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

[Thomas Zimmermann]

Hi

Am 20.06.25 um 13:07 schrieb Luca Weiss:
> Hi Thomas,
>
> On Fri Jun 20, 2025 at 1:02 PM CEST, Thomas Zimmermann wrote:
> > 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@xxxxxxxxxxxxx>
> > > ---
> > >    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@xxxxxxx>
> Thanks for the reviews!
>
> For both simpledrm.c and simplefb.c, the includes are not strictly
> alphabetically sorted (1 mis-sort in simpledrm, 3 in simplefb), shall I
> just try and slot it into the best fitting place, or make them sorted in
> my patch? Or I can add a separate commit for each driver before to sort
> them.
>
> Let me know!

Best is to try to fit it into the <linux/*> block. In simpledrm, it's 
probably my mistake. Don't bother with sending an extra cleanup if you 
don't want to.

Best regards
Thomas



> Regards
> Luca
>
>
> > 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)