of: restore old handling of cells_name=NULL in of_*_phandle_with_args()

Before commit e42ee61017f5 ("of: Let of_for_each_phandle fallback to
non-negative cell_count") the iterator functions calling
of_for_each_phandle assumed a cell count of 0 if cells_name was NULL.
This corner case was missed when implementing the fallback logic in
e42ee61017f5 and resulted in an endless loop.

Restore the old behaviour of of_count_phandle_with_args() and
of_parse_phandle_with_args() and add a check to
of_phandle_iterator_init() to prevent a similar failure as a safety
precaution. of_parse_phandle_with_args_map() doesn't need a similar fix
as cells_name isn't NULL there.

Affected drivers are:
 - drivers/base/power/domain.c
 - drivers/base/power/domain.c
 - drivers/clk/ti/clk-dra7-atl.c
 - drivers/hwmon/ibmpowernv.c
 - drivers/i2c/muxes/i2c-demux-pinctrl.c
 - drivers/iommu/mtk_iommu.c
 - drivers/net/ethernet/freescale/fman/mac.c
 - drivers/opp/of.c
 - drivers/perf/arm_dsu_pmu.c
 - drivers/regulator/of_regulator.c
 - drivers/remoteproc/imx_rproc.c
 - drivers/soc/rockchip/pm_domains.c
 - sound/soc/fsl/imx-audmix.c
 - sound/soc/fsl/imx-audmix.c
 - sound/soc/meson/axg-card.c
 - sound/soc/samsung/tm2_wm5110.c
 - sound/soc/samsung/tm2_wm5110.c

Thanks to Geert Uytterhoeven for reporting the issue, Peter Rosin for
helping pinpoint the actual problem and the testers for confirming this
fix.

Fixes: e42ee61017f5 ("of: Let of_for_each_phandle fallback to non-negative cell_count")
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Rob Herring <robh@kernel.org>

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 2f25d2dfecfad03d3b9c8ea0ac007f3bd7dc2c13..1d667eb730e197d7de686a074f6194c1036a64b6 100644 (file)
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1286,6 +1286,13 @@ int of_phandle_iterator_init(struct of_phandle_iterator *it,
 
        memset(it, 0, sizeof(*it));
 
+       /*
+        * one of cell_count or cells_name must be provided to determine the
+        * argument length.
+        */
+       if (cell_count < 0 && !cells_name)
+               return -EINVAL;
+
        list = of_get_property(np, list_name, &size);
        if (!list)
                return -ENOENT;
@@ -1512,10 +1519,17 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
                                const char *cells_name, int index,
                                struct of_phandle_args *out_args)
 {
+       int cell_count = -1;
+
        if (index < 0)
                return -EINVAL;
-       return __of_parse_phandle_with_args(np, list_name, cells_name, -1,
-                                           index, out_args);
+
+       /* If cells_name is NULL we assume a cell count of 0 */
+       if (!cells_name)
+               cell_count = 0;
+
+       return __of_parse_phandle_with_args(np, list_name, cells_name,
+                                           cell_count, index, out_args);
 }
 EXPORT_SYMBOL(of_parse_phandle_with_args);
 
@@ -1765,6 +1779,23 @@ int of_count_phandle_with_args(const struct device_node *np, const char *list_na
        struct of_phandle_iterator it;
        int rc, cur_index = 0;
 
+       /*
+        * If cells_name is NULL we assume a cell count of 0. This makes
+        * counting the phandles trivial as each 32bit word in the list is a
+        * phandle and no arguments are to consider. So we don't iterate through
+        * the list but just use the length to determine the phandle count.
+        */
+       if (!cells_name) {
+               const __be32 *list;
+               int size;
+
+               list = of_get_property(np, list_name, &size);
+               if (!list)
+                       return -ENOENT;
+
+               return size / sizeof(*list);
+       }
+
        rc = of_phandle_iterator_init(&it, np, list_name, cells_name, -1);
        if (rc)
                return rc;