linux-kernel - Re: [PATCH v2 06/14] USB: ch341: reinitialize chip on reconfiguration

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Message-ID: <570A540C.5090706@ladisch.de>
Date:	Sun, 10 Apr 2016 15:24:28 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	Grigori Goronzy <greg@...wn.ath.cx>
Cc:	Johan Hovold <johan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/14] USB: ch341: reinitialize chip on reconfiguration

Grigori Goronzy wrote:
> Changing the LCR register after initialization does not seem to be
> reliable on all chips (particularly not on CH341A).  Restructure
> initialization and configuration to always reinit the chip on
> configuration changes instead and pass the LCR register value directly
> to the initialization command.

> +++ b/drivers/usb/serial/ch341.c
> @@ -155,9 +157,7 @@ static int ch341_set_baudrate(struct usb_device *dev,
>  	a = (factor & 0xff00) | divisor;
>  	b = factor & 0xff;
>
> -	r = ch341_control_out(dev, 0x9a, 0x1312, a);
> -	if (!r)
> -		r = ch341_control_out(dev, 0x9a, 0x0f2c, b);
> +	r = ch341_control_out(dev, CH341_SERIAL_INIT, 0x9c | (ctrl << 8) , a | 0x80);

The variable b is no longer used, so it is no longer necessary to
compute the lower eight bits of the factor.


Regards,
Clemens