[PATCH v2] mmc: pxamci: Simplify pxamci_probe() error handling using devm APIs

[Rakuram Eswaran <rakuram.e96@gmail.com>]

This patch refactors pxamci_probe() to use devm-managed resource
allocation (e.g. devm_dma_request_chan()) and dev_err_probe() for
improved readability and automatic cleanup on probe failure.

This eliminates redundant NULL assignments and manual release logic.

This issue was originally reported by Smatch:
drivers/mmc/host/pxamci.c:709 pxamci_probe() warn: passing zero to 'PTR_ERR'

The warning occurred because a pointer was set to NULL before using
PTR_ERR(), leading to PTR_ERR(0) and an incorrect 0 return value.
This refactor eliminates that condition while improving overall
error handling robustness.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202510041841.pRlunIfl-lkp@intel.com/
Fixes: 58c40f3faf742c ("mmc: pxamci: Use devm_mmc_alloc_host() helper")
Suggested-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Signed-off-by: Rakuram Eswaran <rakuram.e96@gmail.com>
---

Changes since v1:
Following Uwe Kleine-König’s suggestion:
- Replaced dma_request_chan() with devm_dma_request_chan() to make DMA
  channel allocation devm-managed and avoid manual release paths.
- Used dev_err_probe() for improved error reporting and consistent
  probe failure handling.
- Removed redundant NULL assignments and obsolete goto-based cleanup logic.
- Updated commit message to better describe the intent of the change.

Testing note:
I do not have access to appropriate hardware for runtime testing. 
Any help verifying on actual hardware would be appreciated.

Build and Analysis:
This patch was compiled against the configuration file reported by
0day CI in the above link (config: s390-randconfig-r071-20251004) using
`s390x-linux-gnu-gcc (Ubuntu 14.2.0-19ubuntu2) 14.2.0`. 

Static analysis was performed with Smatch to ensure the reported warning 
no longer reproduces after applying this fix.

Command used for verification:
  ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- \
  ~/project/smatch/smatch_scripts/kchecker ./drivers/mmc/host/pxamci.c

 drivers/mmc/host/pxamci.c | 57 +++++++++++++++------------------------
 1 file changed, 21 insertions(+), 36 deletions(-)

diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c
index 26d03352af63..d03388f64934 100644
--- a/drivers/mmc/host/pxamci.c
+++ b/drivers/mmc/host/pxamci.c
@@ -652,11 +652,14 @@ static int pxamci_probe(struct platform_device *pdev)
 	host->clkrt = CLKRT_OFF;
 
 	host->clk = devm_clk_get(dev, NULL);
-	if (IS_ERR(host->clk)) {
-		host->clk = NULL;
-		return PTR_ERR(host->clk);
-	}
+	if (IS_ERR(host->clk))
+		return dev_err_probe(dev, PTR_ERR(host->clk),
+				     "Failed to acquire clock\n");
 
+	/*
+	 * Note that the return value of clk_get_rate() is only valid
+	 * if the clock is enabled.
+	 */
 	host->clkrate = clk_get_rate(host->clk);
 
 	/*
@@ -703,46 +706,36 @@ static int pxamci_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, mmc);
 
-	host->dma_chan_rx = dma_request_chan(dev, "rx");
-	if (IS_ERR(host->dma_chan_rx)) {
-		host->dma_chan_rx = NULL;
+	host->dma_chan_rx = devm_dma_request_chan(dev, "rx");
+	if (IS_ERR(host->dma_chan_rx))
 		return dev_err_probe(dev, PTR_ERR(host->dma_chan_rx),
 				     "unable to request rx dma channel\n");
-	}
 
-	host->dma_chan_tx = dma_request_chan(dev, "tx");
-	if (IS_ERR(host->dma_chan_tx)) {
-		dev_err(dev, "unable to request tx dma channel\n");
-		ret = PTR_ERR(host->dma_chan_tx);
-		host->dma_chan_tx = NULL;
-		goto out;
-	}
+	host->dma_chan_tx = devm_dma_request_chan(dev, "tx");
+	if (IS_ERR(host->dma_chan_tx))
+		return dev_err_probe(dev, PTR_ERR(host->dma_chan_tx),
+				     "unable to request tx dma channel\n");
 
 	if (host->pdata) {
 		host->detect_delay_ms = host->pdata->detect_delay_ms;
 
 		host->power = devm_gpiod_get_optional(dev, "power", GPIOD_OUT_LOW);
-		if (IS_ERR(host->power)) {
-			ret = PTR_ERR(host->power);
-			dev_err(dev, "Failed requesting gpio_power\n");
-			goto out;
-		}
+		if (IS_ERR(host->power))
+			return dev_err_probe(dev, PTR_ERR(host->power),
+						"Failed requesting gpio_power\n");
 
 		/* FIXME: should we pass detection delay to debounce? */
 		ret = mmc_gpiod_request_cd(mmc, "cd", 0, false, 0);
-		if (ret && ret != -ENOENT) {
-			dev_err(dev, "Failed requesting gpio_cd\n");
-			goto out;
-		}
+		if (ret && ret != -ENOENT)
+			return dev_err_probe(dev, ret, "Failed requesting gpio_cd\n");
 
 		if (!host->pdata->gpio_card_ro_invert)
 			mmc->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
 
 		ret = mmc_gpiod_request_ro(mmc, "wp", 0, 0);
-		if (ret && ret != -ENOENT) {
-			dev_err(dev, "Failed requesting gpio_ro\n");
-			goto out;
-		}
+		if (ret && ret != -ENOENT)
+			return dev_err_probe(dev, ret, "Failed requesting gpio_ro\n");
+
 		if (!ret)
 			host->use_ro_gpio = true;
 
@@ -759,16 +752,8 @@ static int pxamci_probe(struct platform_device *pdev)
 	if (ret) {
 		if (host->pdata && host->pdata->exit)
 			host->pdata->exit(dev, mmc);
-		goto out;
 	}
 
-	return 0;
-
-out:
-	if (host->dma_chan_rx)
-		dma_release_channel(host->dma_chan_rx);
-	if (host->dma_chan_tx)
-		dma_release_channel(host->dma_chan_tx);
 	return ret;
 }
 
-- 
2.48.1