Commit 7d31676a authored May 08, 2020 by Jonathan Bakker Committed by Greg Kroah-Hartman May 15, 2020

tty: serial: samsung: Correct clock selection logic

Some variants of the samsung tty driver can pick which clock
to use for their baud rate generation. In the DT conversion,
a default clock was selected to be used if a specific one wasn't
assigned and then a comparison of which clock rate worked better
was done. Unfortunately, the comparison was implemented in such
a way that only the default clock was ever actually compared.
Fix this by iterating through all possible clocks, except when a
specific clock has already been picked via clk_sel (which is
only possible via board files).

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/BN6PR04MB06604E63833EA41837EBF77BA3A30@BN6PR04MB0660.namprd04.prod.outlook.com

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ad406341

drivers/tty/serial/samsung_tty.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -1304,14 +1304,14 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
		struct s3c24xx_uart_info *info = ourport->info;
		struct clk *clk;
		unsigned long rate;
		unsigned int cnt, baud, quot, clk_sel, best_quot = 0;
		unsigned int cnt, baud, quot, best_quot = 0;
		char clkname[MAX_CLK_NAME_LENGTH];
		int calc_deviation, deviation = (1 << 30) - 1;

		clk_sel = (ourport->cfg->clk_sel) ? ourport->cfg->clk_sel :
		ourport->info->def_clk_sel;
		for (cnt = 0; cnt < info->num_clks; cnt++) {
		if (!(clk_sel & (1 << cnt)))
		/* Keep selected clock if provided */
		if (ourport->cfg->clk_sel &&
		!(ourport->cfg->clk_sel & (1 << cnt)))
		continue;

		sprintf(clkname, "clk_uart_baud%d", cnt);