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[0/2] tty: serial: samsung: Serial fixes for Apple A7-A11 SoCs

Message ID 20240907111431.2970-1-towinchenmi@gmail.com
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Series tty: serial: samsung: Serial fixes for Apple A7-A11 SoCs | expand

Message

Nick Chan Sept. 7, 2024, 11:06 a.m. UTC 
Hi,

This series fixes issues with serial on A7-A11 SoCs. The changes do not
seem to affect existing M1 and up users so they can be applied
unconditionally.

Firstly, these SoCs require 32-bit writes on the serial port. This only
manifested in earlycon as reg-io-width in device tree is consulted for
normal serial writes.

Secondly, A7-A9 SoCs seems to use different bits for RXTO and RXTO
enable. Accessing these bits in addition to the original RXTO and RXTO
enable bits will allow serial rx to work correctly on those SoCs.

Nick Chan

---

Nick Chan (2):
  tty: serial: samsung: Fix A7-A11 serial earlycon SError
  tty: serial: samsung: Fix serial rx on Apple A7-A9

 drivers/tty/serial/samsung_tty.c | 23 ++++++++++++++++-------
 include/linux/serial_s3c.h       | 18 +++++++++++-------
 2 files changed, 27 insertions(+), 14 deletions(-)


base-commit: 9aaeb87ce1e966169a57f53a02ba05b30880ffb8

Comments

Krzysztof Kozlowski Sept. 7, 2024, 12:54 p.m. UTC | #1 
On 07/09/2024 13:06, Nick Chan wrote:
> Apple's earlier SoCs, like A7-A11, requires 32-bit writes for the serial
> port. Otherwise, a SError happens when writing to UTXH (+0x20). This only
> manifested in earlycon as reg-io-width in the device tree is consulted
> for normal serial writes.
> 
> Change the iotype of the port to UPIO_MEM32, to allow the serial port to
> function on A7-A11 SoCs. This change does not appear to affect Apple M1 and
> above.
> 
> Signed-off-by: Nick Chan <towinchenmi@gmail.com>
> ---
>  drivers/tty/serial/samsung_tty.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index c4f2ac9518aa..27b8a50bd3e7 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -2536,7 +2536,7 @@ static const struct s3c24xx_serial_drv_data s5l_serial_drv_data = {
>  		.name		= "Apple S5L UART",
>  		.type		= TYPE_APPLE_S5L,
>  		.port_type	= PORT_8250,
> -		.iotype		= UPIO_MEM,
> +		.iotype		= UPIO_MEM32,
>  		.fifosize	= 16,
>  		.rx_fifomask	= S3C2410_UFSTAT_RXMASK,
>  		.rx_fifoshift	= S3C2410_UFSTAT_RXSHIFT,
> @@ -2825,8 +2825,10 @@ static int __init apple_s5l_early_console_setup(struct earlycon_device *device,
>  	/* Close enough to S3C2410 for earlycon... */
>  	device->port.private_data = &s3c2410_early_console_data;
>  
> +	/* ... however, we need to change the port iotype */
> +	device->port.iotype = UPIO_MEM32;

If there is going to be resend, then this comment is redundant and can
be dropped - repeats the code and does not provide any explanation why.

Which would also make the patch smaller and easier to read. See GS101
earlycon.



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

Best regards,
Krzysztof
Nick Chan Sept. 7, 2024, 1:22 p.m. UTC | #2 
On 7/9/2024 20:54, Krzysztof Kozlowski wrote:
> On 07/09/2024 13:06, Nick Chan wrote:
>> Apple's earlier SoCs, like A7-A11, requires 32-bit writes for the serial
>> port. Otherwise, a SError happens when writing to UTXH (+0x20). This only
>> manifested in earlycon as reg-io-width in the device tree is consulted
>> for normal serial writes.
>>
>> Change the iotype of the port to UPIO_MEM32, to allow the serial port to
>> function on A7-A11 SoCs. This change does not appear to affect Apple M1 and
>> above.
>>
>> Signed-off-by: Nick Chan <towinchenmi@gmail.com>
>> ---
>>  drivers/tty/serial/samsung_tty.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
>> index c4f2ac9518aa..27b8a50bd3e7 100644
>> --- a/drivers/tty/serial/samsung_tty.c
>> +++ b/drivers/tty/serial/samsung_tty.c
>> @@ -2536,7 +2536,7 @@ static const struct s3c24xx_serial_drv_data s5l_serial_drv_data = {
>>  		.name		= "Apple S5L UART",
>>  		.type		= TYPE_APPLE_S5L,
>>  		.port_type	= PORT_8250,
>> -		.iotype		= UPIO_MEM,
>> +		.iotype		= UPIO_MEM32,
>>  		.fifosize	= 16,
>>  		.rx_fifomask	= S3C2410_UFSTAT_RXMASK,
>>  		.rx_fifoshift	= S3C2410_UFSTAT_RXSHIFT,
>> @@ -2825,8 +2825,10 @@ static int __init apple_s5l_early_console_setup(struct earlycon_device *device,
>>  	/* Close enough to S3C2410 for earlycon... */
>>  	device->port.private_data = &s3c2410_early_console_data;
>>  
>> +	/* ... however, we need to change the port iotype */
>> +	device->port.iotype = UPIO_MEM32;
> 
> If there is going to be resend, then this comment is redundant and can
> be dropped - repeats the code and does not provide any explanation why.
> 
> Which would also make the patch smaller and easier to read. See GS101
> earlycon.
I agree that the comment is quite useless as-is. However, I think it is
worthwhile to mention that A7-A11 expect MMIO32 register accesses here,
as someone looking at this code is likely using one of the newer SoCs,
which does not have this restriction.

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

Nick Chan