The minimum baud rate was hardcoded, not computed from first principles.
The break condition simulation added in a later patch will also need to
make use of the minimum baud rate.
The (1 + ((x - 1) / y)) pattern is to force rounding up (mathematically
the minimum rate is about 45.78bps).
Signed-off-by: Michael Hanselmann <public@xxxxxxxxx>
---
Rebase on top of usb-next and wording change in commit message.
drivers/usb/serial/ch341.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 97214e1ec5d2..202cfa4ef6c7 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -147,6 +147,8 @@ static int ch341_control_in(struct usb_device *dev,
#define CH341_CLKRATE 48000000
#define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
+#define CH341_MIN_BPS \
+ (unsigned int)(1 + (((CH341_CLKRATE) - 1) / (CH341_CLK_DIV(0, 0) * 256)))
#define CH341_MIN_RATE(ps) (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
static const speed_t ch341_min_rates[] = {
@@ -174,10 +176,10 @@ static int ch341_get_divisor(struct ch341_private *priv)
int ps;
/*
- * Clamp to supported range, this makes the (ps < 0) and (div < 2)
- * sanity checks below redundant.
+ * Clamp to supported range, making the later range sanity checks
+ * redundant.
*/
- speed = clamp(speed, 46U, 3000000U);
+ speed = clamp(speed, CH341_MIN_BPS, 3000000U);
/*
* Start with highest possible base clock (fact = 1) that will give a
--
2.20.1
