[PATCH 10/16] serial: sh: Add RZ/G2L SCIF support

[Paul Barker]

On 03/10/2023 14:23, Marek Vasut wrote:
> On 9/20/23 14:42, Paul Barker wrote:
>> Extend the existing driver to support the SCIF serial ports on the
>> Renesas RZ/G2L (R9A07G044) SoC. This also requires us to ensure that the
>> relevant reset signal is de-asserted before we try to talk to the SCIF
>> module.
>>
>> Signed-off-by: Paul Barker <paul.barker.ct at bp.renesas.com>
>> Reviewed-by: Biju Das <biju.das.jz at bp.renesas.com>
>> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>
>> ---
>>   arch/arm/mach-rmobile/Kconfig |  1 +
>>   drivers/serial/serial_sh.c    | 32 ++++++++++++++++++++++++++++++--
>>   drivers/serial/serial_sh.h    | 19 ++++++++++++++++++-
>>   3 files changed, 49 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm/mach-rmobile/Kconfig b/arch/arm/mach-rmobile/Kconfig
>> index 973e84fcf7ba..0ab22356aee5 100644
>> --- a/arch/arm/mach-rmobile/Kconfig
>> +++ b/arch/arm/mach-rmobile/Kconfig
>> @@ -77,6 +77,7 @@ config RZG2L
>>   	imply RENESAS_SDHI
>>   	imply CLK_RZG2L
>>   	imply PINCTRL_RZG2L
>> +	imply SCIF_CONSOLE
>>   	help
>>   	  Enable support for the Renesas RZ/G2L family of SoCs, including the
>>   	  the RZ/G2L itself (based on the R9A07G044 SoC).
>> diff --git a/drivers/serial/serial_sh.c b/drivers/serial/serial_sh.c
>> index 5e543dbf3d58..a2e9a57137a6 100644
>> --- a/drivers/serial/serial_sh.c
>> +++ b/drivers/serial/serial_sh.c
>> @@ -17,6 +17,8 @@
>>   #include <linux/compiler.h>
>>   #include <dm/platform_data/serial_sh.h>
>>   #include <linux/delay.h>
>> +#include <dm/device_compat.h>
>> +#include <reset.h>
>>   #include "serial_sh.h"
>>   
>>   DECLARE_GLOBAL_DATA_PTR;
>> @@ -79,8 +81,16 @@ sh_serial_setbrg_generic(struct uart_port *port, int clk, int baudrate)
>>   
>>   static void handle_error(struct uart_port *port)
>>   {
>> -	sci_in(port, SCxSR);
>> -	sci_out(port, SCxSR, SCxSR_ERROR_CLEAR(port));
>> +	/* The RZ/G2L datasheet says that error conditions are cleared by
>> +	 * resetting the error bits in the FSR register to zero.
> 
> Can you be more specific here ?
> 
> It doesn't seem Linux sh-sci.c driver does anything special for G2L, so 
> is this special case really needed ?

On page 1268 of the datasheet (R01UH0914EJ0130 Rev.1.30):

"DR is cleared to 0 when DR = 1 is read and then 0 is written to the DR
flag."

On page 1270:

"[Clearing condition]
● When 0 is written to ER after it has been read as 1"

So zeros must be written to clear these errors, not ones.

We have an open task to investigate the issue in the Linux driver and
fix it.

> 
>> +	 */
>> +	if (IS_ENABLED(CONFIG_RZG2L)) {
>> +		unsigned short status = sci_in(port, SCxSR);
>> +		sci_out(port, SCxSR, status & ~SCIF_ERRORS);
>> +	} else {
>> +		sci_in(port, SCxSR);
>> +		sci_out(port, SCxSR, SCxSR_ERROR_CLEAR(port));
>> +	}
>>   	sci_in(port, SCLSR);
>>   	sci_out(port, SCLSR, 0x00);
>>   }
>> @@ -193,6 +203,23 @@ static int sh_serial_probe(struct udevice *dev)
>>   	priv->type	= plat->type;
>>   	priv->clk_mode	= plat->clk_mode;
>>   
>> +	if (IS_ENABLED(CONFIG_RZG2L)) {
>> +		struct reset_ctl rst;
>> +		int ret;
>> +
>> +		ret = reset_get_by_index(dev, 0, &rst);
>> +		if (ret < 0) {
>> +			dev_err(dev, "failed to get reset line\n");
>> +			return ret;
>> +		}
>> +
>> +		ret = reset_deassert(&rst);
>> +		if (ret < 0) {
>> +			dev_err(dev, "failed to de-assert reset line\n");
>> +			return ret;
>> +		}
>> +	}
> 
> devm_reset_control_get_optional() or something should do here too , right ?
> 
> Note that R-Car does have SCIF reset too, so this can be generic code.

For R-Car systems the current behaviour is working and well tested, we
concluded that we shouldn't change it so this reset de-assert was made
RZ/G2L specific.

For RZ/G2L, de-asserting the reset is not optional.

Thanks,
Paul
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