[svn-commits] dbailey: linux/trunk r7140 - /linux/trunk/drivers/dahdi/wctdm.c

[SVN commits to the Digium repositories]

Author: dbailey
Date: Tue Sep 15 15:50:45 2009
New Revision: 7140

URL: http://svn.asterisk.org/svn-view/dahdi?view=rev&rev=7140
Log:
Change WCTDM SPI clock off state polarity and read timing

Change the off state of the SPI clock to high and provide more time for data to
settle out on SPI reads.

(closes issue #15261)
Reported by: alecdavis
Patches:
      wctdm_spi_clocking.diff2.txt uploaded by alecdavis (license 585)
Tested by: alecdavis, dbailey


Modified:
    linux/trunk/drivers/dahdi/wctdm.c

Modified: linux/trunk/drivers/dahdi/wctdm.c
URL: http://svn.asterisk.org/svn-view/dahdi/linux/trunk/drivers/dahdi/wctdm.c?view=diff&rev=7140&r1=7139&r2=7140
==============================================================================
--- linux/trunk/drivers/dahdi/wctdm.c (original)
+++ linux/trunk/drivers/dahdi/wctdm.c Tue Sep 15 15:50:45 2009
@@ -440,10 +440,14 @@
 
 static inline void __write_8bits(struct wctdm *wc, unsigned char bits)
 {
+/*	Out BIT_CS    --\________________________________/----		*/
+/*	Out BIT_SCLK  ---\_/-\_/-\_/-\_/-\_/-\_/-\_/-\_/------		*/
+/*	Out BIT_SDI   ---\___/---\___/---\___/---\___/--------		*/
+/*	Data Bit            7   6   5   4   3   2   1   0		*/
+/*	Data written        0   1   0   1   0   1   0   1		*/
+
+	int x;
 	/* Drop chip select */
-	int x;
-	wc->ios |= BIT_SCLK;
-	outb(wc->ios, wc->ioaddr + WC_AUXD);
 	wc->ios &= ~BIT_CS;
 	outb(wc->ios, wc->ioaddr + WC_AUXD);
 	for (x=0;x<8;x++) {
@@ -454,6 +458,7 @@
 			wc->ios &= ~BIT_SDI;
 		wc->ios &= ~BIT_SCLK;
 		outb(wc->ios, wc->ioaddr + WC_AUXD);
+
 		/* Now raise SCLK high again and repeat */
 		wc->ios |= BIT_SCLK;
 		outb(wc->ios, wc->ioaddr + WC_AUXD);
@@ -462,7 +467,6 @@
 	/* Finally raise CS back high again */
 	wc->ios |= BIT_CS;
 	outb(wc->ios, wc->ioaddr + WC_AUXD);
-	
 }
 
 static inline void __reset_spi(struct wctdm *wc)
@@ -492,30 +496,35 @@
 
 static inline unsigned char __read_8bits(struct wctdm *wc)
 {
+/*	Out BIT_CS	--\________________________________________/----*/
+/*	Out BIT_SCLK	---\_/--\_/--\_/--\_/--\_/--\_/--\_/--\_/-------*/
+/*	In  BIT_SDO	????/1111\0000/1111\0000/1111\0000/1111\0000/???*/
+/*	Data bit	       7    6    5    4    3    2    1    0	*/
+/*	Data Read	       1    0    1    0    1    0    1    0	*/
+
+/*	Note: Clock High time is 2x Low time, due to input read		*/
+
 	unsigned char res=0, c;
 	int x;
-	wc->ios |= BIT_SCLK;
-	outb(wc->ios, wc->ioaddr + WC_AUXD);
 	/* Drop chip select */
 	wc->ios &= ~BIT_CS;
 	outb(wc->ios, wc->ioaddr + WC_AUXD);
 	for (x=0;x<8;x++) {
 		res <<= 1;
-		/* Get SCLK */
+		/* Drop SCLK */
 		wc->ios &= ~BIT_SCLK;
 		outb(wc->ios, wc->ioaddr + WC_AUXD);
+		/* Now raise SCLK high again */
+		wc->ios |= BIT_SCLK;
+		outb(wc->ios, wc->ioaddr + WC_AUXD);
+
 		/* Read back the value */
 		c = inb(wc->ioaddr + WC_AUXR);
 		if (c & BIT_SDO)
 			res |= 1;
-		/* Now raise SCLK high again */
-		wc->ios |= BIT_SCLK;
-		outb(wc->ios, wc->ioaddr + WC_AUXD);
 	}
 	/* Finally raise CS back high again */
 	wc->ios |= BIT_CS;
-	outb(wc->ios, wc->ioaddr + WC_AUXD);
-	wc->ios &= ~BIT_SCLK;
 	outb(wc->ios, wc->ioaddr + WC_AUXD);
 
 	/* And return our result */