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SubjectRe: [PATCH v1 1/1] drm/imx/dcss: Add interconnect support
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Am Dienstag, den 01.12.2020, 12:34 +0100 schrieb Guido Günther:
> This allows us to raise DRAM bandiwth to a high enough value for a
> stable picture on i.mx8mq. We pick a bandwidth that should be sufficient
> for 4k@60Hz.
>
> Modelled like mdp5_kms.
>
> Signed-off-by: Guido Günther <agx@sigxcpu.org>
> ---
>  drivers/gpu/drm/imx/dcss/dcss-dev.c | 47 +++++++++++++++++++++++++++--
>  drivers/gpu/drm/imx/dcss/dcss-dev.h | 3 ++
>  2 files changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/imx/dcss/dcss-dev.c b/drivers/gpu/drm/imx/dcss/dcss-dev.c
> index c849533ca83e..e336f03448d6 100644
> --- a/drivers/gpu/drm/imx/dcss/dcss-dev.c
> +++ b/drivers/gpu/drm/imx/dcss/dcss-dev.c
> @@ -15,6 +15,9 @@
>  #include "dcss-dev.h"
>  #include "dcss-kms.h"
>  
> +/* sufficient for 4K at 60 Hz */
> +#define DCSS_BW_MAX GBps_to_icc(2)
> +

Same comment as for the similar change in mxsfb: this should not be a
static value, but should be scaled proportional to the current mode and
plane settings. With a single static value you keep the clocks way too
high for most use-cases with smaller displays, but fail to account for
the additional bandwidth requirement when more than one plane is
active.

Regards,
Lucas

>  static void dcss_clocks_enable(struct dcss_dev *dcss)
>  {
>   clk_prepare_enable(dcss->axi_clk);
> @@ -162,6 +165,31 @@ static void dcss_clks_release(struct dcss_dev *dcss)
>   devm_clk_put(dcss->dev, dcss->apb_clk);
>  }
>  
>
>
>
> +static int dcss_init_icc(struct dcss_dev *dcss)
> +{
> + int ret;
> + struct icc_path *icc_path;
> +
> + /* Optional interconnect request */
> + icc_path = of_icc_get(dcss->dev, NULL);
> + if (IS_ERR(icc_path)) {
> + ret = PTR_ERR(icc_path);
> + if (ret == -EPROBE_DEFER)
> + return ret;
> + /* no interconnect support is not necessarily a fatal
> + * condition, the platform may simply not have an
> + * interconnect driver yet. But warn about it in case
> + * bootloader didn't setup bus clocks high enough for
> + * scanout.
> + */
> + dev_warn(dcss->dev, "No interconnect support may cause display underflows!\n");
> + return 0;
> + }
> + dcss->icc_path = icc_path;
> + dcss->icc_peak_bw = DCSS_BW_MAX;
> + return 0;
> +}
> +
>  struct dcss_dev *dcss_dev_create(struct device *dev, bool hdmi_output)
>  {
>   struct platform_device *pdev = to_platform_device(dev);
> @@ -190,10 +218,14 @@ struct dcss_dev *dcss_dev_create(struct device *dev, bool hdmi_output)
>   dcss->devtype = devtype;
>   dcss->hdmi_output = hdmi_output;
>  
>
>
>
> + ret = dcss_init_icc(dcss);
> + if (ret < 0)
> + goto err;
> +
>   ret = dcss_clks_init(dcss);
>   if (ret) {
>   dev_err(dev, "clocks initialization failed\n");
> - goto err;
> + goto icc_err;
>   }
>  
>
>
>
>   dcss->of_port = of_graph_get_port_by_id(dev->of_node, 0);
> @@ -223,7 +255,8 @@ struct dcss_dev *dcss_dev_create(struct device *dev, bool hdmi_output)
>  
>
>
>
>  clks_err:
>   dcss_clks_release(dcss);
> -
> +icc_err:
> + icc_put(dcss->icc_path);
>  err:
>   kfree(dcss);
>  
>
>
>
> @@ -243,6 +276,8 @@ void dcss_dev_destroy(struct dcss_dev *dcss)
>  
>
>
>
>   dcss_clks_release(dcss);
>  
>
>
>
> + icc_put(dcss->icc_path);
> +
>   kfree(dcss);
>  }
>  
>
>
>
> @@ -267,6 +302,8 @@ int dcss_dev_suspend(struct device *dev)
>  
>
>
>
>   dcss_clocks_disable(dcss);
>  
>
>
>
> + icc_set_bw(dcss->icc_path, 0, 0);
> +
>   return 0;
>  }
>  
>
>
>
> @@ -281,6 +318,8 @@ int dcss_dev_resume(struct device *dev)
>   return 0;
>   }
>  
>
>
>
> + icc_set_bw(dcss->icc_path, 0, dcss->icc_peak_bw);
> +
>   dcss_clocks_enable(dcss);
>  
>
>
>
>   dcss_blkctl_cfg(dcss->blkctl);
> @@ -307,6 +346,8 @@ int dcss_dev_runtime_suspend(struct device *dev)
>  
>
>
>
>   dcss_clocks_disable(dcss);
>  
>
>
>
> + icc_set_bw(dcss->icc_path, 0, 0);
> +
>   return 0;
>  }
>  
>
>
>
> @@ -314,6 +355,8 @@ int dcss_dev_runtime_resume(struct device *dev)
>  {
>   struct dcss_dev *dcss = dcss_drv_dev_to_dcss(dev);
>  
>
>
>
> + icc_set_bw(dcss->icc_path, 0, dcss->icc_peak_bw);
> +
>   dcss_clocks_enable(dcss);
>  
>
>
>
>   dcss_blkctl_cfg(dcss->blkctl);
> diff --git a/drivers/gpu/drm/imx/dcss/dcss-dev.h b/drivers/gpu/drm/imx/dcss/dcss-dev.h
> index c642ae17837f..1b35a6f0d0d4 100644
> --- a/drivers/gpu/drm/imx/dcss/dcss-dev.h
> +++ b/drivers/gpu/drm/imx/dcss/dcss-dev.h
> @@ -8,6 +8,7 @@
>  
>
>
>
>  #include <drm/drm_fourcc.h>
>  #include <linux/io.h>
> +#include <linux/interconnect.h>
>  #include <video/videomode.h>
>  
>
>
>
>  #define SET 0x04
> @@ -85,6 +86,8 @@ struct dcss_dev {
>   struct clk *pll_phy_ref_clk;
>  
>
>
>
>   bool hdmi_output;
> + struct icc_path *icc_path;
> + u32 icc_peak_bw;
>  
>
>
>
>   void (*disable_callback)(void *data);
>   struct completion disable_completion;


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