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* [PATCH] tty: serial: samsung: Correct clock selection logic
@ 2020-05-09  1:34 ` Jonathan Bakker
  0 siblings, 0 replies; 6+ messages in thread
From: Jonathan Bakker @ 2020-05-09  1:34 UTC (permalink / raw)
  To: kgene, krzk, gregkh, jslaby, linux-arm-kernel, linux-samsung-soc,
	linux-serial, linux-kernel
  Cc: Jonathan Bakker

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>
---
 drivers/tty/serial/samsung_tty.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 73f951d65b93..9d2b4be44209 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1281,14 +1281,14 @@ 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);
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH] tty: serial: samsung: Correct clock selection logic
@ 2020-05-09  1:34 ` Jonathan Bakker
  0 siblings, 0 replies; 6+ messages in thread
From: Jonathan Bakker @ 2020-05-09  1:34 UTC (permalink / raw)
  To: kgene, krzk, gregkh, jslaby, linux-arm-kernel, linux-samsung-soc,
	linux-serial, linux-kernel
  Cc: Jonathan Bakker

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>
---
 drivers/tty/serial/samsung_tty.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 73f951d65b93..9d2b4be44209 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1281,14 +1281,14 @@ 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);
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH] tty: serial: samsung: Correct clock selection logic
  2020-05-09  1:34 ` Jonathan Bakker
@ 2020-05-11 10:08   ` Krzysztof Kozlowski
  -1 siblings, 0 replies; 6+ messages in thread
From: Krzysztof Kozlowski @ 2020-05-11 10:08 UTC (permalink / raw)
  To: Jonathan Bakker
  Cc: kgene, gregkh, jslaby, linux-arm-kernel, linux-samsung-soc,
	linux-serial, linux-kernel

On Fri, May 08, 2020 at 06:34:33PM -0700, Jonathan Bakker wrote:
> 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>
> ---
>  drivers/tty/serial/samsung_tty.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index 73f951d65b93..9d2b4be44209 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -1281,14 +1281,14 @@ 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 */

Makes sense and good catch.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

I wonder about the s3c24xx_serial_enable_baudclk() which has similar
pattern - is there
testing only def_clk_sel on purpose?

Best regards,
Krzysztof

> +		if (ourport->cfg->clk_sel &&
> +			!(ourport->cfg->clk_sel & (1 << cnt)))
>  			continue;
>  
>  		sprintf(clkname, "clk_uart_baud%d", cnt);
> -- 
> 2.20.1
> 

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] tty: serial: samsung: Correct clock selection logic
@ 2020-05-11 10:08   ` Krzysztof Kozlowski
  0 siblings, 0 replies; 6+ messages in thread
From: Krzysztof Kozlowski @ 2020-05-11 10:08 UTC (permalink / raw)
  To: Jonathan Bakker
  Cc: linux-samsung-soc, gregkh, linux-kernel, kgene, linux-serial,
	jslaby, linux-arm-kernel

On Fri, May 08, 2020 at 06:34:33PM -0700, Jonathan Bakker wrote:
> 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>
> ---
>  drivers/tty/serial/samsung_tty.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index 73f951d65b93..9d2b4be44209 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -1281,14 +1281,14 @@ 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 */

Makes sense and good catch.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

I wonder about the s3c24xx_serial_enable_baudclk() which has similar
pattern - is there
testing only def_clk_sel on purpose?

Best regards,
Krzysztof

> +		if (ourport->cfg->clk_sel &&
> +			!(ourport->cfg->clk_sel & (1 << cnt)))
>  			continue;
>  
>  		sprintf(clkname, "clk_uart_baud%d", cnt);
> -- 
> 2.20.1
> 

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] tty: serial: samsung: Correct clock selection logic
  2020-05-11 10:08   ` Krzysztof Kozlowski
@ 2020-05-11 19:40     ` Jonathan Bakker
  -1 siblings, 0 replies; 6+ messages in thread
From: Jonathan Bakker @ 2020-05-11 19:40 UTC (permalink / raw)
  To: Krzysztof Kozlowski
  Cc: kgene, gregkh, jslaby, linux-arm-kernel, linux-samsung-soc,
	linux-serial, linux-kernel

Hi Krzysztof,

On 2020-05-11 3:08 a.m., Krzysztof Kozlowski wrote:
> On Fri, May 08, 2020 at 06:34:33PM -0700, Jonathan Bakker wrote:
>> 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>
>> ---
>>  drivers/tty/serial/samsung_tty.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
>> index 73f951d65b93..9d2b4be44209 100644
>> --- a/drivers/tty/serial/samsung_tty.c
>> +++ b/drivers/tty/serial/samsung_tty.c
>> @@ -1281,14 +1281,14 @@ 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 */
> 
> Makes sense and good catch.
> 
> Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
> 
> I wonder about the s3c24xx_serial_enable_baudclk() which has similar
> pattern - is there
> testing only def_clk_sel on purpose?

Yeah, I saw this instance too.  5086e0a409a0c ("tty: serial: samsung: Enable
baud clock during initialisation") introduced it, which was just to make sure
that some clock was enabled during initialization.  Since it doesn't appear to
be critical which clock it is, I left it as it was.

Thanks,
Jonathan

> 
> Best regards,
> Krzysztof
> 
>> +		if (ourport->cfg->clk_sel &&
>> +			!(ourport->cfg->clk_sel & (1 << cnt)))
>>  			continue;
>>  
>>  		sprintf(clkname, "clk_uart_baud%d", cnt);
>> -- 
>> 2.20.1
>>

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] tty: serial: samsung: Correct clock selection logic
@ 2020-05-11 19:40     ` Jonathan Bakker
  0 siblings, 0 replies; 6+ messages in thread
From: Jonathan Bakker @ 2020-05-11 19:40 UTC (permalink / raw)
  To: Krzysztof Kozlowski
  Cc: linux-samsung-soc, gregkh, linux-kernel, kgene, linux-serial,
	jslaby, linux-arm-kernel

Hi Krzysztof,

On 2020-05-11 3:08 a.m., Krzysztof Kozlowski wrote:
> On Fri, May 08, 2020 at 06:34:33PM -0700, Jonathan Bakker wrote:
>> 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>
>> ---
>>  drivers/tty/serial/samsung_tty.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
>> index 73f951d65b93..9d2b4be44209 100644
>> --- a/drivers/tty/serial/samsung_tty.c
>> +++ b/drivers/tty/serial/samsung_tty.c
>> @@ -1281,14 +1281,14 @@ 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 */
> 
> Makes sense and good catch.
> 
> Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
> 
> I wonder about the s3c24xx_serial_enable_baudclk() which has similar
> pattern - is there
> testing only def_clk_sel on purpose?

Yeah, I saw this instance too.  5086e0a409a0c ("tty: serial: samsung: Enable
baud clock during initialisation") introduced it, which was just to make sure
that some clock was enabled during initialization.  Since it doesn't appear to
be critical which clock it is, I left it as it was.

Thanks,
Jonathan

> 
> Best regards,
> Krzysztof
> 
>> +		if (ourport->cfg->clk_sel &&
>> +			!(ourport->cfg->clk_sel & (1 << cnt)))
>>  			continue;
>>  
>>  		sprintf(clkname, "clk_uart_baud%d", cnt);
>> -- 
>> 2.20.1
>>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-05-11 19:54 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-09  1:34 [PATCH] tty: serial: samsung: Correct clock selection logic Jonathan Bakker
2020-05-09  1:34 ` Jonathan Bakker
2020-05-11 10:08 ` Krzysztof Kozlowski
2020-05-11 10:08   ` Krzysztof Kozlowski
2020-05-11 19:40   ` Jonathan Bakker
2020-05-11 19:40     ` Jonathan Bakker

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