linux-kernel - [PATCH v2 1/4] media: ov08x40: Fix burst write sequence

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Message-Id: <20241001-b4-master-24-11-25-ov08x40-v2-1-e478976b20c1@linaro.org>
Date: Tue, 01 Oct 2024 14:15:49 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Jason Chen <jason.z.chen@...el.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>, 
 Hans Verkuil <hverkuil-cisco@...all.nl>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 devicetree@...r.kernel.org, Bryan O'Donoghue <bryan.odonoghue@...aro.org>, 
 stable@...r.kernel.org
Subject: [PATCH v2 1/4] media: ov08x40: Fix burst write sequence

It is necessary to account for I2C quirks in the burst mode path of this
driver. Not all I2C controllers can accept arbitrarily long writes and this
is represented in the quirks field of the adapter structure.

Prior to this patch the following error message is seen on a Qualcomm
X1E80100 CRD.

[   38.773524] i2c i2c-2: adapter quirk: msg too long (addr 0x0036, size 290, write)
[   38.781454] ov08x40 2-0036: Failed regs transferred: -95
[   38.787076] ov08x40 2-0036: ov08x40_start_streaming failed to set regs

Fix the error by breaking up the write sequence into the advertised maximum
write size of the quirks field if the quirks field is populated.

Fixes: 8f667d202384 ("media: ov08x40: Reduce start streaming time")
Cc: stable@...r.kernel.org # v6.9+
Tested-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org> # x1e80100-crd
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
---
 drivers/media/i2c/ov08x40.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/media/i2c/ov08x40.c b/drivers/media/i2c/ov08x40.c
index 48df077522ad0bb2b5f64a6def8844c02af6a193..be25e45175b1322145dca428e845242d8fea2698 100644
--- a/drivers/media/i2c/ov08x40.c
+++ b/drivers/media/i2c/ov08x40.c
@@ -1339,15 +1339,13 @@ static int ov08x40_read_reg(struct ov08x40 *ov08x,
 	return 0;
 }
 
-static int ov08x40_burst_fill_regs(struct ov08x40 *ov08x, u16 first_reg,
-				   u16 last_reg,  u8 val)
+static int __ov08x40_burst_fill_regs(struct i2c_client *client, u16 first_reg,
+				     u16 last_reg, size_t num_regs, u8 val)
 {
-	struct i2c_client *client = v4l2_get_subdevdata(&ov08x->sd);
 	struct i2c_msg msgs;
-	size_t i, num_regs;
+	size_t i;
 	int ret;
 
-	num_regs = last_reg - first_reg + 1;
 	msgs.addr = client->addr;
 	msgs.flags = 0;
 	msgs.len = 2 + num_regs;
@@ -1373,6 +1371,31 @@ static int ov08x40_burst_fill_regs(struct ov08x40 *ov08x, u16 first_reg,
 	return 0;
 }
 
+static int ov08x40_burst_fill_regs(struct ov08x40 *ov08x, u16 first_reg,
+				   u16 last_reg,  u8 val)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(&ov08x->sd);
+	size_t num_regs, num_write_regs;
+	int ret;
+
+	num_regs = last_reg - first_reg + 1;
+	num_write_regs = num_regs;
+
+	if (client->adapter->quirks && client->adapter->quirks->max_write_len)
+		num_write_regs = client->adapter->quirks->max_write_len - 2;
+
+	while (first_reg < last_reg) {
+		ret = __ov08x40_burst_fill_regs(client, first_reg, last_reg,
+						num_write_regs, val);
+		if (ret)
+			return ret;
+
+		first_reg += num_write_regs;
+	}
+
+	return 0;
+}
+
 /* Write registers up to 4 at a time */
 static int ov08x40_write_reg(struct ov08x40 *ov08x,
 			     u16 reg, u32 len, u32 __val)

-- 
2.46.2