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Message-ID: <460e0036-74b5-bccd-c11c-2573290012ae@linaro.org>
Date:   Tue, 15 Feb 2022 17:44:46 +0300
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Subject: Re: [PATCH] drm/msm/dpu: Disable boot loader configured data paths
Content-Language: en-GB
To:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc:     linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20220215043708.1256854-1-bjorn.andersson@linaro.org>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <20220215043708.1256854-1-bjorn.andersson@linaro.org>
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Precedence: bulk

On 15/02/2022 07:37, Bjorn Andersson wrote:
> It's typical for the bootloader to configure CTL_0 for the boot splash
> or EFIFB, but for non-DSI use cases the DPU driver tend to pick another
> CTL and the system might end up with two configured data paths producing
> data on the same INTF. In particular as the IOMMU configuration isn't
> retained from the bootloader one of the data paths will push underflow
> color, resulting in screen flickering.
> 
> Naturally the end goal would be to inherit the bootloader's
> configuration and provide the user with a glitch-free handover from the
> boot configuration to a running DPU.
> 
> But such effort will affect clocks, regulators, power-domains etc, and
> will take time to implement. So in the meantime this patch simply
> disables all the data paths, on platforms that has CTL_FETCH_ACTIVE, to
> avoid the graphical artifacts.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c | 13 +++++++++++++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h |  6 ++++++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c    |  2 ++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c     | 17 +++++++++++++++++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h     |  8 ++++++++
>   5 files changed, 46 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
> index 02da9ecf71f1..69d4849484fa 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
> @@ -357,6 +357,18 @@ static void dpu_hw_ctl_clear_all_blendstages(struct dpu_hw_ctl *ctx)
>   	DPU_REG_WRITE(c, CTL_FETCH_PIPE_ACTIVE, 0);
>   }
>   
> +static void dpu_hw_ctl_disable_boot_config(struct dpu_hw_ctl *ctx)
> +{
> +	if (ctx->caps->features & BIT(DPU_CTL_FETCH_ACTIVE)) {

I see that you are changing only CTL_FETCH_PIPE_ACTIVE. However it still 
seems like a hack.
What if instead we always disable boot config for all paths except CTL_0 
(or CTL_0 and CTL_1)?

> +		/*
> +		 * Disable the pipe fetch and trigger a start, to disable the
> +		 * data path
> +		 */
> +		DPU_REG_WRITE(&ctx->hw, CTL_FETCH_PIPE_ACTIVE, 0);
> +		DPU_REG_WRITE(&ctx->hw, CTL_START, 0x1);

What about video vs cmd modes?

> +	}
> +}
> +
>   static void dpu_hw_ctl_setup_blendstage(struct dpu_hw_ctl *ctx,
>   	enum dpu_lm lm, struct dpu_hw_stage_cfg *stage_cfg)
>   {
> @@ -590,6 +602,7 @@ static void _setup_ctl_ops(struct dpu_hw_ctl_ops *ops,
>   	ops->trigger_pending = dpu_hw_ctl_trigger_pending;
>   	ops->reset = dpu_hw_ctl_reset_control;
>   	ops->wait_reset_status = dpu_hw_ctl_wait_reset_status;
> +	ops->disable_boot_config = dpu_hw_ctl_disable_boot_config;
>   	ops->clear_all_blendstages = dpu_hw_ctl_clear_all_blendstages;
>   	ops->setup_blendstage = dpu_hw_ctl_setup_blendstage;
>   	ops->get_bitmask_sspp = dpu_hw_ctl_get_bitmask_sspp;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h
> index 806c171e5df2..c2734f6ab760 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h
> @@ -159,6 +159,12 @@ struct dpu_hw_ctl_ops {
>   	 */
>   	void (*clear_all_blendstages)(struct dpu_hw_ctl *ctx);
>   
> +	/**
> +	 * Disable the configuration setup by the bootloader
> +	 * @ctx	      : ctl path ctx pointer
> +	 */
> +	void (*disable_boot_config)(struct dpu_hw_ctl *ctx);
> +
>   	/**
>   	 * Configure layer mixer to pipe configuration
>   	 * @ctx       : ctl path ctx pointer
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index cedc631f8498..eef2f017031a 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -1107,6 +1107,8 @@ static int dpu_kms_hw_init(struct msm_kms *kms)
>   
>   	dpu_kms->rm_init = true;
>   
> +	dpu_rm_clear_boot_config(&dpu_kms->rm, dpu_kms->catalog);
> +
>   	dpu_kms->hw_mdp = dpu_hw_mdptop_init(MDP_TOP, dpu_kms->mmio,
>   					     dpu_kms->catalog);
>   	if (IS_ERR(dpu_kms->hw_mdp)) {
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index f9c83d6e427a..3365c5e41e28 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -4,6 +4,7 @@
>    */
>   
>   #define pr_fmt(fmt)	"[drm:%s] " fmt, __func__
> +#include <linux/delay.h>
>   #include "dpu_kms.h"
>   #include "dpu_hw_lm.h"
>   #include "dpu_hw_ctl.h"
> @@ -229,6 +230,22 @@ int dpu_rm_init(struct dpu_rm *rm,
>   	return rc ? rc : -EFAULT;
>   }
>   
> +void dpu_rm_clear_boot_config(struct dpu_rm *rm, struct dpu_mdss_cfg *cat)
> +{
> +	struct dpu_hw_ctl *ctl;
> +	int i;
> +
> +	for (i = CTL_0; i < CTL_MAX; i++) {
> +		if (!rm->ctl_blks[i - CTL_0])
> +			continue;
> +
> +		DPU_DEBUG("disabling ctl%d boot configuration\n", i - CTL_0);
> +
> +		ctl = to_dpu_hw_ctl(rm->ctl_blks[i - CTL_0]);
> +		ctl->ops.disable_boot_config(ctl);
> +	}
> +}
> +
>   static bool _dpu_rm_needs_split_display(const struct msm_display_topology *top)
>   {
>   	return top->num_intf > 1;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> index 1f12c8d5b8aa..d3e084541e67 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> @@ -88,5 +88,13 @@ void dpu_rm_release(struct dpu_global_state *global_state,
>   int dpu_rm_get_assigned_resources(struct dpu_rm *rm,
>   	struct dpu_global_state *global_state, uint32_t enc_id,
>   	enum dpu_hw_blk_type type, struct dpu_hw_blk **blks, int blks_size);
> +
> +/**
> + * dpu_rm_clear_boot_config() - Tear down any data paths configured by boot
> + * @rm: DPU Resource Manager handle
> + * @cat: Pointer to hardware catalog
> + */
> +void dpu_rm_clear_boot_config(struct dpu_rm *rm, struct dpu_mdss_cfg *cat);
> +
>   #endif /* __DPU_RM_H__ */
>   


-- 
With best wishes
Dmitry