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 (?)
regards ________________________________ From: Peng Fan peng.fan@oss.nxp.com Sent: Tuesday, September 6, 2022 02:54 To: SCHNEIDER Johannes johannes.schneider@leica-geosystems.com; u-boot@lists.denx.de u-boot@lists.denx.de Cc: trini trini@konsulko.com; GEO-CHHER-bsp-development bsp-development.geo@leica-geosystems.com; festevam@denx.de festevam@denx.de; sbabic@denx.de sbabic@denx.de; Pali Rohár pali@kernel.org 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 johannes.schneider@leica-geosystems.com
(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);