Staging: comedi: convert while loops to timeouts in s626.c

This patch changes a handful of while loops to timeouts to prevent
infinite looping on hardware failure. A couple such loops are in a
function (s626_debi_transfer()) which is called from critical sections,
so comedi_timeout() is unusable for them, and an iterative timeout is
used instead. For the while loops in a context where comedi_timeout() is
allowed, a new callback function, s626_send_dac_eoc(), has been defined
to evaluate the conditions that the while loops are testing.  The new
callback employs a switch statement based on a simple new enum so that
it is usable for all of the different conditions tested in while loops
in s626_send_dac().  The proper comedi_timeout() calls are then used.

Signed-off-by: Chase Southwood <chase.southwood@yahoo.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/s626.c b/drivers/staging/comedi/drivers/s626.c
index 5ba4b4ae6507faa941ed6617ac269343643349e4..fab8ccfa16a9cb8d9ac22f9ee2978612fdfcc992 100644 (file)
--- a/drivers/staging/comedi/drivers/s626.c
+++ b/drivers/staging/comedi/drivers/s626.c
@@ -209,6 +209,8 @@ static const struct comedi_lrange s626_range_table = {
 static void s626_debi_transfer(struct comedi_device *dev)
 {
        struct s626_private *devpriv = dev->private;
+       static const int timeout = 10000;
+       int i;
 
        /* Initiate upload of shadow RAM to DEBI control register */
        s626_mc_enable(dev, S626_MC2_UPLD_DEBI, S626_P_MC2);
@@ -217,12 +219,22 @@ static void s626_debi_transfer(struct comedi_device *dev)
         * Wait for completion of upload from shadow RAM to
         * DEBI control register.
         */
-       while (!s626_mc_test(dev, S626_MC2_UPLD_DEBI, S626_P_MC2))
-               ;
+       for (i = 0; i < timeout; i++) {
+               if (s626_mc_test(dev, S626_MC2_UPLD_DEBI, S626_P_MC2))
+                       break;
+               udelay(1);
+       }
+       if (i == timeout)
+               comedi_error(dev, "Timeout while uploading to DEBI control register.");
 
        /* Wait until DEBI transfer is done */
-       while (readl(devpriv->mmio + S626_P_PSR) & S626_PSR_DEBI_S)
-               ;
+       for (i = 0; i < timeout; i++) {
+               if (!(readl(devpriv->mmio + S626_P_PSR) & S626_PSR_DEBI_S))
+                       break;
+               udelay(1);
+       }
+       if (i == timeout)
+               comedi_error(dev, "DEBI transfer timeout.");
 }
 
 /*
@@ -351,6 +363,48 @@ static const uint8_t s626_trimadrs[] = {
        0x40, 0x41, 0x42, 0x50, 0x51, 0x52, 0x53, 0x60, 0x61, 0x62, 0x63
 };
 
+enum {
+       s626_send_dac_wait_not_mc1_a2out,
+       s626_send_dac_wait_ssr_af2_out,
+       s626_send_dac_wait_fb_buffer2_msb_00,
+       s626_send_dac_wait_fb_buffer2_msb_ff
+};
+
+static int s626_send_dac_eoc(struct comedi_device *dev,
+                            struct comedi_subdevice *s,
+                            struct comedi_insn *insn,
+                            unsigned long context)
+{
+       struct s626_private *devpriv = dev->private;
+       unsigned int status;
+
+       switch (context) {
+       case s626_send_dac_wait_not_mc1_a2out:
+               status = readl(devpriv->mmio + S626_P_MC1);
+               if (!(status & S626_MC1_A2OUT))
+                       return 0;
+               break;
+       case s626_send_dac_wait_ssr_af2_out:
+               status = readl(devpriv->mmio + S626_P_SSR);
+               if (status & S626_SSR_AF2_OUT)
+                       return 0;
+               break;
+       case s626_send_dac_wait_fb_buffer2_msb_00:
+               status = readl(devpriv->mmio + S626_P_FB_BUFFER2);
+               if (!(status & 0xff000000))
+                       return 0;
+               break;
+       case s626_send_dac_wait_fb_buffer2_msb_ff:
+               status = readl(devpriv->mmio + S626_P_FB_BUFFER2);
+               if (status & 0xff000000)
+                       return 0;
+               break;
+       default:
+               return -EINVAL;
+       }
+       return -EBUSY;
+}
+
 /*
  * Private helper function: Transmit serial data to DAC via Audio
  * channel 2.  Assumes: (1) TSL2 slot records initialized, and (2)
@@ -359,6 +413,7 @@ static const uint8_t s626_trimadrs[] = {
 static void s626_send_dac(struct comedi_device *dev, uint32_t val)
 {
        struct s626_private *devpriv = dev->private;
+       int ret;
 
        /* START THE SERIAL CLOCK RUNNING ------------- */
 
@@ -404,8 +459,10 @@ static void s626_send_dac(struct comedi_device *dev, uint32_t val)
         * Done by polling the DMAC enable flag; this flag is automatically
         * cleared when the transfer has finished.
         */
-       while (readl(devpriv->mmio + S626_P_MC1) & S626_MC1_A2OUT)
-               ;
+       ret = comedi_timeout(dev, NULL, NULL, s626_send_dac_eoc,
+                            s626_send_dac_wait_not_mc1_a2out);
+       if (ret)
+               comedi_error(dev, "DMA transfer timeout.");
 
        /* START THE OUTPUT STREAM TO THE TARGET DAC -------------------- */
 
@@ -425,8 +482,10 @@ static void s626_send_dac(struct comedi_device *dev, uint32_t val)
         * finished transferring the DAC's data DWORD from the output FIFO
         * to the output buffer register.
         */
-       while (!(readl(devpriv->mmio + S626_P_SSR) & S626_SSR_AF2_OUT))
-               ;
+       ret = comedi_timeout(dev, NULL, NULL, s626_send_dac_eoc,
+                            s626_send_dac_wait_ssr_af2_out);
+       if (ret)
+               comedi_error(dev, "TSL timeout waiting for slot 1 to execute.");
 
        /*
         * Set up to trap execution at slot 0 when the TSL sequencer cycles
@@ -466,8 +525,10 @@ static void s626_send_dac(struct comedi_device *dev, uint32_t val)
                 * from 0xFF to 0x00, which slot 0 causes to happen by shifting
                 * out/in on SD2 the 0x00 that is always referenced by slot 5.
                 */
-               while (readl(devpriv->mmio + S626_P_FB_BUFFER2) & 0xff000000)
-                       ;
+               ret = comedi_timeout(dev, NULL, NULL, s626_send_dac_eoc,
+                                    s626_send_dac_wait_fb_buffer2_msb_00);
+               if (ret)
+                       comedi_error(dev, "TSL timeout waiting for slot 0 to execute.");
        }
        /*
         * Either (1) we were too late setting the slot 0 trap; the TSL
@@ -486,8 +547,10 @@ static void s626_send_dac(struct comedi_device *dev, uint32_t val)
         * the next DAC write.  This is detected when FB_BUFFER2 MSB changes
         * from 0x00 to 0xFF.
         */
-       while (!(readl(devpriv->mmio + S626_P_FB_BUFFER2) & 0xff000000))
-               ;
+       ret = comedi_timeout(dev, NULL, NULL, s626_send_dac_eoc,
+                            s626_send_dac_wait_fb_buffer2_msb_ff);
+       if (ret)
+               comedi_error(dev, "TSL timeout waiting for slot 0 to execute.");
 }
 
 /*