linux-kernel - [PATCH] i2c: cadence: Fix regression with bus recovery

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Message-Id: <20221125115103.674756-1-carsten.haitzler@foss.arm.com>
Date:   Fri, 25 Nov 2022 11:51:03 +0000
From:   carsten.haitzler@...s.arm.com
To:     michal.simek@...inx.com, shubhrajyoti.datta@...inx.com,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     torvalds@...ux-foundation.org
Subject: [PATCH] i2c: cadence: Fix regression with bus recovery

From: Carsten Haitzler <carsten.haitzler@....com>

Commit "i2c: cadence: Add standard bus recovery support" breaks for i2c
devices that have no pinctrl defined. There is no requirement for this
to exist in the DT. This has worked perfectly well without this before in
at least 1 real usage case on hardware (Mali Komeda DPU, Cadence i2c to
talk to a tda99xx phy). Adding the requirement to have pinctrl set up in
the device tree (or otherwise be found) is a regression where the whole
i2c device is lost entirely (in this case dropping entire devices which
then leads to the drm display stack unable to find the phy for display
output, thus having no drm display device and so on down the chain).

This converts the above commit to an enhancement if pinctrl can be found
for the i2c device, providing a timeout on read with recovery, but if not,
do what used to be done rather than a fatal loss of a device.

This restores the mentioned display devices to their working state again.

Fixes: 58b924241d0a ("i2c: cadence: Add standard bus recovery support")
Signed-off-by: Carsten Haitzler <carsten.haitzler@....com>
---
Note: This issue was discovered during the porting of the linux kernel
on Morello [1].

[1] https://git.morello-project.org/morello/kernel/linux
---
 drivers/i2c/busses/i2c-cadence.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index fe0cd205502d..40d0cc6bb996 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -852,7 +852,8 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 					 CDNS_I2C_POLL_US, CDNS_I2C_TIMEOUT_US);
 	if (ret) {
 		ret = -EAGAIN;
-		i2c_recover_bus(adap);
+		if (id->adap.bus_recovery_info)
+			i2c_recover_bus(adap);
 		goto out;
 	}
 
@@ -1262,10 +1263,10 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 	}
 
 	id->rinfo.pinctrl = devm_pinctrl_get(&pdev->dev);
-	if (IS_ERR(id->rinfo.pinctrl)) {
+	if (IS_ERR(id->rinfo.pinctrl))
 		dev_info(&pdev->dev, "can't get pinctrl, bus recovery not supported\n");
-		return PTR_ERR(id->rinfo.pinctrl);
-	}
+	else
+		id->adap.bus_recovery_info = &id->rinfo;
 
 	id->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r_mem);
 	if (IS_ERR(id->membase))
@@ -1283,7 +1284,6 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 	id->adap.retries = 3;		/* Default retry value. */
 	id->adap.algo_data = id;
 	id->adap.dev.parent = &pdev->dev;
-	id->adap.bus_recovery_info = &id->rinfo;
 	init_completion(&id->xfer_done);
 	snprintf(id->adap.name, sizeof(id->adap.name),
 		 "Cadence I2C at %08lx", (unsigned long)r_mem->start);
-- 
2.32.0