linux-kernel - [PATCH v3 4/5] nvmem: qfprom: switch to 4-byte aligned reads

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Message-Id: <20250104-sar2130p-nvmem-v3-4-a94e0b7de2fa@linaro.org>
Date: Sat, 04 Jan 2025 08:19:15 +0200
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: Akhil P Oommen <quic_akhilpo@...cinc.com>, 
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/5] nvmem: qfprom: switch to 4-byte aligned reads

All platforms since Snapdragon 8 Gen1 (SM8450) require using 4-byte
reads to access QFPROM data. While older platforms were more than happy
with 1-byte reads, change the qfprom driver to use 4-byte reads for all
the platforms. Specify stride and word size of 4 bytes. To retain
compatibility with the existing DT and to simplify porting data from
vendor kernels, use fixup_dt_cell_info in order to bump alignment
requirements.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/nvmem/qfprom.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 116a39e804c70b4a0374f8ea3ac6ba1dd612109d..a872c640b8c5a558da9ea00e3804c904f8987247 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -321,19 +321,32 @@ static int qfprom_reg_read(void *context,
 			unsigned int reg, void *_val, size_t bytes)
 {
 	struct qfprom_priv *priv = context;
-	u8 *val = _val;
-	int i = 0, words = bytes;
+	u32 *val = _val;
 	void __iomem *base = priv->qfpcorrected;
+	int words = DIV_ROUND_UP(bytes, sizeof(u32));
+	int i;
 
 	if (read_raw_data && priv->qfpraw)
 		base = priv->qfpraw;
 
-	while (words--)
-		*val++ = readb(base + reg + i++);
+	for (i = 0; i < words; i++)
+		*val++ = readl(base + reg + i * sizeof(u32));
 
 	return 0;
 }
 
+/* Align reads to word boundary */
+static void qfprom_fixup_dt_cell_info(struct nvmem_device *nvmem,
+				      struct nvmem_cell_info *cell)
+{
+	unsigned int byte_offset = cell->offset % sizeof(u32);
+
+	cell->bit_offset += byte_offset * BITS_PER_BYTE;
+	cell->offset -= byte_offset;
+	if (byte_offset && !cell->nbits)
+		cell->nbits = cell->bytes * BITS_PER_BYTE;
+}
+
 static void qfprom_runtime_disable(void *data)
 {
 	pm_runtime_disable(data);
@@ -358,10 +371,11 @@ static int qfprom_probe(struct platform_device *pdev)
 	struct nvmem_config econfig = {
 		.name = "qfprom",
 		.add_legacy_fixed_of_cells = true,
-		.stride = 1,
-		.word_size = 1,
+		.stride = 4,
+		.word_size = 4,
 		.id = NVMEM_DEVID_AUTO,
 		.reg_read = qfprom_reg_read,
+		.fixup_dt_cell_info = qfprom_fixup_dt_cell_info,
 	};
 	struct device *dev = &pdev->dev;
 	struct resource *res;

-- 
2.39.5