mvtwsi: Fix clock programming

The TWSI_FREQUENCY macro was wrong in 2 ways: 1) It was casting the result of the calculations to an u8, while i2c clk rates are often >= 100Khz which won't fit in a u8, drop the cast. 2) It had an extra factor of 2 in the divider which neither the datasheet nor the Linux driver have. The comment for the default value was wrongly saying that m lives in bits 4-7, while in reality it is in bits 3-6, as can be seen from the correct shift by 3 used in i2c_init(). While at it remove the unused twsi_actual_speed variable. Signed-off-by: Hans de Goede <hdegoede@redhat.com>

mvtwsi: Fix clock programming
The TWSI_FREQUENCY macro was wrong in 2 ways: 1) It was casting the result of the calculations to an u8, while i2c clk rates are often >= 100Khz which won't fit in a u8, drop the cast. 2) It had an extra factor of 2 in the divider which neither the datasheet nor the Linux driver have. The comment for the default value was wrongly saying that m lives in bits 4-7, while in reality it is in bits 3-6, as can be seen from the correct shift by 3 used in i2c_init(). While at it remove the unused twsi_actual_speed variable. Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Hans de Goede · Heiko Schocher
1 parent 557a331908
Showing 1 changed file with 2 additions and 5 deletions Side-by-side Diff
drivers/i2c/mvtwsi.c
@@ -216,7 +216,7 @@
  */
  
 #define TWSI_FREQUENCY(m, n) \
-	((u8) (CONFIG_SYS_TCLK / (10 * (m + 1) * 2 * (1 << n))))
+	(CONFIG_SYS_TCLK / (10 * (m + 1) * (1 << n)))
  
 /*
  * These are required to be reprogrammed before enabling the controller
  
@@ -225,10 +225,8 @@
  * twsi_slave_address left uninitialized lest checkpatch.pl complains.
  */
  
-/* Baudrate generator: m (bits 7..4) =4, n (bits 3..0) =4 */
+/* Baudrate generator: m (bits 6..3) = 8, n (bits 2..0) = 4 */
 static u8 twsi_baud_rate = 0x44; /* baudrate at controller reset */
-/* Default frequency corresponding to default m=4, n=4 */
-static u8 twsi_actual_speed = TWSI_FREQUENCY(4, 4);
 /* Default slave address is 0 (so is an uninitialized static) */
 static u8 twsi_slave_address;
  
@@ -279,7 +277,6 @@
 	}
 	/* save baud rate and slave for later calls to twsi_reset */
 	twsi_baud_rate = baud;
-	twsi_actual_speed = highest_speed;
 	twsi_slave_address = slaveadd;
 	/* reset controller */
 	twsi_reset();
...	...	@@ -216,7 +216,7 @@
216	216	*/
217	217
218	218	#define TWSI_FREQUENCY(m, n) \
219		- ((u8) (CONFIG_SYS_TCLK / (10 * (m + 1) * 2 * (1 << n))))
	219	+ (CONFIG_SYS_TCLK / (10 * (m + 1) * (1 << n)))
220	220
221	221	/*
222	222	* These are required to be reprogrammed before enabling the controller
223	223
...	...	@@ -225,10 +225,8 @@
225	225	* twsi_slave_address left uninitialized lest checkpatch.pl complains.
226	226	*/
227	227
228		-/* Baudrate generator: m (bits 7..4) =4, n (bits 3..0) =4 */
	228	+/* Baudrate generator: m (bits 6..3) = 8, n (bits 2..0) = 4 */
229	229	static u8 twsi_baud_rate = 0x44; /* baudrate at controller reset */
230		-/* Default frequency corresponding to default m=4, n=4 */
231		-static u8 twsi_actual_speed = TWSI_FREQUENCY(4, 4);
232	230	/* Default slave address is 0 (so is an uninitialized static) */
233	231	static u8 twsi_slave_address;
234	232
...	...	@@ -279,7 +277,6 @@
279	277	}
280	278	/* save baud rate and slave for later calls to twsi_reset */
281	279	twsi_baud_rate = baud;
282		- twsi_actual_speed = highest_speed;
283	280	twsi_slave_address = slaveadd;
284	281	/* reset controller */
285	282	twsi_reset();