Subject: Re: [PATCH] drm: bridge/dw_hdmi: add audio sample channel status setting

From: Russell King - ARM Linux admin <[email-masked]>
Date: Wed, 4 Sep 2019 11:31:50 +0100

On Wed, Sep 04, 2019 at 05:45:20PM +0800, Cheng-yi Chiang wrote:
> On Wed, Sep 4, 2019 at 5:28 PM Neil Armstrong <[email-masked]> wrote:
> >
> > Hi,
> >
> > On 04/09/2019 11:09, Cheng-yi Chiang wrote:
> > > Hi,
> > >
> > > On Tue, Sep 3, 2019 at 5:53 PM Neil Armstrong <[email-masked]> wrote:
> > >>
> > >> Hi,
> > >>
> > >> On 03/09/2019 07:51, Cheng-Yi Chiang wrote:
> > >>> From: Yakir Yang <[email-masked]>
> > >>>
> > >>> When transmitting IEC60985 linear PCM audio, we configure the
> > >>> Audio Sample Channel Status information of all the channel
> > >>> status bits in the IEC60958 frame.
> > >>> Refer to 60958-3 page 10 for frequency, original frequency, and
> > >>> wordlength setting.
> > >>>
> > >>> This fix the issue that audio does not come out on some monitors
> > >>> (e.g. LG 22CV241)
> > >>>
> > >>> Signed-off-by: Yakir Yang <[email-masked]>
> > >>> Signed-off-by: Cheng-Yi Chiang <[email-masked]>
> > >>> ---
> > >>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 59 +++++++++++++++++++++++
> > >>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.h | 20 ++++++++
> > >>>  2 files changed, 79 insertions(+)
> > >>>
> > >>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > >>> index bd65d0479683..34d46e25d610 100644
> > >>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > >>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > >>> @@ -582,6 +582,63 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk)
> > >>>       return n;
> > >>>  }
> > >>>
> > >>> +static void hdmi_set_schnl(struct dw_hdmi *hdmi)
> > >>> +{
> > >>> +     u8 aud_schnl_samplerate;
> > >>> +     u8 aud_schnl_8;
> > >>> +
> > >>> +     /* These registers are on RK3288 using version 2.0a. */
> > >>> +     if (hdmi->version != 0x200a)
> > >>> +             return;
> > >>
> > >> Are these limited to the 2.0a version *in* RK3288, or 2.0a version on all
> > >> SoCs ?
> > >>
> > >
> > > In the original patch by Yakir,
> > >
> > > https://lore.kernel.org/patchwork/patch/539653/   (sorry, I should
> > > have added this link in the "after the cut" note)
> > >
> > > The fix is limited to version 2.0.
> > > Since I am only testing on RK3288 with 2.0a, I change the check to 2.0a only.
> > > I can not test 2.0a version on other SoCs.
> > > The databook I have at hand is 2.0a (not specific to RK3288) so I
> > > think all 2.0a should have this register.
> > >
> > > As for other version like version 1.3 on iMX6, there is no such
> > > register, as stated by Russell
> > >
> > > http://lkml.iu.edu/hypermail/linux/kernel/1501.3/06268.html.
> >
> > Russell assumes the registers are not present on the iMX6 IP not having
> > the I2S registers, but they are present on the IPs configured with I2S
> > at any versions.
> 
> I see. Thanks for the check.
> 
> >
> > My databook version (1.40.a) specifies :
> >
> > fc_audschnls0 to fc_audschnls8
> >
> > ```
> > When transmitting IEC60958 linear PCM audio, this registers allow to configure the channel status
> > information of all the channel status bits in the IEC60958 frame. For the moment this configuration is only
> > used when the I2S audio interface, General Purpose Audio (GPA), or AHB audio DMA (AHBAUDDMA)
> > interface is active (for S/PDIF interface this information comes from the stream).
> > ```
> >
> > But the databook Revision History shows these registers were present since version 1.10a.
> >
> > I propose you remove the version check, but you only setup these registers when I2S is enabled:
> > (hdmi_readb(hdmi, HDMI_CONFIG0_ID) & HDMI_CONFIG0_I2S) until a AHBAUDDMA user needs this,
> > with a small comment explaining the situation.
> 
> I see. Sound like a good plan.
> In sum, I will add
> set_channel_status()
> in dw_hdmi.c
> And in the beginning of this function,
> check it is using I2S
>  (hdmi_readb(hdmi, HDMI_CONFIG0_ID) & HDMI_CONFIG0_I2S)
> with a comment explaining the situation.
> 
> And let dw-hdmi-audio-i2s dw_hdmi_i2s_hw_params() to call this
> function after dw_hdmi_set_sample_rate, with word length (or
> sample_bit) passed it as argument.

If you're going to do it this way, there's little point having the
check.  The dw-hdmi-audio-i2s device will only be created if that
ID bit is already set.  So, provided set_channel_status() (which
should probably be dw_hdmi_set_channel_status()) is only called from
the I2S driver, then everything should be fine without such a check.
However, it is worth noting in the docbook comments above the function
that it is only for I2S setups.

> I have not tested setting this register here as in the original patch
> it was set in hdmi_set_clk_regenerator.
> I will test it and update in my v2.
> 
> Thanks again to everyone for the prompt reply and help.
> 
> >
> > Neil
> >
> > >
> > > So at least we should check the version.
> > > Maybe we can set the criteria as version 2.0 or above to make it a safe patch ?
> > > If there is the same need on other SoC with version < 2.0, it can be
> > > added later.
> > > Presumably, there will be databook of that version to help confirming
> > > this setting.
> > >
> > > Thanks!
> > >>> +
> > >>> +     switch (hdmi->sample_rate) {
> > >>> +     case 32000:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_32K;
> > >>> +             break;
> > >>> +     case 44100:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_44K1;
> > >>> +             break;
> > >>> +     case 48000:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_48K;
> > >>> +             break;
> > >>> +     case 88200:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_88K2;
> > >>> +             break;
> > >>> +     case 96000:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_96K;
> > >>> +             break;
> > >>> +     case 176400:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_176K4;
> > >>> +             break;
> > >>> +     case 192000:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_192K;
> > >>> +             break;
> > >>> +     case 768000:
> > >>> +             aud_schnl_samplerate = HDMI_FC_AUDSCHNLS7_SMPRATE_768K;
> > >>> +             break;
> > >>> +     default:
> > >>> +             dev_warn(hdmi->dev, "Unsupported audio sample rate (%u)\n",
> > >>> +                      hdmi->sample_rate);
> > >>> +             return;
> > >>> +     }
> > >>> +
> > >>> +     /* set channel status register */
> > >>> +     hdmi_modb(hdmi, aud_schnl_samplerate, HDMI_FC_AUDSCHNLS7_SMPRATE_MASK,
> > >>> +               HDMI_FC_AUDSCHNLS7);
> > >>> +
> > >>> +     /*
> > >>> +      * Set original frequency to be the same as frequency.
> > >>> +      * Use one-complement value as stated in IEC60958-3 page 13.
> > >>> +      */
> > >>> +     aud_schnl_8 = (~aud_schnl_samplerate) <<
> > >>> +                     HDMI_FC_AUDSCHNLS8_ORIGSAMPFREQ_OFFSET;
> > >>> +
> > >>> +     /* This means word length is 16 bit. Refer to IEC60958-3 page 12. */
> > >>> +     aud_schnl_8 |= 2 << HDMI_FC_AUDSCHNLS8_WORDLEGNTH_OFFSET;
> > >>> +
> > >>> +     hdmi_writeb(hdmi, aud_schnl_8, HDMI_FC_AUDSCHNLS8);
> > >>> +}
> > >>> +
> > >>>  static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
> > >>>       unsigned long pixel_clk, unsigned int sample_rate)
> > >>>  {
> > >>> @@ -620,6 +677,8 @@ static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
> > >>>       hdmi->audio_cts = cts;
> > >>>       hdmi_set_cts_n(hdmi, cts, hdmi->audio_enable ? n : 0);
> > >>>       spin_unlock_irq(&hdmi->audio_lock);
> > >>> +
> > >>> +     hdmi_set_schnl(hdmi);
> > >>>  }
> > >>>
> > >>>  static void hdmi_init_clk_regenerator(struct dw_hdmi *hdmi)
> > >>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> > >>> index 6988f12d89d9..619ebc1c8354 100644
> > >>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> > >>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
> > >>> @@ -158,6 +158,17 @@
> > >>>  #define HDMI_FC_SPDDEVICEINF                    0x1062
> > >>>  #define HDMI_FC_AUDSCONF                        0x1063
> > >>>  #define HDMI_FC_AUDSSTAT                        0x1064
> > >>> +#define HDMI_FC_AUDSV                           0x1065
> > >>> +#define HDMI_FC_AUDSU                           0x1066
> > >>> +#define HDMI_FC_AUDSCHNLS0                      0x1067
> > >>> +#define HDMI_FC_AUDSCHNLS1                      0x1068
> > >>> +#define HDMI_FC_AUDSCHNLS2                      0x1069
> > >>> +#define HDMI_FC_AUDSCHNLS3                      0x106a
> > >>> +#define HDMI_FC_AUDSCHNLS4                      0x106b
> > >>> +#define HDMI_FC_AUDSCHNLS5                      0x106c
> > >>> +#define HDMI_FC_AUDSCHNLS6                      0x106d
> > >>> +#define HDMI_FC_AUDSCHNLS7                      0x106e
> > >>> +#define HDMI_FC_AUDSCHNLS8                      0x106f
> > >>>  #define HDMI_FC_DATACH0FILL                     0x1070
> > >>>  #define HDMI_FC_DATACH1FILL                     0x1071
> > >>>  #define HDMI_FC_DATACH2FILL                     0x1072
> > >>> @@ -706,6 +717,15 @@ enum {
> > >>>  /* HDMI_FC_AUDSCHNLS7 field values */
> > >>>       HDMI_FC_AUDSCHNLS7_ACCURACY_OFFSET = 4,
> > >>>       HDMI_FC_AUDSCHNLS7_ACCURACY_MASK = 0x30,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_MASK = 0x0f,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_192K = 0xe,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_176K4 = 0xc,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_96K = 0xa,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_768K = 0x9,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_88K2 = 0x8,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_32K = 0x3,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_48K = 0x2,
> > >>> +     HDMI_FC_AUDSCHNLS7_SMPRATE_44K1 = 0x0,
> > >>>
> > >>>  /* HDMI_FC_AUDSCHNLS8 field values */
> > >>>       HDMI_FC_AUDSCHNLS8_ORIGSAMPFREQ_MASK = 0xf0,
> > >>>
> > >>
> >
> 
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