Re: [PATCH 03/10] drm/msm/dsi: Zero-terminate msm_dsi_config::io_start

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 13/02/2023 11:18, Konrad Dybcio wrote:
> On 11.02.2023 14:19, Dmitry Baryshkov wrote:
> > On 11/02/2023 13:51, Konrad Dybcio wrote:
> > > In preparation for supporting multiple sets of possible base registers,
> > > Zero-terminate the array that contains them to remove the need of
> > > specifying num_dsi for each set.
> > >
> > > Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/dsi/dsi_cfg.c  | 39 ++++++++++--------------------
> > >    drivers/gpu/drm/msm/dsi/dsi_cfg.h  |  4 +--
> > >    drivers/gpu/drm/msm/dsi/dsi_host.c |  2 +-
> > >    3 files changed, 16 insertions(+), 29 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_cfg.c b/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> > > index 068d45b3a8f0..5f62c563bd1c 100644
> > > --- a/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> > > +++ b/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> > > @@ -22,9 +22,8 @@ static const struct msm_dsi_config apq8064_dsi_cfg = {
> > >        .bus_clk_names = dsi_v2_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_v2_bus_clk_names),
> > >        .io_start = {
> > > -        { 0x4700000, 0x5800000 },
> > > +        { 0x4700000, 0x5800000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_6g_bus_clk_names[] = {
> > > @@ -44,9 +43,8 @@ static const struct msm_dsi_config msm8974_apq8084_dsi_cfg = {
> > >        .bus_clk_names = dsi_6g_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_6g_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xfd922800, 0xfd922b00 },
> > > +        { 0xfd922800, 0xfd922b00, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_8916_bus_clk_names[] = {
> > > @@ -65,9 +63,8 @@ static const struct msm_dsi_config msm8916_dsi_cfg = {
> > >        .bus_clk_names = dsi_8916_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_8916_bus_clk_names),
> > >        .io_start = {
> > > -        { 0x1a98000 },
> > > +        { 0x1a98000, 0 },
> > >        },
> > > -    .num_dsi = 1,
> > >    };
> > >      static const char * const dsi_8976_bus_clk_names[] = {
> > > @@ -86,9 +83,8 @@ static const struct msm_dsi_config msm8976_dsi_cfg = {
> > >        .bus_clk_names = dsi_8976_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_8976_bus_clk_names),
> > >        .io_start = {
> > > -        { 0x1a94000, 0x1a96000 },
> > > +        { 0x1a94000, 0x1a96000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const struct regulator_bulk_data msm8994_dsi_regulators[] = {
> > > @@ -107,9 +103,8 @@ static const struct msm_dsi_config msm8994_dsi_cfg = {
> > >        .bus_clk_names = dsi_6g_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_6g_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xfd998000, 0xfd9a0000 },
> > > +        { 0xfd998000, 0xfd9a0000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_8996_bus_clk_names[] = {
> > > @@ -129,9 +124,8 @@ static const struct msm_dsi_config msm8996_dsi_cfg = {
> > >        .bus_clk_names = dsi_8996_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_8996_bus_clk_names),
> > >        .io_start = {
> > > -        { 0x994000, 0x996000 },
> > > +        { 0x994000, 0x996000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_msm8998_bus_clk_names[] = {
> > > @@ -150,9 +144,8 @@ static const struct msm_dsi_config msm8998_dsi_cfg = {
> > >        .bus_clk_names = dsi_msm8998_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_msm8998_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xc994000, 0xc996000 },
> > > +        { 0xc994000, 0xc996000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_sdm660_bus_clk_names[] = {
> > > @@ -170,9 +163,8 @@ static const struct msm_dsi_config sdm660_dsi_cfg = {
> > >        .bus_clk_names = dsi_sdm660_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_sdm660_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xc994000, 0xc996000 },
> > > +        { 0xc994000, 0xc996000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_sdm845_bus_clk_names[] = {
> > > @@ -194,9 +186,8 @@ static const struct msm_dsi_config sdm845_dsi_cfg = {
> > >        .bus_clk_names = dsi_sdm845_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_sdm845_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xae94000, 0xae96000 },
> > > +        { 0xae94000, 0xae96000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const struct regulator_bulk_data sm8550_dsi_regulators[] = {
> > > @@ -210,9 +201,8 @@ static const struct msm_dsi_config sm8550_dsi_cfg = {
> > >        .bus_clk_names = dsi_sdm845_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_sdm845_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xae94000, 0xae96000 },
> > > +        { 0xae94000, 0xae96000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const struct regulator_bulk_data sc7180_dsi_regulators[] = {
> > > @@ -226,9 +216,8 @@ static const struct msm_dsi_config sc7180_dsi_cfg = {
> > >        .bus_clk_names = dsi_sc7180_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_sc7180_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xae94000 },
> > > +        { 0xae94000, 0 },
> > >        },
> > > -    .num_dsi = 1,
> > >    };
> > >      static const char * const dsi_sc7280_bus_clk_names[] = {
> > > @@ -246,9 +235,8 @@ static const struct msm_dsi_config sc7280_dsi_cfg = {
> > >        .bus_clk_names = dsi_sc7280_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_sc7280_bus_clk_names),
> > >        .io_start = {
> > > -        { 0xae94000, 0xae96000 },
> > > +        { 0xae94000, 0xae96000, 0 },
> > >        },
> > > -    .num_dsi = 2,
> > >    };
> > >      static const char * const dsi_qcm2290_bus_clk_names[] = {
> > > @@ -266,9 +254,8 @@ static const struct msm_dsi_config qcm2290_dsi_cfg = {
> > >        .bus_clk_names = dsi_qcm2290_bus_clk_names,
> > >        .num_bus_clks = ARRAY_SIZE(dsi_qcm2290_bus_clk_names),
> > >        .io_start = {
> > > -        { 0x5e94000 },
> > > +        { 0x5e94000, 0 },
> > >        },
> > > -    .num_dsi = 1,
> > >    };
> > >      static const struct msm_dsi_host_cfg_ops msm_dsi_v2_host_ops = {
> > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_cfg.h b/drivers/gpu/drm/msm/dsi/dsi_cfg.h
> > > index df9f09876ccb..03493cc6b772 100644
> > > --- a/drivers/gpu/drm/msm/dsi/dsi_cfg.h
> > > +++ b/drivers/gpu/drm/msm/dsi/dsi_cfg.h
> > > @@ -41,8 +41,8 @@ struct msm_dsi_config {
> > >        int num_regulators;
> > >        const char * const *bus_clk_names;
> > >        const int num_bus_clks;
> > > -    const resource_size_t io_start[VARIANTS_MAX][DSI_MAX];
> > > -    const int num_dsi;
> > > +    /* Allow + 1 entry for the zero-terminator */
> > > +    const resource_size_t io_start[VARIANTS_MAX][DSI_MAX + 1];
> > >    };
> > >      struct msm_dsi_host_cfg_ops {
> > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > index 22ba8726b0ea..f5092b4d0757 100644
> > > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > @@ -1868,7 +1868,7 @@ static int dsi_host_get_id(struct msm_dsi_host *msm_host)
> > >        if (!res)
> > >            return -EINVAL;
> > >    -    for (i = 0; i < cfg->num_dsi; i++) {
> > > +    for (i = 0; cfg->io_start[0][i]; i++) {
> > >            if (cfg->io_start[0][i] == res->start)
> > >                return i;
> > >        }
> >
> > I think we have the easier way to do this: always loop towards DSI_MAX. Empty cells will contain the value of 0 which can not match against valid starting address.
> Yep, your approach will save us NUM_ENTRIES*sizeof(u64) memory!

As for me it not about saving memory, but rather about the driver logic. 
Compare:
- We have two possible DSI hosts, one which is ocassionally absent thus 
the address is 0

vs

- We have a zero-terminated list of 2+1 entries for not more than two 
DSI hosts.

> > Also please shift this patch to the first place, it will be logical to add VARIANT_MAX after removing num_dsi.
> Ack.
>
> Konrad
> >

--
With best wishes
Dmitry