From ae60961b5f0f15914c2eff950f22b6afb594f88c Mon Sep 17 00:00:00 2001
From: jflecool2 <1393416+jflecool2@users.noreply.github.com>
Date: Thu, 5 Nov 2026 16:11:06 -0800
Subject: [PATCH] i2c: designware: Fix SDA hold default being computed before
 LCNT

The "SDA hold time = LCNT / 2" default added by commit "i2c: designware:
Make the SDA hold time half LCNT" (see raspberrypi/linux#6091) is applied
in i2c_dw_probe(), before i2c_dw_probe_master() has run
i2c_dw_set_timings_master() to populate dev->fs_lcnt. fs_lcnt is therefore
still 0, the default evaluates to 0, and i2c_dw_set_sda_hold() keeps the
hardware reset value (1 cycle, ~5 ns) instead of the intended ~3 us.

On a Pi 5 (200 MHz clk_sys, 100 kHz bus) this leaves IC_SDA_HOLD at 0x10001
rather than 0x10251 as on 6.18, and reintroduces the early-ACK failures that
#6091 and #6056 fixed: an Adafruit PiOLED (SSD1306, 0x3c) fails with
"SDA stuck at low" / "Remote I/O error" on 7.3.1 while it works on 6.18.

Do the lcnt/2 default and i2c_dw_set_sda_hold() after i2c_dw_probe_master(),
so fs_lcnt is valid. i2c_dw_init(), which writes the register, still runs
afterwards.

Tested on a Pi 5 running 7.3.1: IC_SDA_HOLD reads 0x10251 and the OLED
works.

Assisted-by: GitHub Copilot CLI:claude-sonnet-5.5
Signed-off-by: jflecool2 <1393416+jflecool2@users.noreply.github.com>
---
 drivers/i2c/busses/i2c-designware-common.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
index a4efb891da9fac..2eb5cba21ffb45 100644
--- a/drivers/i2c/busses/i2c-designware-common.c
+++ b/drivers/i2c/busses/i2c-designware-common.c
@@ -949,18 +949,18 @@ int i2c_dw_probe(struct dw_i2c_dev *dev)
 	if (ret)
 		return ret;
 
-	if (!dev->sda_hold_time)
-		dev->sda_hold_time = dev->fs_lcnt / 2;
-
-	ret = i2c_dw_set_sda_hold(dev);
+	ret = i2c_dw_set_fifo_size(dev);
 	if (ret)
 		return ret;
 
-	ret = i2c_dw_set_fifo_size(dev);
+	ret = i2c_dw_probe_master(dev);
 	if (ret)
 		return ret;
 
-	ret = i2c_dw_probe_master(dev);
+	if (!dev->sda_hold_time)
+		dev->sda_hold_time = dev->fs_lcnt / 2;
+
+	ret = i2c_dw_set_sda_hold(dev);
 	if (ret)
 		return ret;