linux-kernel - Re: [PATCH 4/6] tty: serial: lpuart: add imx7ulp support

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Message-ID: <CAA+hA=RDjRwwT-O5Y3z-AAQxtPDU7agZdGe6KeFTT=QoW3ufFw@mail.gmail.com>
Date:   Wed, 10 May 2017 14:14:25 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Dong Aisheng <aisheng.dong@....com>, linux-serial@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        gregkh <gregkh@...uxfoundation.org>, jslaby@...e.com,
        Fugang Duan <fugang.duan@....com>, Mingkai.Hu@....com,
        yangbo.lu@....com
Subject: Re: [PATCH 4/6] tty: serial: lpuart: add imx7ulp support

Hi Stefan,

On Wed, May 10, 2017 at 12:10 PM, Stefan Agner <stefan@...er.ch> wrote:
> On 2017-05-09 00:50, Dong Aisheng wrote:
>> The lpuart of imx7ulp is basically the same as ls1021a. It's also
>> 32 bit width register, but unlike ls1021a, it's little endian.
>> Besides that, imx7ulp lpuart has a minor different register layout
>> from ls1021a that it has four extra registers (verid, param, global,
>> pincfg) located at the beginning of register map, which are currently
>> not used by the driver and less to be used later.
>>
>> To ease the register difference handling, we add a reg_off member
>> in lpuart_soc_data structure to represent if the normal
>> lpuart32_{read|write} requires plus a offset to hide the issue.
>>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Jiri Slaby <jslaby@...e.com>
>> Cc: Fugang Duan <fugang.duan@....com>
>> Cc: Stefan Agner <stefan@...er.ch>
>> Cc: Mingkai Hu <Mingkai.Hu@....com>
>> Cc: Yangbo Lu <yangbo.lu@....com>
>> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
>> ---
>>  drivers/tty/serial/fsl_lpuart.c | 21 ++++++++++++++++++---
>>  1 file changed, 18 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
>> index bddd041..1cdb3f9 100644
>> --- a/drivers/tty/serial/fsl_lpuart.c
>> +++ b/drivers/tty/serial/fsl_lpuart.c
>> @@ -231,7 +231,11 @@
>>  #define DEV_NAME     "ttyLP"
>>  #define UART_NR              6
>>
>> +/* IMX lpuart has four extra unused regs located at the beginning */
>> +#define IMX_REG_OFF  0x10
>> +
>>  static bool lpuart_is_be;
>> +static u8 lpuart_reg_off;
>
> Global variables? That hardly works once you have two UARTs...
>

lpuart_reg_off is SoC specific and there's no two UART
with two different reg offset.

> Instead of adding a fixed offset to any write you could just add the
> offset to sport->port.membase...
>

That's intended as i don't want the changes to be too intrusive.
If adding offset in sport->port.xxx, then we have to change the basic
lpuart32_read/write API which is called through the whole driver.

Regards
Dong Aisheng

> --
> Stefan
>
>>
>>  struct lpuart_port {
>>       struct uart_port        port;
>> @@ -263,6 +267,7 @@ struct lpuart_port {
>>  struct lpuart_soc_data {
>>       bool    is_32;
>>       bool    is_be;
>> +     u8      reg_off;
>>  };
>>
>>  static struct lpuart_soc_data vf_data = {
>> @@ -272,11 +277,19 @@ static struct lpuart_soc_data vf_data = {
>>  static struct lpuart_soc_data ls_data = {
>>       .is_32 = true,
>>       .is_be = true,
>> +     .reg_off = 0x0,
>> +};
>> +
>> +static struct lpuart_soc_data imx_data = {
>> +     .is_32 = true,
>> +     .is_be = false,
>> +     .reg_off = IMX_REG_OFF,
>>  };
>>
>>  static const struct of_device_id lpuart_dt_ids[] = {
>>       { .compatible = "fsl,vf610-lpuart", .data = &vf_data, },
>>       { .compatible = "fsl,ls1021a-lpuart", .data = &ls_data, },
>> +     { .compatible = "fsl,imx7ulp-lpuart", .data = &imx_data, },
>>       { /* sentinel */ }
>>  };
>>  MODULE_DEVICE_TABLE(of, lpuart_dt_ids);
>> @@ -286,15 +299,16 @@ static void lpuart_dma_tx_complete(void *arg);
>>
>>  static u32 lpuart32_read(void __iomem *addr)
>>  {
>> -     return lpuart_is_be ? ioread32be(addr) : readl(addr);
>> +     return lpuart_is_be ? ioread32be(addr + lpuart_reg_off) :
>> +                           readl(addr + lpuart_reg_off);
>>  }
>>
>>  static void lpuart32_write(u32 val, void __iomem *addr)
>>  {
>>       if (lpuart_is_be)
>> -             iowrite32be(val, addr);
>> +             iowrite32be(val, addr + lpuart_reg_off);
>>       else
>> -             writel(val, addr);
>> +             writel(val, addr + lpuart_reg_off);
>>  }
>>
>>  static void lpuart_stop_tx(struct uart_port *port)
>> @@ -2008,6 +2022,7 @@ static int lpuart_probe(struct platform_device *pdev)
>>       sport->port.line = ret;
>>       sport->lpuart32 = sdata->is_32;
>>       lpuart_is_be = sdata->is_be;
>> +     lpuart_reg_off = sdata->reg_off;
>>
>>       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>       sport->port.membase = devm_ioremap_resource(&pdev->dev, res);