[PATCH AUTOSEL 4.14 100/127] tty: serial: samsung: Correct clock selection logic

Sasha Levin
2020-09-18T02:31:35Z

From: Jonathan Bakker <xc-racer2@live.ca>

[ Upstream commit 7d31676a8d91dd18e08853efd1cb26961a38c6a6 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/samsung.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index c67d39fea74ca..70d29b697e822 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1165,14 +1165,14 @@ 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);
--
2.25.1