);
> +}
> +
> static int
> intel_dp_aux_ch(struct intel_dp *intel_dp,
> const uint8_t *send, int send_bytes,
> @@ -1119,6 +1155,11 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
>
> intel_dp_check_edp(intel_dp);
>
> + if (!intel_dp_aux_ch_trylock(intel_dp)) {
> + ret = -EBUSY;
> + goto out_locked;
out_"locked" confused me here...
not sure about a better name...
maybe out_aux_unlocked ?! :/
> + }
> +
> /* Try to wait for any previous AUX channel activity */
> for (try = 0; try < 3; try++) {
> status = I915_READ_NOTRACE(ch_ctl);
> @@ -1248,6 +1289,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
>
> ret = recv_bytes;
> out:
> + intel_dp_aux_ch_unlock(intel_dp);
> +out_locked:
> pm_qos_update_request(&dev_priv->pm_qos, PM_QOS_DEFAULT_VALUE);
>
> if (vdd)
> @@ -1544,6 +1587,10 @@ intel_dp_aux_init(struct intel_dp *intel_dp)
> else
> intel_dp->get_aux_send_ctl = g4x_get_aux_send_ctl;
>
> + if (INTEL_GEN(dev_priv) >= 9)
> + I915_WRITE(DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> + DP_AUX_CH_MUTEX_ENABLE);
> +
Cool! I believe we are in a good shape now...
with s/port/aux_ch corrected and preferably with a better goto out name:
Reviewed-by: Rodrigo Vivi <[email protected]>
> drm_dp_aux_init(&intel_dp->aux);
>
> /* Failure to allocate our preferred name is not critical */
> --
> 2.16.2
>
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