Messages in this thread | | | Subject | Re: [PATCH v10 4/8] drm/ingenic: Add dw-hdmi driver for jz4780 | From | "H. Nikolaus Schaller" <> | Date | Wed, 1 Dec 2021 15:33:24 +0100 |
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Hi Paul,
> Am 01.12.2021 um 15:03 schrieb Paul Cercueil <paul@crapouillou.net>: > > Hi Nikolaus, Mark, > > Le mer., déc. 1 2021 at 14:51:51 +0100, H. Nikolaus Schaller <hns@goldelico.com> a écrit : >> Hi, >>> Am 01.12.2021 um 14:39 schrieb Mark Brown <broonie@kernel.org>: >>> On Wed, Dec 01, 2021 at 01:02:45PM +0000, Paul Cercueil wrote: >>>> Le mar., nov. 30 2021 at 22:26:37 +0100, H. Nikolaus Schaller >>>>> + regulator = devm_regulator_get_optional(&pdev->dev, "hdmi-5v"); >>>>> + if (IS_ERR(regulator)) { >>>>> + ret = PTR_ERR(regulator); >>> Why is this using _optional()? This should only be done when the supply >>> can be physically absent >> There can be +5V for HDMI but without a regulator that is visible to or controllable >> by the driver. > > There is always a power supply though. Either a controllable one (through e.g. a GPIO), or it's just connected to the mains +5V; the pin is never left floating. In the second case, in DTS the "hdmi-5v" would be connected to some 5v regulator, even if it's just a dummy VCC-5V regulator. So Mark has a point. > >> So hdmi-5v can be simply missing in DTS in which case the driver does not need to >> care about. The driver just can't turn it on or off. > > Please make it mandatory in DTS then, and use devm_regulator_get() in the driver.
Well, I just wonder why the elegant devm_regulator_get_optional() exists at all and seems to be used in ca. 80 places.
And if it is not allowed, why some DTS should be forced to add not physically existing dummy-regulators. AFAIR drivers should implement functionality defined by DTS but not the other way round: enforce DTS style. BTW: there is no +5 mains dummy regulator defined in ci20.dts.
What I fear is that if we always have to define the mains +5V (which is for example not defined in ci20.dts), which rules stops us from asking to add a dummy-regulator from 110/230V to +5V as well. In last consequence, it seems as if we have to describe all dummy regulators from the power plant to our hdmi-5v :)
Since I always follow the KISS principle I tend to leave out what is not relevant...
Of course adding a dummy regulator to the DTS allows to avoid the NULL pointer test in the driver code.
Anyways, you are maintainers :)
So should I spin a v11 for the series or just this patch or how should we do it?
BR and thanks, Nikolaus
> > Cheers, > -Paul > >>> (in which case I'd expect to see special >>> handling). >> The special case is to not enable/disable the regulator if it does not exist >> and assume that there is hardware providing it otherwise (the driver can't know >> that except by using get_optional). This is done by the code below >>>>> + if (IS_ERR(regulator)) { >> ... >>> + if (!regulator) >>> + return 0; >>> + ret = regulator_enable(regulator); >> ... >> BR and thanks, >> Nikolaus > >
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