linux-kernel - Re: [PATCH 2/3] drm/sysfb: simpledrm: Add support for interconnect paths

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Message-ID: <95f59f54-0f7b-4268-8811-ccc4af565368@suse.de>
Date: Fri, 20 Jun 2025 13:01:22 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Luca Weiss <luca.weiss@...rphone.com>, Hans de Goede
 <hdegoede@...hat.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Javier Martinez Canillas <javierm@...hat.com>, Helge Deller <deller@....de>
Cc: linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] drm/sysfb: simpledrm: Add support for interconnect
 paths

Hi

Am 20.06.25 um 12:31 schrieb Luca Weiss:
> Some devices might require keeping an interconnect path alive so that
> the framebuffer continues working. Add support for that by setting the
> bandwidth requirements appropriately for all provided interconnect
> paths.
>
> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> ---
>   drivers/gpu/drm/sysfb/simpledrm.c | 83 +++++++++++++++++++++++++++++++++++++++
>   1 file changed, 83 insertions(+)
>
> diff --git a/drivers/gpu/drm/sysfb/simpledrm.c b/drivers/gpu/drm/sysfb/simpledrm.c
> index a1c3119330deffc9e122b83941f3697e5b87f277..9643f7c1734ab558d52779d7c45465dbe1d85762 100644
> --- a/drivers/gpu/drm/sysfb/simpledrm.c
> +++ b/drivers/gpu/drm/sysfb/simpledrm.c
> @@ -9,6 +9,7 @@
>   #include <linux/platform_device.h>
>   #include <linux/pm_domain.h>
>   #include <linux/regulator/consumer.h>
> +#include <linux/interconnect.h>

Alphabetical sorting please.

Apart from this nitpick, the patch looks good. For the update:

Reviewed-by: Thomas Zimmermann <tzimmermann>

Best regards
Thomas

>   
>   #include <drm/clients/drm_client_setup.h>
>   #include <drm/drm_atomic.h>
> @@ -225,6 +226,10 @@ struct simpledrm_device {
>   	struct device **pwr_dom_devs;
>   	struct device_link **pwr_dom_links;
>   #endif
> +#if defined CONFIG_OF && defined CONFIG_INTERCONNECT
> +	unsigned int icc_count;
> +	struct icc_path **icc_paths;
> +#endif
>   
>   	/* modesetting */
>   	u32 formats[DRM_SYSFB_PLANE_NFORMATS(1)];
> @@ -547,6 +552,81 @@ static int simpledrm_device_attach_genpd(struct simpledrm_device *sdev)
>   }
>   #endif
>   
> +#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS
> +/*
> + * Generic interconnect path handling code.
> + */
> +static void simpledrm_device_detach_icc(void *res)
> +{
> +	struct simpledrm_device *sdev = res;
> +	int i;
> +
> +	for (i = sdev->icc_count - 1; i >= 0; i--) {
> +		if (!IS_ERR_OR_NULL(sdev->icc_paths[i]))
> +			icc_put(sdev->icc_paths[i]);
> +	}
> +}
> +
> +static int simpledrm_device_attach_icc(struct simpledrm_device *sdev)
> +{
> +	struct device *dev = sdev->sysfb.dev.dev;
> +	int ret, count, i;
> +
> +	count = of_count_phandle_with_args(dev->of_node, "interconnects",
> +							 "#interconnect-cells");
> +	if (count < 0)
> +		return 0;
> +
> +	/* An interconnect path consists of two elements */
> +	if (count % 2) {
> +		drm_err(&sdev->sysfb.dev,
> +			"invalid interconnects value\n");
> +		return -EINVAL;
> +	}
> +	sdev->icc_count = count / 2;
> +
> +	sdev->icc_paths = devm_kcalloc(dev, sdev->icc_count,
> +					       sizeof(*sdev->icc_paths),
> +					       GFP_KERNEL);
> +	if (!sdev->icc_paths)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < sdev->icc_count; i++) {
> +		sdev->icc_paths[i] = of_icc_get_by_index(dev, i);
> +		if (IS_ERR_OR_NULL(sdev->icc_paths[i])) {
> +			ret = PTR_ERR(sdev->icc_paths[i]);
> +			if (ret == -EPROBE_DEFER)
> +				goto err;
> +			drm_err(&sdev->sysfb.dev, "failed to get interconnect path %u: %d\n",
> +				i, ret);
> +			continue;
> +		}
> +
> +		ret = icc_set_bw(sdev->icc_paths[i], 0, UINT_MAX);
> +		if (ret) {
> +			drm_err(&sdev->sysfb.dev, "failed to set interconnect bandwidth %u: %d\n",
> +				i, ret);
> +			continue;
> +		}
> +	}
> +
> +	return devm_add_action_or_reset(dev, simpledrm_device_detach_icc, sdev);
> +
> +err:
> +	while (i) {
> +		--i;
> +		if (!IS_ERR_OR_NULL(sdev->icc_paths[i]))
> +			icc_put(sdev->icc_paths[i]);
> +	}
> +	return ret;
> +}
> +#else
> +static int simpledrm_device_attach_icc(struct simpledrm_device *sdev)
> +{
> +	return 0;
> +}
> +#endif
> +
>   /*
>    * Modesetting
>    */
> @@ -633,6 +713,9 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
>   	if (ret)
>   		return ERR_PTR(ret);
>   	ret = simpledrm_device_attach_genpd(sdev);
> +	if (ret)
> +		return ERR_PTR(ret);
> +	ret = simpledrm_device_attach_icc(sdev);
>   	if (ret)
>   		return ERR_PTR(ret);
>   
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)