Re: [PATCH 6/7] drm/msm/dsi: Set PHY usescase before registering DSI host

[Dmitry Baryshkov]

On Wed, 17 Apr 2024 at 02:57, Marijn Suijten
<marijn.suijten@xxxxxxxxxxxxxx> wrote:
>
> Ordering issues here cause an uninitalized (default STANDALONE)
> usecase to be programmed (which appears to be a MUX) in some cases
> when msm_dsi_host_register() is called, leading to the slave PLL in
> bonded-DSI mode to source from a clock parent (dsi1vco) that is off.
>
> This should seemingly not be a problem as the actual dispcc clocks from
> DSI1 that are muxed in the clock tree of DSI0 are way further down, this
> bit still seems to have an effect on them somehow and causes the right
> side of the panel controlled by DSI1 to not function.
>
> In an ideal world this code is refactored to no longer have such
> error-prone calls "across subsystems", and instead model the "PLL src"
> register field as a regular mux so that changing the clock parents
> programmatically or in DTS via `assigned-clock-parents` has the
> desired effect.
> But for the avid reader, the clocks that we *are* muxing into DSI0's
> tree are way further down, so if this bit turns out to be a simple mux
> between dsiXvco and out_div, that shouldn't have any effect as this
> whole tree is off anyway.
>
> Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_manager.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index af2a287cb3bd..17f43b3c0494 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -85,6 +85,17 @@ static int dsi_mgr_setup_components(int id)
>                                                         msm_dsi : other_dsi;
>                 struct msm_dsi *slave_link_dsi = IS_MASTER_DSI_LINK(id) ?
>                                                         other_dsi : msm_dsi;
> +
> +               /* PLL0 is to drive both 2 DSI link clocks in bonded DSI mode.
> +                *
> +                * Set the usecase before calling msm_dsi_host_register() to prevent it from
> +                * enabling and configuring the usecase (which is just a mux bit) first.
> +                */
> +               msm_dsi_phy_set_usecase(clk_master_dsi->phy,
> +                                       MSM_DSI_PHY_MASTER);
> +               msm_dsi_phy_set_usecase(clk_slave_dsi->phy,
> +                                       MSM_DSI_PHY_SLAVE);
> +
>                 /* Register slave host first, so that slave DSI device
>                  * has a chance to probe, and do not block the master
>                  * DSI device's probe.
> @@ -100,10 +111,6 @@ static int dsi_mgr_setup_components(int id)
>                         return ret;
>
>                 /* PLL0 is to drive both 2 DSI link clocks in bonded DSI mode. */
> -               msm_dsi_phy_set_usecase(clk_master_dsi->phy,
> -                                       MSM_DSI_PHY_MASTER);
> -               msm_dsi_phy_set_usecase(clk_slave_dsi->phy,
> -                                       MSM_DSI_PHY_SLAVE);
>                 msm_dsi_host_set_phy_mode(msm_dsi->host, msm_dsi->phy);
>                 msm_dsi_host_set_phy_mode(other_dsi->host, other_dsi->phy);

Please move msm_dsi_host_set_phy_mode() calls too. Also please update
the non-bonded case.

>         }
>
> --
> 2.44.0
>


-- 
With best wishes
Dmitry