[V2,5/5] usb: serial: f81534: fix tx error on some baud rate

[V2,5/5] usb: serial: f81534: fix tx error on some baud rate

[Ji-Ze Hong (Peter Hong)]

The F81532/534 had 4 clocksource 1.846/18.46/14.77/24MHz and baud rates
can be up to 1.5Mbits with 24MHz. But on some baud rate (384~500kps), the
TX side will send the data frame too close to treat frame error on RX
side. This patch will force all TX data frame with delay 1bit gap.

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
---
V2:
	1: First introduced in this series patches.

 drivers/usb/serial/f81534.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/serial/f81534.c b/drivers/usb/serial/f81534.c
index a4666171239a..513805eeae6a 100644
--- a/drivers/usb/serial/f81534.c
+++ b/drivers/usb/serial/f81534.c
@@ -130,6 +130,7 @@
 #define F81534_CLK_18_46_MHZ		(F81534_UART_EN | BIT(1))
 #define F81534_CLK_24_MHZ		(F81534_UART_EN | BIT(2))
 #define F81534_CLK_14_77_MHZ		(F81534_UART_EN | BIT(1) | BIT(2))
+#define F81534_CLK_TX_DELAY_1BIT	BIT(3)
 
 #define F81534_CLK_RS485_MODE		BIT(4)
 #define F81534_CLK_RS485_INVERT		BIT(5)
@@ -1438,6 +1439,11 @@ static int f81534_port_probe(struct usb_serial_port *port)
 		break;
 	}
 
+	/*
+	 * We'll make tx frame error when baud rate from 384~500kps. So we'll
+	 * delay all tx data frame with 1bit.
+	 */
+	port_priv->shadow_clk |= F81534_CLK_TX_DELAY_1BIT;
 	return f81534_set_port_output_pin(port);
 }
 

[V2,5/5] usb: serial: f81534: fix tx error on some baud rate

[Johan Hovold]

On Thu, Jan 04, 2018 at 10:29:21AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> The F81532/534 had 4 clocksource 1.846/18.46/14.77/24MHz and baud rates
> can be up to 1.5Mbits with 24MHz. But on some baud rate (384~500kps), the
> TX side will send the data frame too close to treat frame error on RX
> side. This patch will force all TX data frame with delay 1bit gap.
> 
> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
> ---
> V2:
> 	1: First introduced in this series patches.
> 
>  drivers/usb/serial/f81534.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/serial/f81534.c b/drivers/usb/serial/f81534.c
> index a4666171239a..513805eeae6a 100644
> --- a/drivers/usb/serial/f81534.c
> +++ b/drivers/usb/serial/f81534.c
> @@ -130,6 +130,7 @@
>  #define F81534_CLK_18_46_MHZ		(F81534_UART_EN | BIT(1))
>  #define F81534_CLK_24_MHZ		(F81534_UART_EN | BIT(2))
>  #define F81534_CLK_14_77_MHZ		(F81534_UART_EN | BIT(1) | BIT(2))
> +#define F81534_CLK_TX_DELAY_1BIT	BIT(3)
>  
>  #define F81534_CLK_RS485_MODE		BIT(4)
>  #define F81534_CLK_RS485_INVERT		BIT(5)
> @@ -1438,6 +1439,11 @@ static int f81534_port_probe(struct usb_serial_port *port)
>  		break;
>  	}
>  
> +	/*
> +	 * We'll make tx frame error when baud rate from 384~500kps. So we'll
> +	 * delay all tx data frame with 1bit.
> +	 */
> +	port_priv->shadow_clk |= F81534_CLK_TX_DELAY_1BIT;

You don't wan't to enable this only for the affected rates?

>  	return f81534_set_port_output_pin(port);
>  }

Johan
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[V2,5/5] usb: serial: f81534: fix tx error on some baud rate

[Ji-Ze Hong (Peter Hong)]

Hi Johan,

Johan Hovold 於 2018/1/9 下午 07:32 寫道:
> On Thu, Jan 04, 2018 at 10:29:21AM +0800, Ji-Ze Hong (Peter Hong) wrote:
>> +	/*
>> +	 * We'll make tx frame error when baud rate from 384~500kps. So we'll
>> +	 * delay all tx data frame with 1bit.
>> +	 */
>> +	port_priv->shadow_clk |= F81534_CLK_TX_DELAY_1BIT;
> 
> You don't wan't to enable this only for the affected rates?
> 

This bit will control all transmit TX frame always delay 1 bit
on enabled, but It'll transmit TX frame randomly delay 1 bit on
disabled.

We had tested it with BurnInTest to check the performance,
It'll not make the performance regression. So we'll directly add
it on all baud rate.

Thanks

[V2,5/5] usb: serial: f81534: fix tx error on some baud rate

[Johan Hovold]

On Wed, Jan 10, 2018 at 01:42:32PM +0800, Ji-Ze Hong (Peter Hong) wrote:
> Hi Johan,
> 
> Johan Hovold 於 2018/1/9 下午 07:32 寫道:
> > On Thu, Jan 04, 2018 at 10:29:21AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> >> +	/*
> >> +	 * We'll make tx frame error when baud rate from 384~500kps. So we'll
> >> +	 * delay all tx data frame with 1bit.
> >> +	 */
> >> +	port_priv->shadow_clk |= F81534_CLK_TX_DELAY_1BIT;
> > 
> > You don't wan't to enable this only for the affected rates?
> > 
> 
> This bit will control all transmit TX frame always delay 1 bit
> on enabled, but It'll transmit TX frame randomly delay 1 bit on
> disabled.
> 
> We had tested it with BurnInTest to check the performance,
> It'll not make the performance regression. So we'll directly add
> it on all baud rate.

Ok, thanks for confirming.

Johan
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