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

[Thomas Zimmermann <tzimmermann@suse.de>]

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@fairphone.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@suse.de>
> 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)