RE: [EXT] Re: [v4 2/2] drm/arm/mali-dp: Add display QoS interface configuration for Mali DP500

[Wen He <wen.he_1@nxp.com>]

> -----Original Message-----
> From: Liviu Dudau <liviu.dudau@arm.com>
> Sent: 2019年9月6日 22:18
> To: Wen He <wen.he_1@nxp.com>
> Cc: linux-devel@linux.nxdi.nxp.com; Brian Starkey <brian.starkey@arm.com>;
> David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Rob Herring
> <robh+dt@kernel.org>; Mark Rutland <mark.rutland@arm.com>;
> dri-devel@lists.freedesktop.org; devicetree@vger.kernel.org;
> linux-kernel@vger.kernel.org; Leo Li <leoyang.li@nxp.com>
> Subject: [EXT] Re: [v4 2/2] drm/arm/mali-dp: Add display QoS interface
> configuration for Mali DP500
> 
> Caution: EXT Email
> 
> Hi Wen,
> 
> On Thu, Aug 22, 2019 at 10:11:35AM +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 high resolutions flicker issue on the LS1028A platform.
> >
> > Signed-off-by: Wen He <wen.he_1@nxp.com>
> > ---
> >  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 c27ff456eddc..80e8d15760ac 100644
> > --- a/drivers/gpu/drm/arm/malidp_drv.c
> > +++ b/drivers/gpu/drm/arm/malidp_drv.c
> > @@ -815,6 +815,12 @@ 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;
> > +
> >       /* 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 380be66d4c6e..f90a367a5bc9
> > 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 high resolutions flicker
> > +      * issue on the LS1028A.
> > +      */
> > +     if (hwdev->arqos_value) {
> > +             val = hwdev->arqos_value;
> > +
> > +             if (mode->pixelclock > 148500000)
> > +                     malidp_hw_setbits(hwdev, val,
> MALIDP500_RQOS_QUALITY);
> > +             else
> > +                     malidp_hw_clearbits(hwdev, val,
> MALIDP500_RQOS_QUALITY);
> > +     }
> 
> This application of the arqos_value based on a pixel clock value bothers me,
> because it has two problems:
> 
> 1. Some other user of the Mali DP driver can't apply a system QoS value that
> they can now specify in the DT, unless the requested pixel clock is bigger than
> 145MHz. :(
> 
> 2. (A guess) The flickering issue shows up on a combination of pixelclock and
> resolution (i.e. it is a bandwidth problem), but you only address one of the
> variables. Haven't tested on the LS1028A yet, but do you know if (theoretically)
> it would have a flicker problem doing 640x480@200MHz without the QoS
> value?
> 
> How about this instead?
> 
> --8<---------------------------------------------------------------------
> diff --git a/drivers/gpu/drm/arm/malidp_hw.c
> b/drivers/gpu/drm/arm/malidp_hw.c index 380be66d4c6eb..e2f96dce13850
> 100644
> --- a/drivers/gpu/drm/arm/malidp_hw.c
> +++ b/drivers/gpu/drm/arm/malidp_hw.c
> @@ -374,6 +374,22 @@ 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. LS1028A has an issue where screen
> will
> +        * flicker on pixelclocks higher than 148.5MHz but otherwise doesn't
> +        * want an RQoS value, so special case it for them.
> +        */
> +       if (hwdev->arqos_value) {
> +               val = hwdev->arqos_value;
> +
> +#ifdef MALIDP_LS1028A
> +               if (mode->pixelclock <= 148500000)
> +                       malidp_hw_clearbits(hwdev, val,
> MALIDP500_RQOS_QUALITY);
> +               else
> +#endif
> +                       malidp_hw_setbits(hwdev, val,
> MALIDP500_RQOS_QUALITY);
> +       }
>  }
> 
>  int malidp_format_get_bpp(u32 fmt)
> --8<---------------------------------------------------------------------
> 
> And then you need to define a MALIDP_LS1028A in a vendor patch on top of
> the kernel source code.

That's a good instead, thanks a lot.
After discussed with our team, they think should not put the different on the vendor code, benchmark results
can accept the small reduce, so here should always apply this change.

I will send next version that remove the condition of the pixel clock , thanks a lot.

Best Regards,
Wen

> 
> Best regards,
> Liviu
> 
> 
> >  }
> >
> >  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
> >
> 
> --
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ¯\_(ツ)_/¯