On 9/6/2022 11:38 AM, SCHNEIDER Johannes wrote:
Hi Peng Fan,
... well i'm actually not sure why the messages get corrupted; it's just what i
observed on a connected oscilloscope :-s
the code that does uses the transmit functions is making use of the returned
-EAGAIN and retries - and even strewing in some delays to wait for the buffer
or checking the status register didn't resolve the issue -- switching the
serical driver from locking onto the single send-register to actually checking
the fifo fixed it though.
i can put these "vague reasons" in the commit message... but i dont/didn't
think theyd help much (?)
That's fine, I just wanna know more details. Maybe add one line
"followling linux kernel i.MX8M* uart driver, check UTS_TXFULL, not
UTS_EMPTY."
Regards,
Peng.
regards
________________________________
From: Peng Fan <[email protected]>
Sent: Tuesday, September 6, 2022 02:54
To: SCHNEIDER Johannes <[email protected]>;
[email protected] <[email protected]>
Cc: trini <[email protected]>; GEO-CHHER-bsp-development
<[email protected]>; [email protected] <[email protected]>; [email protected]
<[email protected]>; Pali Rohár <[email protected]>
Subject: Re: [PATCH v2 2/2] serial: mxc: have putc use the TXFIFO
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On 9/5/2022 5:58 PM, Johannes Schneider wrote:
only waiting for TXEMPTY leads to corrupted messages going over the
wire - which is fixed by making use of the FIFO
Could you please explain a bit more, why waiting TXEMPTY could lead
to corrupted message?
Thanks,
Peng.
Signed-off-by: Johannes Schneider <[email protected]>
---
(no changes since v1)
drivers/serial/serial_mxc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
index 5f283cc635..1e0add7281 100644
--- a/drivers/serial/serial_mxc.c
+++ b/drivers/serial/serial_mxc.c
@@ -309,7 +309,7 @@ static int mxc_serial_putc(struct udevice *dev, const char
ch)
struct mxc_serial_plat *plat = dev_get_plat(dev);
struct mxc_uart *const uart = plat->reg;
- if (!(readl(&uart->ts) & UTS_TXEMPTY))
+ if (readl(&uart->ts) & UTS_TXFULL)
return -EAGAIN;
writel(ch, &uart->txd);
