Re: [PATCH 2/3] of: Simplify of_dma_set_restricted_buffer() to use of_for_each_phandle()

[Chen-Yu Tsai]

Hi,

On Tue, Mar 18, 2025 at 7:29 AM Rob Herring (Arm) <robh@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
>  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:

simple-pm-bus soc: failed to initialise "restricted-dma-pool" memory node
simple-pm-bus 10006000.syscon: failed to initialise
"restricted-dma-pool" memory node
mtk-tphy soc:t-phy@11c80000: failed to initialise
"restricted-dma-pool" memory node
mtk-tphy soc:t-phy@11ca0000: failed to initialise
"restricted-dma-pool" memory node
mediatek-mipi-tx 11cc0000.dsi-phy: failed to initialise
"restricted-dma-pool" memory node
mediatek-mipi-tx 11cc0000.dsi-phy: can't get nvmem_cell_get, ignore it
clk-mt8186-apmixed 1000c000.syscon: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-topck 10000000.syscon: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-infra-ao 10001000.syscon: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-cam 1a000000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-cam 1a04f000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-cam 1a06f000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-img 15020000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-img 15820000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-imp_iic_wrap 11017000.clock-controller: failed to
initialise "restricted-dma-pool" memory node
clk-mt8186-ipe 1c000000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-mcu c53a000.syscon: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-mdp 1b000000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-mfg 13000000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-vdec 1602f000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-venc 17000000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
clk-mt8186-wpe 14020000.clock-controller: failed to initialise
"restricted-dma-pool" memory node
mt-pmic-pwrap 1000d000.pwrap: failed to initialise
"restricted-dma-pool" memory node
platform 1000d000.pwrap:pmic: failed to initialise
"restricted-dma-pool" memory node
mtk-svs 1100bc00.svs: failed to initialise "restricted-dma-pool" memory node


ChenYu
>  }
>
>  /**
> --
> 2.47.2
>
>