linux-kernel - [PATCH v2 1/2] nvmem: qfprom: Ensure access to qfprom is word aligned

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Message-Id: <20241027-sar2130p-nvmem-v2-1-743c1271bf2d@linaro.org>
Date: Sun, 27 Oct 2024 01:42:33 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Naman Jain <quic_namajain@...cinc.com>
Subject: [PATCH v2 1/2] nvmem: qfprom: Ensure access to qfprom is word
 aligned

From: Naman Jain <quic_namajain@...cinc.com>

Add logic for alignment of address for reading in qfprom driver to avoid
NOC error issues due to unaligned access. The problem manifests on the
SAR2130P platform, but in msm-5.x kernels the fix is applied
uncoditionally. Follow this approach and uncoditionally perform aligned
reads.

Fixes: 4ab11996b489 ("nvmem: qfprom: Add Qualcomm QFPROM support.")
Signed-off-by: Naman Jain <quic_namajain@...cinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/nvmem/qfprom.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 116a39e804c70b4a0374f8ea3ac6ba1dd612109d..cad319e7bfcf34c9b9ab15eb331efda822699cce 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -322,15 +322,28 @@ static int qfprom_reg_read(void *context,
 {
 	struct qfprom_priv *priv = context;
 	u8 *val = _val;
-	int i = 0, words = bytes;
+	int buf_start, buf_end, index, i = 0;
 	void __iomem *base = priv->qfpcorrected;
+	char *buffer = NULL;
+	u32 read_val;
 
 	if (read_raw_data && priv->qfpraw)
 		base = priv->qfpraw;
+	buf_start = ALIGN_DOWN(reg, 4);
+	buf_end = ALIGN(reg + bytes, 4);
+	buffer = kzalloc(buf_end - buf_start, GFP_KERNEL);
+	if (!buffer) {
+		pr_err("memory allocation failed in %s\n", __func__);
+		return -ENOMEM;
+	}
 
-	while (words--)
-		*val++ = readb(base + reg + i++);
+	for (index = buf_start; index < buf_end; index += 4, i += 4) {
+		read_val = readl_relaxed(base + index);
+		memcpy(buffer + i, &read_val, 4);
+	}
 
+	memcpy(val, buffer + reg % 4, bytes);
+	kfree(buffer);
 	return 0;
 }
 

-- 
2.39.5