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authorAndy Shevchenko <andriy.shevchenko@linux.intel.com>2018-01-19 18:02:05 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-22 14:13:40 +0100
commitc14b65feac9ebed649d6fe79c6b6d64d21d0287d (patch)
treef3c8e24ec266f46b2b7d85c28e19c584514319d5
parenta0075d168a19dab5e015a03ffafbd6ab8e7d0c04 (diff)
serial: 8250_dw: Revert "Improve clock rate setting"
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: stable <stable@vger.kernel.org> # 4.15 Cc: Ed Blake <ed.blake@sondrel.com> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com> Cc: Lukas Wunner <lukas@wunner.de> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/8250/8250_dw.c30
1 files changed, 12 insertions, 18 deletions
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index bda75d317d24..cd1b94a0f451 100644
--- 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 uart_port *p, struct ktermios *termios,
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;