On Fri, 03 Feb 2017 15:54:33 +0100,
Ville Syrjälä wrote:
>
> On Fri, Feb 03, 2017 at 02:32:37PM +0100, Takashi Iwai wrote:
> > On Thu, 02 Feb 2017 11:12:53 +0100,
> > Takashi Iwai wrote:
> > >
> > > The audio chicken bit (register offset 0x62f38) seems required to make
> > > DP audio working on some machines. At least, on Dell Wyse 3040, I
> > > failed to get the audio unless this bit is set once.
> > >
> > > Strangely, the bit seems necessary only once, and it persists after
> > > that, even some power-off cycles. The register is supposedly
> > > write-only, so it's no evidence whether the bit keeps effect
> > > persistently. But, judging from the experiment, it looks enough to
> > > set it up once at the device initialization.
> > >
> > > The patch is basically a cut from the original patch by Pierre-Louis
> > > Bossart.
> > >
> > > Cc: Pierre-Louis Bossart <pierre-louis.boss...@linux.intel.com>
> > > Signed-off-by: Takashi Iwai <ti...@suse.de>
> >
> > I gave a typo to intel-gfx ML address, now corrected, sorry.
> >
> > Are you i915 guys OK with this change? I'd love to fix it for 4.11 in
> > time, so please check and give ACK.
> >
> >
> > thanks,
> >
> > Takashi
> >
> > > ---
> > > drivers/gpu/drm/i915/i915_reg.h | 3 +++
> > > drivers/gpu/drm/i915/intel_lpe_audio.c | 7 +++++++
> > > 2 files changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > > b/drivers/gpu/drm/i915/i915_reg.h
> > > index 4e24ba0cdbe8..4f15a3dc6d98 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -2062,6 +2062,9 @@ enum skl_disp_power_wells {
> > > #define I915_HDMI_LPE_AUDIO_SIZE 0x1000
> > >
> > > /* DisplayPort Audio w/ LPE */
> > > +#define VLV_AUD_CHICKEN_BIT_REG _MMIO(VLV_DISPLAY_BASE +
> > > 0x62F38)
> > > +#define VLV_CHICKEN_BIT_DBG_ENABLE (1 << 0)
> > > +
> > > #define _VLV_AUD_PORT_EN_B_DBG (VLV_DISPLAY_BASE + 0x62F20)
> > > #define _VLV_AUD_PORT_EN_C_DBG (VLV_DISPLAY_BASE + 0x62F30)
> > > #define _VLV_AUD_PORT_EN_D_DBG (VLV_DISPLAY_BASE + 0x62F34)
> > > diff --git a/drivers/gpu/drm/i915/intel_lpe_audio.c
> > > b/drivers/gpu/drm/i915/intel_lpe_audio.c
> > > index d3ffe0012692..3ba2799e93bd 100644
> > > --- a/drivers/gpu/drm/i915/intel_lpe_audio.c
> > > +++ b/drivers/gpu/drm/i915/intel_lpe_audio.c
> > > @@ -248,6 +248,13 @@ static int lpe_audio_setup(struct drm_i915_private
> > > *dev_priv)
> > > goto err_free_irq;
> > > }
> > >
> > > + /* enable chicken bit; at least this is required for Dell Wyse 3040
> > > + * with DP outputs (but only sometimes by some reason!)
> > > + */
> > > + I915_WRITE(VLV_AUD_CHICKEN_BIT_REG,
> > > + I915_READ(VLV_AUD_CHICKEN_BIT_REG) |
> > > + VLV_CHICKEN_BIT_DBG_ENABLE);
>
> RMW seems a little pointless since you verified that the register can't
> actually be read.
Indeed.
> So, with the read dropped
> Reviewed-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
Thanks!
Takashi
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