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From: Maxime Ripard <mripard@kernel.org>
Date: Wed, 15 May 2024 15:56:57 +0200
Subject: [PATCH 2/8] of: Add helper to retrieve ECC memory bits
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Message-Id: <20240515-dma-buf-ecc-heap-v1-2-54cbbd049511@kernel.org>
References: <20240515-dma-buf-ecc-heap-v1-0-54cbbd049511@kernel.org>
In-Reply-To: <20240515-dma-buf-ecc-heap-v1-0-54cbbd049511@kernel.org>
To: Rob Herring <robh@kernel.org>, Saravana Kannan <saravanak@google.com>, 
 Sumit Semwal <sumit.semwal@linaro.org>, 
 Benjamin Gaignard <benjamin.gaignard@collabora.com>, 
 Brian Starkey <Brian.Starkey@arm.com>, John Stultz <jstultz@google.com>, 
 "T.J. Mercier" <tjmercier@google.com>, 
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc: Mattijs Korpershoek <mkorpershoek@baylibre.com>, 
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, 
 linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, 
 linaro-mm-sig@lists.linaro.org, Maxime Ripard <mripard@kernel.org>

The /memory device tree bindings allow to store the ECC detection and
correction bits through the ecc-detection-bits and ecc-correction-bits
properties.

Our next patches rely on whether ECC is enabled, so let's add a helper
to retrieve the ECC correction bits from the /memory node.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 include/linux/of.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/of.h b/include/linux/of.h
index a0bedd038a05..2fbee65a7aa9 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -1510,10 +1510,35 @@ static inline int of_get_available_child_count(const struct device_node *np)
 		num++;
 
 	return num;
 }
 
+/**
+ * of_memory_get_ecc_correction_bits() - Returns the number of ECC correction bits
+ *
+ * Search for the number of bits in memory that can be corrected by the
+ * ECC algorithm.
+ *
+ * Returns:
+ * The number of ECC bits, 0 if there's no ECC support, a negative error
+ * code on failure.
+ */
+static inline int of_memory_get_ecc_correction_bits(void)
+{
+	struct device_node *mem;
+	u32 val = 0;
+
+	mem = of_find_node_by_path("/memory");
+	if (!mem)
+		return -ENODEV;
+
+	of_property_read_u32(mem, "ecc-correction-bits", &val);
+	of_node_put(mem);
+
+	return val;
+}
+
 #define _OF_DECLARE_STUB(table, name, compat, fn, fn_type)		\
 	static const struct of_device_id __of_table_##name		\
 		__attribute__((unused))					\
 		 = { .compatible = compat,				\
 		     .data = (fn == (fn_type)NULL) ? fn : fn }

-- 
2.44.0