[PATCH] mmc: pxamci: Fix passing NULL to PTR_ERR() in pxamci_probe()

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

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

Case 1:
When dma_request_chan() fails, host->dma_chan_rx is an ERR_PTR(),
but it is reset to NULL before using PTR_ERR(), resulting in PTR_ERR(0).
This mistakenly returns 0 instead of the real error code.

Case 2:
When devm_clk_get() fails, host->clk is an ERR_PTR() resulting in the similar
issue like case 1. 

Store the error code before nullifying the pointers in both the cases.

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")
Signed-off-by: Rakuram Eswaran <rakuram.e96@gmail.com>
---

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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c
index 26d03352af63..4fab693d3b32 100644
--- a/drivers/mmc/host/pxamci.c
+++ b/drivers/mmc/host/pxamci.c
@@ -653,8 +653,9 @@ static int pxamci_probe(struct platform_device *pdev)
 
 	host->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(host->clk)) {
+		ret = PTR_ERR(host->clk);
 		host->clk = NULL;
-		return PTR_ERR(host->clk);
+		return ret;
 	}
 
 	host->clkrate = clk_get_rate(host->clk);
@@ -705,8 +706,9 @@ static int pxamci_probe(struct platform_device *pdev)
 
 	host->dma_chan_rx = dma_request_chan(dev, "rx");
 	if (IS_ERR(host->dma_chan_rx)) {
+		ret = PTR_ERR(host->dma_chan_rx);
 		host->dma_chan_rx = NULL;
-		return dev_err_probe(dev, PTR_ERR(host->dma_chan_rx),
+		return dev_err_probe(dev, ret,
 				     "unable to request rx dma channel\n");
 	}
 
-- 
2.48.1