linux-kernel - Re: [v2 1/3] drm/arm/mali-dp: Add display QoS interface configuration for Mali DP500

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Message-ID: <20190719114624.GB16673@e110455-lin.cambridge.arm.com>
Date:   Fri, 19 Jul 2019 12:46:24 +0100
From:   Liviu Dudau <liviu.dudau@....com>
To:     Wen He <wen.he_1@....com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        brian.starkey@....com, airlied@...ux.ie, daniel@...ll.ch,
        leoyang.li@....com
Subject: Re: [v2 1/3] drm/arm/mali-dp: Add display QoS interface
 configuration for Mali DP500

On Fri, Jul 19, 2019 at 05:54:45PM +0800, Wen He wrote:
> Configure the display Quality of service (QoS) levels priority if the
> optional property node "arm,malidp-aqros-value" is defined in DTS file.
> 
> QoS signaling using AQROS and AWQOS AXI interface signals, the AQROS is
> driven from the "RQOS" register, so needed to program the RQOS register
> to avoid the 4k resolution flicker issue on the LS1028A platform.
> 
> Signed-off-by: Wen He <wen.he_1@....com>
> ---
> change in v2:
>         - modify some content based on feedback from maintainers
> 
>  drivers/gpu/drm/arm/malidp_drv.c  |  6 ++++++
>  drivers/gpu/drm/arm/malidp_hw.c   | 13 +++++++++++++
>  drivers/gpu/drm/arm/malidp_hw.h   |  3 +++
>  drivers/gpu/drm/arm/malidp_regs.h | 10 ++++++++++
>  4 files changed, 32 insertions(+)
> 
> diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
> index f25ec4382277..61c49a0668a7 100644
> --- a/drivers/gpu/drm/arm/malidp_drv.c
> +++ b/drivers/gpu/drm/arm/malidp_drv.c
> @@ -818,6 +818,12 @@ static int malidp_bind(struct device *dev)
>  
>  	malidp->core_id = version;
>  
> +	ret = of_property_read_u32(dev->of_node,
> +					"arm,malidp-arqos-value",
> +					&hwdev->arqos_value);
> +	if (ret)
> +		hwdev->arqos_value = 0x0;

Is zero the default value that you want? I thought it was 0x00010001.

> +
>  	/* set the number of lines used for output of RGB data */
>  	ret = of_property_read_u8_array(dev->of_node,
>  					"arm,malidp-output-port-lines",
> diff --git a/drivers/gpu/drm/arm/malidp_hw.c b/drivers/gpu/drm/arm/malidp_hw.c
> index 50af399d7f6f..323683b1e9f7 100644
> --- a/drivers/gpu/drm/arm/malidp_hw.c
> +++ b/drivers/gpu/drm/arm/malidp_hw.c
> @@ -374,6 +374,19 @@ static void malidp500_modeset(struct malidp_hw_device *hwdev, struct videomode *
>  		malidp_hw_setbits(hwdev, MALIDP_DISP_FUNC_ILACED, MALIDP_DE_DISPLAY_FUNC);
>  	else
>  		malidp_hw_clearbits(hwdev, MALIDP_DISP_FUNC_ILACED, MALIDP_DE_DISPLAY_FUNC);
> +
> +	/*
> +	 * Program the RQoS register to avoid 4k resolution flicker
> +	 * on the LS1028A.
> +	 */
> +	if (hwdev->arqos_value) {
> +		val = hwdev->arqos_value;
> +
> +		if (mode->pixelclock == 594000000)

If I remember correctly, you declare the pixelclocks in the device tree, so I
wonder if this is needed here. We should just set what value was in the DT
regardless of the pixelclock, and then you manipulate the DT to choose one of
your fixed resolutions and also set the QoS value.

Best regards,
Liviu

> +			malidp_hw_setbits(hwdev, val, MALIDP500_RQOS_QUALITY);
> +		else
> +			malidp_hw_clearbits(hwdev, val, MALIDP500_RQOS_QUALITY);
> +	}
>  }
>  
>  int malidp_format_get_bpp(u32 fmt)
> diff --git a/drivers/gpu/drm/arm/malidp_hw.h b/drivers/gpu/drm/arm/malidp_hw.h
> index 968a65eed371..e4c36bc90bda 100644
> --- a/drivers/gpu/drm/arm/malidp_hw.h
> +++ b/drivers/gpu/drm/arm/malidp_hw.h
> @@ -251,6 +251,9 @@ struct malidp_hw_device {
>  
>  	/* size of memory used for rotating layers, up to two banks available */
>  	u32 rotation_memory[2];
> +
> +	/* priority level of RQOS register used for driven the ARQOS signal */
> +	u32 arqos_value;
>  };
>  
>  static inline u32 malidp_hw_read(struct malidp_hw_device *hwdev, u32 reg)
> diff --git a/drivers/gpu/drm/arm/malidp_regs.h b/drivers/gpu/drm/arm/malidp_regs.h
> index 993031542fa1..514c50dcb74d 100644
> --- a/drivers/gpu/drm/arm/malidp_regs.h
> +++ b/drivers/gpu/drm/arm/malidp_regs.h
> @@ -210,6 +210,16 @@
>  #define MALIDP500_CONFIG_VALID		0x00f00
>  #define MALIDP500_CONFIG_ID		0x00fd4
>  
> +/*
> + * The quality of service (QoS) register on the DP500. RQOS register values
> + * are driven by the ARQOS signal, using AXI transacations, dependent on the
> + * FIFO input level.
> + * The RQOS register can also set QoS levels for:
> + *    - RED_ARQOS   @ A 4-bit signal value for close to underflow conditions
> + *    - GREEN_ARQOS @ A 4-bit signal value for normal conditions
> + */
> +#define MALIDP500_RQOS_QUALITY          0x00500
> +
>  /* register offsets and bits specific to DP550/DP650 */
>  #define MALIDP550_ADDR_SPACE_SIZE	0x10000
>  #define MALIDP550_DE_CONTROL		0x00010
> -- 
> 2.17.1
> 

-- 
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