linux-kernel - Re: [PATCH 3/3] fbdev/simplefb: Add support for interconnect paths

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Message-ID: <cf29862b-496b-4825-aa0f-493eb44838a5@suse.de>
Date: Fri, 20 Jun 2025 13:02:14 +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 3/3] fbdev/simplefb: 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/video/fbdev/simplefb.c | 83 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 83 insertions(+)
>
> diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
> index be95fcddce4c8ca794826b805cd7dad2985bd637..ca73e079fd13550ddc779e84db80f7f9b743d074 100644
> --- a/drivers/video/fbdev/simplefb.c
> +++ b/drivers/video/fbdev/simplefb.c
> @@ -27,6 +27,7 @@
>   #include <linux/parser.h>
>   #include <linux/pm_domain.h>
>   #include <linux/regulator/consumer.h>
> +#include <linux/interconnect.h>

With alphabetical sorting:

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

Best regards
Thomas


>   
>   static const struct fb_fix_screeninfo simplefb_fix = {
>   	.id		= "simple",
> @@ -89,6 +90,10 @@ struct simplefb_par {
>   	u32 regulator_count;
>   	struct regulator **regulators;
>   #endif
> +#if defined CONFIG_OF && defined CONFIG_INTERCONNECT
> +	unsigned int icc_count;
> +	struct icc_path **icc_paths;
> +#endif
>   };
>   
>   static void simplefb_clocks_destroy(struct simplefb_par *par);
> @@ -525,6 +530,80 @@ static int simplefb_attach_genpds(struct simplefb_par *par,
>   }
>   #endif
>   
> +#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS
> +/*
> + * Generic interconnect path handling code.
> + */
> +static void simplefb_detach_icc(void *res)
> +{
> +	struct simplefb_par *par = res;
> +	int i;
> +
> +	for (i = par->icc_count - 1; i >= 0; i--) {
> +		if (!IS_ERR_OR_NULL(par->icc_paths[i]))
> +			icc_put(par->icc_paths[i]);
> +	}
> +}
> +
> +static int simplefb_attach_icc(struct simplefb_par *par,
> +			       struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->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) {
> +		dev_err(dev, "invalid interconnects value\n");
> +		return -EINVAL;
> +	}
> +	par->icc_count = count / 2;
> +
> +	par->icc_paths = devm_kcalloc(dev, par->icc_count,
> +				      sizeof(*par->icc_paths),
> +				      GFP_KERNEL);
> +	if (!par->icc_paths)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < par->icc_count; i++) {
> +		par->icc_paths[i] = of_icc_get_by_index(dev, i);
> +		if (IS_ERR_OR_NULL(par->icc_paths[i])) {
> +			ret = PTR_ERR(par->icc_paths[i]);
> +			if (ret == -EPROBE_DEFER)
> +				goto err;
> +			dev_err(dev, "failed to get interconnect path %u: %d\n", i, ret);
> +			continue;
> +		}
> +
> +		ret = icc_set_bw(par->icc_paths[i], 0, UINT_MAX);
> +		if (ret) {
> +			dev_err(dev, "failed to set interconnect bandwidth %u: %d\n", i, ret);
> +			continue;
> +		}
> +	}
> +
> +	return devm_add_action_or_reset(dev, simplefb_detach_icc, par);
> +
> +err:
> +	while (i) {
> +		--i;
> +		if (!IS_ERR_OR_NULL(par->icc_paths[i]))
> +			icc_put(par->icc_paths[i]);
> +	}
> +	return ret;
> +}
> +#else
> +static int simplefb_attach_icc(struct simplefb_par *par,
> +			       struct platform_device *pdev)
> +{
> +	return 0;
> +}
> +#endif
> +
>   static int simplefb_probe(struct platform_device *pdev)
>   {
>   	int ret;
> @@ -615,6 +694,10 @@ static int simplefb_probe(struct platform_device *pdev)
>   	if (ret < 0)
>   		goto error_regulators;
>   
> +	ret = simplefb_attach_icc(par, pdev);
> +	if (ret < 0)
> +		goto error_regulators;
> +
>   	simplefb_clocks_enable(par, pdev);
>   	simplefb_regulators_enable(par, pdev);
>   
>

-- 
--
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)