linux-kernel - Re: [PATCH 2/3] of: Simplify of_dma_set_restricted_buffer() to use of_for_each

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Message-ID: <CAL_JsqLoJAwPeWjXyQYK1rvVzn6Meapz3iS9gW+QqYpYKuJkBQ@mail.gmail.com>
Date: Wed, 26 Mar 2025 13:52:49 -0500
From: Rob Herring <robh@...nel.org>
To: wens@...nel.org
Cc: Saravana Kannan <saravanak@...gle.com>, Bjorn Andersson <andersson@...nel.org>, 
	Mathieu Poirier <mathieu.poirier@...aro.org>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, Patrice Chotard <patrice.chotard@...s.st.com>, 
	Maxime Coquelin <mcoquelin.stm32@...il.com>, Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-remoteproc@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 2/3] of: Simplify of_dma_set_restricted_buffer() to use of_for_each_phandle()

On Wed, Mar 26, 2025 at 1:44 AM Chen-Yu Tsai <wens@...nel.org> wrote:
>
> Hi,
>
> On Tue, Mar 18, 2025 at 7:29 AM Rob Herring (Arm) <robh@...nel.org> wrote:
> >
> > Simplify of_dma_set_restricted_buffer() by using of_property_present()
> > and of_for_each_phandle() iterator.
> >
> > Signed-off-by: Rob Herring (Arm) <robh@...nel.org>
> > ---
> >  drivers/of/device.c | 34 +++++++++++++---------------------
> >  1 file changed, 13 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/of/device.c b/drivers/of/device.c
> > index edf3be197265..bb4a47d58249 100644
> > --- a/drivers/of/device.c
> > +++ b/drivers/of/device.c
> > @@ -35,44 +35,36 @@ EXPORT_SYMBOL(of_match_device);
> >  static void
> >  of_dma_set_restricted_buffer(struct device *dev, struct device_node *np)
> >  {
> > -       struct device_node *node, *of_node = dev->of_node;
> > -       int count, i;
> > +       struct device_node *of_node = dev->of_node;
> > +       struct of_phandle_iterator it;
> > +       int rc, i = 0;
> >
> >         if (!IS_ENABLED(CONFIG_DMA_RESTRICTED_POOL))
> >                 return;
> >
> > -       count = of_property_count_elems_of_size(of_node, "memory-region",
> > -                                               sizeof(u32));
> >         /*
> >          * If dev->of_node doesn't exist or doesn't contain memory-region, try
> >          * the OF node having DMA configuration.
> >          */
> > -       if (count <= 0) {
> > +       if (!of_property_present(of_node, "memory-region"))
> >                 of_node = np;
> > -               count = of_property_count_elems_of_size(
> > -                       of_node, "memory-region", sizeof(u32));
> > -       }
> >
> > -       for (i = 0; i < count; i++) {
> > -               node = of_parse_phandle(of_node, "memory-region", i);
> > +       of_for_each_phandle(&it, rc, of_node, "memory-region", NULL, 0) {
> >                 /*
> >                  * There might be multiple memory regions, but only one
> >                  * restricted-dma-pool region is allowed.
> >                  */
> > -               if (of_device_is_compatible(node, "restricted-dma-pool") &&
> > -                   of_device_is_available(node)) {
> > -                       of_node_put(node);
> > -                       break;
> > +               if (of_device_is_compatible(it.node, "restricted-dma-pool") &&
> > +                   of_device_is_available(it.node)) {
> > +                       if (!of_reserved_mem_device_init_by_idx(dev, of_node, i)) {
> > +                               of_node_put(it.node);
> > +                               return;
> > +                       }
> >                 }
> > -               of_node_put(node);
> > +               i++;
> >         }
> >
> > -       /*
> > -        * Attempt to initialize a restricted-dma-pool region if one was found.
> > -        * Note that count can hold a negative error code.
> > -        */
> > -       if (i < count && of_reserved_mem_device_init_by_idx(dev, of_node, i))
> > -               dev_warn(dev, "failed to initialise \"restricted-dma-pool\" memory node\n");
> > +       dev_warn(dev, "failed to initialise \"restricted-dma-pool\" memory node\n");
>
> This changes the behavior. Before this patch, it was:
>
>     if a restricted dma pool was found, but initializing it failed, print
>     a warning.
>
> Whereas now it has become:
>
>      print a warning unless a restricted dma pool was found and successfully
>      initialized.
>
> This change causes the kernel to print out the warning for devices that
> don't even do DMA:

Thanks. I fixed it up to only warn if i is non-zero.

Rob