According to CY7C67300 specification HPI read and write cycle duration
Tcyc must be at least 6T long, where T is 1/48MHz, which is 125ns.
Without this delay fast host processor cannot write to chip registers.
Add proper ndelay to hpi_{read,write}_reg.
Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Acked-by: Peter Korsgaard <peter@xxxxxxxxxxxxx>
---
Changes v1 -> v2:
- add HPI_T_CYC_NS macro with a comment why it is needed
drivers/usb/c67x00/c67x00-ll-hpi.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/usb/c67x00/c67x00-ll-hpi.c b/drivers/usb/c67x00/c67x00-ll-hpi.c
index 3a1ca4d..cd2c6ed 100644
--- a/drivers/usb/c67x00/c67x00-ll-hpi.c
+++ b/drivers/usb/c67x00/c67x00-ll-hpi.c
@@ -22,6 +22,7 @@
*/
#include <asm/byteorder.h>
+#include <linux/delay.h>
#include <linux/io.h>
#include <linux/jiffies.h>
#include <linux/usb/c67x00.h>
@@ -73,13 +74,22 @@ struct c67x00_lcp_int_data {
#define HPI_ADDR 2
#define HPI_STATUS 3
+/*
+ * According to CY7C67300 specification (tables 140 and 141) HPI read and
+ * write cycle duration Tcyc must be at least 6T long, where T is 1/48MHz,
+ * which is 125ns.
+ */
+#define HPI_T_CYC_NS 125
+
static inline u16 hpi_read_reg(struct c67x00_device *dev, int reg)
{
+ ndelay(HPI_T_CYC_NS);
return __raw_readw(dev->hpi.base + reg * dev->hpi.regstep);
}
static inline void hpi_write_reg(struct c67x00_device *dev, int reg, u16 value)
{
+ ndelay(HPI_T_CYC_NS);
__raw_writew(value, dev->hpi.base + reg * dev->hpi.regstep);
}
--
1.8.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
