[PATCH] mmc: tmio_mmc_dma: don't print invalid DMA cookie

The tmio_mmc_start_dma_{rx,tx} function functions contain debug
code that prints the dma cookie among other things. However,
in case we fall back to PIO mode for some reason, the cookie
variable is never initialized, and gcc warns about this:

In file included from ../include/linux/printk.h:277:0,
                 from ../include/linux/kernel.h:13,
                 from ../include/linux/list.h:8,
                 from ../include/linux/kobject.h:20,
                 from ../include/linux/device.h:17,
                 from ../drivers/mmc/host/tmio_mmc_dma.c:13:
../drivers/mmc/host/tmio_mmc_dma.c: In function 'tmio_mmc_start_dma':
../include/linux/dynamic_debug.h:86:3: warning: 'cookie' may be used uninitialized in this function [-Wmaybe-uninitialized]
   __dynamic_dev_dbg(&descriptor, dev, fmt, \
   ^
../drivers/mmc/host/tmio_mmc_dma.c:128:15: note: 'cookie' was declared here
  dma_cookie_t cookie;

This modifies the dev_dbg() statements so we only print the cookie
when we are already in the DMA path.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
This warning has existed for a long time, and it's only in debug code,
so probably nobody cared.

diff --git a/drivers/mmc/host/tmio_mmc_dma.c b/drivers/mmc/host/tmio_mmc_dma.c
index e4b05dbb9ca8..4a0d6b80eaa3 100644
--- a/drivers/mmc/host/tmio_mmc_dma.c
+++ b/drivers/mmc/host/tmio_mmc_dma.c

@@ -94,9 +94,9 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
 			desc = NULL;
 			ret = cookie;
 		}
+		dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
+			__func__, host->sg_len, ret, cookie, host->mrq);
 	}
-	dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
-		__func__, host->sg_len, ret, cookie, host->mrq);
 
 pio:
 	if (!desc) {

@@ -116,8 +116,8 @@ pio:
 			 "DMA failed: %d, falling back to PIO\n", ret);
 	}
 
-	dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d, sg[%d]\n", __func__,
-		desc, cookie, host->sg_len);
+	dev_dbg(&host->pdev->dev, "%s(): desc %p, sg[%d]\n", __func__,
+		desc, host->sg_len);
 }
 
 static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)

@@ -174,9 +174,9 @@ static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
 			desc = NULL;
 			ret = cookie;
 		}
+		dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
+			__func__, host->sg_len, ret, cookie, host->mrq);
 	}
-	dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
-		__func__, host->sg_len, ret, cookie, host->mrq);
 
 pio:
 	if (!desc) {

@@ -196,8 +196,7 @@ pio:
 			 "DMA failed: %d, falling back to PIO\n", ret);
 	}
 
-	dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d\n", __func__,
-		desc, cookie);
+	dev_dbg(&host->pdev->dev, "%s(): desc %p\n", __func__, desc);
 }
 
 void tmio_mmc_start_dma(struct tmio_mmc_host *host,

On 13 January 2016 at 22:25, Arnd Bergmann [off-list ref] wrote:

The tmio_mmc_start_dma_{rx,tx} function functions contain debug
code that prints the dma cookie among other things. However,
in case we fall back to PIO mode for some reason, the cookie
variable is never initialized, and gcc warns about this:

In file included from ../include/linux/printk.h:277:0,
                 from ../include/linux/kernel.h:13,
                 from ../include/linux/list.h:8,
                 from ../include/linux/kobject.h:20,
                 from ../include/linux/device.h:17,
                 from ../drivers/mmc/host/tmio_mmc_dma.c:13:
../drivers/mmc/host/tmio_mmc_dma.c: In function 'tmio_mmc_start_dma':
../include/linux/dynamic_debug.h:86:3: warning: 'cookie' may be used uninitialized in this function [-Wmaybe-uninitialized]
   __dynamic_dev_dbg(&descriptor, dev, fmt, \
   ^
../drivers/mmc/host/tmio_mmc_dma.c:128:15: note: 'cookie' was declared here
  dma_cookie_t cookie;

This modifies the dev_dbg() statements so we only print the cookie
when we are already in the DMA path.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks, applied for fixes!

Kind regards
Uffe