linux-kernel - Re: [PATCH v1 2/2] PCI: j721e: Add support for optional regulator supplies

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Message-ID: <5ogtnqbf32fy4rprcsthip5byl4dtgybsys2ur3ph6mc77q7po@apfcl7olp4zj>
Date: Tue, 28 Oct 2025 11:16:29 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Vitor Soares <ivitro@...il.com>
Cc: Vignesh Raghavendra <vigneshr@...com>, 
	Siddharth Vadapalli <s-vadapalli@...com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, Rob Herring <robh@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Vitor Soares <vitor.soares@...adex.com>, 
	linux-omap@...r.kernel.org, linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] PCI: j721e: Add support for optional regulator
 supplies

On Mon, Oct 27, 2025 at 08:24:12PM +0000, Vitor Soares wrote:
> Hello Mani,
> 
> Thank you for the feedback.
> 
> On Tue, 2025-10-21 at 07:36 +0530, Manivannan Sadhasivam wrote:
> > On Tue, Oct 14, 2025 at 12:25:49PM +0100, Vitor Soares wrote:
> > > From: Vitor Soares <vitor.soares@...adex.com>
> > > 
> > > Some boards require external regulators to power PCIe endpoints.
> > > Add support for optional 1.5V, 3.3V, and 12V supplies, which may be
> > > defined in the device tree as vpcie1v5-supply, vpcie3v3-supply, and
> > > vpcie12v-supply.
> > > 
> > > Use devm_regulator_get_enable_optional() to obtain and enable each
> > > supply, so it will be automatically disabled when the driver is
> > > removed.
> > > 
> > > Signed-off-by: Vitor Soares <vitor.soares@...adex.com>
> > > ---
> > >  drivers/pci/controller/cadence/pci-j721e.c | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > > 
> > > diff --git a/drivers/pci/controller/cadence/pci-j721e.c
> > > b/drivers/pci/controller/cadence/pci-j721e.c
> > > index 5bc5ab20aa6d..f29ce2aef04e 100644
> > > --- a/drivers/pci/controller/cadence/pci-j721e.c
> > > +++ b/drivers/pci/controller/cadence/pci-j721e.c
> > > @@ -21,6 +21,7 @@
> > >  #include <linux/platform_device.h>
> > >  #include <linux/pm_runtime.h>
> > >  #include <linux/regmap.h>
> > > +#include <linux/regulator/consumer.h>
> > >  
> > >  #include "../../pci.h"
> > >  #include "pcie-cadence.h"
> > > @@ -467,6 +468,10 @@ static const struct of_device_id of_j721e_pcie_match[]
> > > = {
> > >  };
> > >  MODULE_DEVICE_TABLE(of, of_j721e_pcie_match);
> > >  
> > > +static const char * const j721e_pcie_supplies[] = {
> > > +       "vpcie12v", "vpcie3v3", "vpcie1v5"
> > > +};
> > 
> > Please don't hardcode the supplies in driver. The DT binding should make sure
> > the relevant supplies are passed (including the optional ones). Just use
> > of_regulator_bulk_get_all() to acquire all the passed supplies.
> > 
> > - Mani
> > 
> 
> I checked the bulk regulator APIs as suggested and of_regulator_bulk_get_all()
> does handle optional supplies correctly, however it is not a managed function
> and doesn't enable the  regulators automatically.
> 
> To use of_regulator_bulk_get_all(), I would need to:
> - Manually enable regulators with regulator_bulk_enable()
> - Add cleanup/disable logic in remove path
> - Handle error cleanup path manually
> 
> This would actually make the code more complex and error-prone compared to the
> current approach using devm_regulator_get_enable_optional(), which provides
> managed cleanup and automatic enable for optional supplies.
> 
> I also checked devm_regulator_bulk_get_enable(), it treats all supplies as
> required and needs the supplies name as well.
> 
> Unless there is a devm_regulator_bulk_get_optional_enable() API I'm not aware
> of, the current per-supply approach is the standard kernel pattern for this use
> case. Would you still prefer the bulk approach despite these limitations?
> 

Fine then. If you do not have a reason to manualy turn off/on the supplies
(during suspend/resume), then it might be better to use
devm_regulator_get_enable_optional() for now.

I'd love to add the managed version of of_regulator_bulk_get_all(), but I guess
Mark wouldn't want it.

- Mani

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