Re: [PATCH v3 09/14] drm/msm/dp: use msm_dp_utils_pack_sdp_header() for audio packets

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

On 12/12/2024 2:28 PM, Dmitry Baryshkov wrote:
> On Thu, 12 Dec 2024 at 23:41, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > On 12/11/2024 3:41 PM, Dmitry Baryshkov wrote:
> > > Use msm_dp_utils_pack_sdp_header() and call msm_dp_write_link() directly
> > > to program audio packet data. Use 0 as Packet ID, as it was not
> > > programmed earlier.
> > >
> > > Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/dp/dp_audio.c | 288 +++++++++-----------------------------
> > >    1 file changed, 66 insertions(+), 222 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/dp/dp_audio.c b/drivers/gpu/drm/msm/dp/dp_audio.c
> > > index 5cbb11986460d1e4ed1890bdf66d0913e013083c..1aa52d5cc08684a49102e45ed6e40ac2b13497c7 100644
> > > --- a/drivers/gpu/drm/msm/dp/dp_audio.c
> > > +++ b/drivers/gpu/drm/msm/dp/dp_audio.c
> > > @@ -14,6 +14,7 @@
> > >    #include "dp_catalog.h"
> > >    #include "dp_audio.h"
> > >    #include "dp_panel.h"
> > > +#include "dp_reg.h"
> > >    #include "dp_display.h"
> > >    #include "dp_utils.h"
> > >
> > > @@ -28,251 +29,94 @@ struct msm_dp_audio_private {
> > >        struct msm_dp_audio msm_dp_audio;
> > >    };
> > >
> > > -static u32 msm_dp_audio_get_header(struct msm_dp_catalog *catalog,
> > > -             enum msm_dp_catalog_audio_sdp_type sdp,
> > > -             enum msm_dp_catalog_audio_header_type header)
> > > -{
> > > -     return msm_dp_catalog_audio_get_header(catalog, sdp, header);
> > > -}
> > > -
> > > -static void msm_dp_audio_set_header(struct msm_dp_catalog *catalog,
> > > -             u32 data,
> > > -             enum msm_dp_catalog_audio_sdp_type sdp,
> > > -             enum msm_dp_catalog_audio_header_type header)
> > > -{
> > > -     msm_dp_catalog_audio_set_header(catalog, sdp, header, data);
> > > -}
> > > -
> > >    static void msm_dp_audio_stream_sdp(struct msm_dp_audio_private *audio)
> > >    {
> > >        struct msm_dp_catalog *catalog = audio->catalog;
> > > -     u32 value, new_value;
> > > -     u8 parity_byte;
> > > -
> > > -     /* Config header and parity byte 1 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     new_value = 0x02;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_1_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_1_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 1: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     /* Config header and parity byte 2 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_2);
> > > -     new_value = value;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_2_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_2_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 2: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     /* Config header and parity byte 3 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_3);
> > > -
> > > -     new_value = audio->channels - 1;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_3_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_3_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 3: value = 0x%x, parity_byte = 0x%x\n",
> > > -             value, parity_byte);
> > > -
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_STREAM, DP_AUDIO_SDP_HEADER_3);
> > > +     struct dp_sdp_header sdp_hdr = {
> > > +             .HB0 = 0x00,
> > > +             .HB1 = 0x02,
> > > +             .HB2 = 0x00,
> > > +             .HB3 = audio->channels - 1,
> > > +     };
> > > +     u32 header[2];
> > > +
> > > +     msm_dp_utils_pack_sdp_header(&sdp_hdr, header);
> > > +
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_STREAM_0, header[0]);
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_STREAM_1, header[1]);
> > >    }
> >
> > This patch is changing the programming behavior.
> >
> > Earlier it was using a read/modify/write on each register. Now, its just
> >    a write. I checked a few chipsets, the reset value of registers was 0,
> > so that part is okay.
>
> Except that it was not a correct RMW, it was read, OR new data without
> clearing the bitfield, write. So it has been working mostly by a
> miracle,
>
> > But, for the MMSS_DP_AUDIO_STREAM_0 register, earlier we were writing
> > only the upper nibble, that is bits 15:0 of DP_AUDIO_SDP_HEADER_0 was
> > kept as-it-is, but now this patch is changing that to 0. What was the
> > reason for that change?
>
> It is described in the commit message: "Use 0 as Packet ID, as it was not
> programmed earlier."

The part of using 0 as Packet ID is but not the behavior of changing the 
RMW which is also pretty significant. That was all happening under the hood.

> > This is true for all the APIs being touched in this file.
> >
> > I guess the whole point of having that audio map in the catalog was to
> > preserve the read values of these registers. I have to check what was
> > the reason behind that as once again this was before I worked on this
> > driver as well.
> >
> > So technically there are two parts to this change:
> >
> > 1) dropping read for each header and directly just writing it
> > 2) Writing the registers directly instead of going through catalog
> >
> > It seems like (1) and (2) are independent. I hope (1) was not the reason
> > to have started this whole rework.
>
> Yes, the driver spends a lot of effort to preserve the data that will
> be rewritten when the function is called to write the next header
> byte. So it is useless. Only HB0 has been preserved, PacketID. If for
> some reason we are generating a stream with the non-zero ID, it should
> be explicit, not implicitly 'preserved'.

I am trying to understand why this was being preserved. Audio 
programming is half in DP driver and half in ADSP. I dont know if the 
expectation was that packet ID will be programmed elsewhere and not in 
HLOS code hence it was preserved.

> So, the reasons were:
> - fix the RMW cycles to drop old values from the registers
> - use new msm_dp_utils_pack_sdp_header()
> - get rid of the useless indirection through the catalog and enum
> msm_dp_catalog_audio_header_type
> - write registers in an efficient way.
> - if we ever have a set of functions to handle DP infoframes (like we
> do for HDMI), make the MSM DP driver ready to be converted to such
> functions.


The only reason the current driver needed to go through the catalog map 
was that it was trying to write one header at a time. And in the 
registers, 2 headers are mapped to one register. So a map was needed. I 
do not know the reason for breaking up the writes into one header at a 
time like I already mentioned so I am trying to gather that info. 
Without knowing the reason it might seem useless but its my duty to make 
sure nothing was overlooked.



> > >    static void msm_dp_audio_timestamp_sdp(struct msm_dp_audio_private *audio)
> > >    {
> > >        struct msm_dp_catalog *catalog = audio->catalog;
> > > -     u32 value, new_value;
> > > -     u8 parity_byte;
> > > -
> > > -     /* Config header and parity byte 1 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     new_value = 0x1;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_1_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_1_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 1: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     /* Config header and parity byte 2 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     new_value = 0x17;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_2_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_2_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 2: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     /* Config header and parity byte 3 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_3);
> > > -
> > > -     new_value = (0x0 | (0x11 << 2));
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_3_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_3_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 3: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_TIMESTAMP, DP_AUDIO_SDP_HEADER_3);
> > > +     struct dp_sdp_header sdp_hdr = {
> > > +             .HB0 = 0x00,
> > > +             .HB1 = 0x01,
> > > +             .HB2 = 0x17,
> > > +             .HB3 = 0x0 | (0x11 << 2),
> > > +     };
> > > +     u32 header[2];
> > > +
> > > +     msm_dp_utils_pack_sdp_header(&sdp_hdr, header);
> > > +
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_TIMESTAMP_0, header[0]);
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_TIMESTAMP_1, header[1]);
> > >    }
> > >
> > >    static void msm_dp_audio_infoframe_sdp(struct msm_dp_audio_private *audio)
> > >    {
> > >        struct msm_dp_catalog *catalog = audio->catalog;
> > > -     u32 value, new_value;
> > > -     u8 parity_byte;
> > > -
> > > -     /* Config header and parity byte 1 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     new_value = 0x84;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_1_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_1_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 1: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     /* Config header and parity byte 2 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     new_value = 0x1b;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_2_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_2_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 2: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     /* Config header and parity byte 3 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_3);
> > > -
> > > -     new_value = (0x0 | (0x11 << 2));
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_3_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_3_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 3: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     new_value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_INFOFRAME, DP_AUDIO_SDP_HEADER_3);
> > > +     struct dp_sdp_header sdp_hdr = {
> > > +             .HB0 = 0x00,
> > > +             .HB1 = 0x84,
> > > +             .HB2 = 0x1b,
> > > +             .HB3 = 0x0 | (0x11 << 2),
> > > +     };
> > > +     u32 header[2];
> > > +
> > > +     msm_dp_utils_pack_sdp_header(&sdp_hdr, header);
> > > +
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_INFOFRAME_0, header[0]);
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_INFOFRAME_1, header[1]);
> > >    }
> > >
> > >    static void msm_dp_audio_copy_management_sdp(struct msm_dp_audio_private *audio)
> > >    {
> > >        struct msm_dp_catalog *catalog = audio->catalog;
> > > -     u32 value, new_value;
> > > -     u8 parity_byte;
> > > -
> > > -     /* Config header and parity byte 1 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     new_value = 0x05;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_1_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_1_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 1: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     /* Config header and parity byte 2 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     new_value = 0x0F;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_2_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_2_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 2: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     /* Config header and parity byte 3 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_3);
> > > -
> > > -     new_value = 0x0;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_3_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_3_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 3: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_COPYMANAGEMENT, DP_AUDIO_SDP_HEADER_3);
> > > +     struct dp_sdp_header sdp_hdr = {
> > > +             .HB0 = 0x00,
> > > +             .HB1 = 0x05,
> > > +             .HB2 = 0x0f,
> > > +             .HB3 = 0x00,
> > > +     };
> > > +     u32 header[2];
> > > +
> > > +     msm_dp_utils_pack_sdp_header(&sdp_hdr, header);
> > > +
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_COPYMANAGEMENT_0, header[0]);
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_COPYMANAGEMENT_1, header[1]);
> > >    }
> > >
> > >    static void msm_dp_audio_isrc_sdp(struct msm_dp_audio_private *audio)
> > >    {
> > >        struct msm_dp_catalog *catalog = audio->catalog;
> > > -     u32 value, new_value;
> > > -     u8 parity_byte;
> > > -
> > > -     /* Config header and parity byte 1 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_ISRC, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     new_value = 0x06;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_1_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_1_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 1: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_ISRC, DP_AUDIO_SDP_HEADER_1);
> > > -
> > > -     /* Config header and parity byte 2 */
> > > -     value = msm_dp_audio_get_header(catalog,
> > > -                     DP_AUDIO_SDP_ISRC, DP_AUDIO_SDP_HEADER_2);
> > > -
> > > -     new_value = 0x0F;
> > > -     parity_byte = msm_dp_utils_calculate_parity(new_value);
> > > -     value |= ((new_value << HEADER_BYTE_2_BIT)
> > > -                     | (parity_byte << PARITY_BYTE_2_BIT));
> > > -     drm_dbg_dp(audio->drm_dev,
> > > -                     "Header Byte 2: value = 0x%x, parity_byte = 0x%x\n",
> > > -                     value, parity_byte);
> > > -     msm_dp_audio_set_header(catalog, value,
> > > -             DP_AUDIO_SDP_ISRC, DP_AUDIO_SDP_HEADER_2);
> > > +     struct dp_sdp_header sdp_hdr = {
> > > +             .HB0 = 0x00,
> > > +             .HB1 = 0x06,
> > > +             .HB2 = 0x0f,
> > > +             .HB3 = 0x00,
> > > +     };
> > > +     u32 header[2];
> > > +     u32 reg;
> > > +
> > > +     /* XXX: is it necessary to preserve this field? */
> > > +     reg = msm_dp_read_link(catalog, MMSS_DP_AUDIO_ISRC_1);
> > > +     sdp_hdr.HB3 = FIELD_GET(HEADER_3_MASK, reg);
> > > +
> > > +     msm_dp_utils_pack_sdp_header(&sdp_hdr, header);
> > > +
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_ISRC_0, header[0]);
> > > +     msm_dp_write_link(catalog, MMSS_DP_AUDIO_ISRC_1, header[1]);
> > >    }
> > >
> > >    static void msm_dp_audio_setup_sdp(struct msm_dp_audio_private *audio)