From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:41230 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753695AbeBBRR3 (ORCPT ); Fri, 2 Feb 2018 12:17:29 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ed Blake , Heikki Krogerus , Lukas Wunner , Andy Shevchenko Subject: [PATCH 4.15 47/55] serial: 8250_dw: Revert "Improve clock rate setting" Date: Fri, 2 Feb 2018 17:59:05 +0100 Message-Id: <20180202140830.649634918@linuxfoundation.org> In-Reply-To: <20180202140826.117602411@linuxfoundation.org> References: <20180202140826.117602411@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Shevchenko commit c14b65feac9ebed649d6fe79c6b6d64d21d0287d upstream. The commit de9e33bdfa22 ("serial: 8250_dw: Improve clock rate setting") obviously tries to cure symptoms, and not a root cause. The root cause is the non-flexible rate calculation inside the corresponding clock driver. What we need is to provide maximum UART divisor value to the clock driver to allow it do the job transparently to the caller. Since from the initial commit message I have got no clue which clock driver actually needs to be amended, I leave this exercise to the people who know better the case. Moreover, it seems [1] the fix introduced a regression. And possible even one more [2]. Taking above, revert the commit de9e33bdfa22 for now. [1]: https://www.spinics.net/lists/linux-serial/msg28872.html [2]: https://github.com/Dunedan/mbp-2016-linux/issues/29#issuecomment-357583782 Fixes: de9e33bdfa22 ("serial: 8250_dw: Improve clock rate setting") Cc: Ed Blake Cc: Heikki Krogerus Cc: Lukas Wunner Signed-off-by: Andy Shevchenko Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dw.c | 30 ++++++++++++------------------ 1 file changed, 12 insertions(+), 18 deletions(-) --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -252,31 +252,25 @@ static void dw8250_set_termios(struct ua struct ktermios *old) { unsigned int baud = tty_termios_baud_rate(termios); - unsigned int target_rate, min_rate, max_rate; struct dw8250_data *d = p->private_data; long rate; - int i, ret; + int ret; if (IS_ERR(d->clk) || !old) goto out; - /* Find a clk rate within +/-1.6% of an integer multiple of baudx16 */ - target_rate = baud * 16; - min_rate = target_rate - (target_rate >> 6); - max_rate = target_rate + (target_rate >> 6); - - for (i = 1; i <= UART_DIV_MAX; i++) { - rate = clk_round_rate(d->clk, i * target_rate); - if (rate >= i * min_rate && rate <= i * max_rate) - break; - } - if (i <= UART_DIV_MAX) { - clk_disable_unprepare(d->clk); + clk_disable_unprepare(d->clk); + rate = clk_round_rate(d->clk, baud * 16); + if (rate < 0) + ret = rate; + else if (rate == 0) + ret = -ENOENT; + else ret = clk_set_rate(d->clk, rate); - clk_prepare_enable(d->clk); - if (!ret) - p->uartclk = rate; - } + clk_prepare_enable(d->clk); + + if (!ret) + p->uartclk = rate; out: p->status &= ~UPSTAT_AUTOCTS;