linux-kernel - Re: [PATCH 2/6] tty: serial: lpuart: add little endian 32 bit register support

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Date:   Wed, 10 May 2017 14:19:55 +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 2/6] tty: serial: lpuart: add little endian 32 bit
 register support

On Wed, May 10, 2017 at 11:58 AM, Stefan Agner <stefan@...er.ch> wrote:
> On 2017-05-09 00:50, Dong Aisheng wrote:
>> It's based on the exist lpuart32 read/write implementation.
>>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Jiri Slaby <jslaby@...e.com> (supporter:TTY LAYER)
>> 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 | 12 ++++++++++--
>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
>> index cd4e905..bddd041 100644
>> --- a/drivers/tty/serial/fsl_lpuart.c
>> +++ b/drivers/tty/serial/fsl_lpuart.c
>> @@ -231,6 +231,8 @@
>>  #define DEV_NAME     "ttyLP"
>>  #define UART_NR              6
>>
>> +static bool lpuart_is_be;
>> +
>
> Other LS1021a IP's such as SPI use the big-endian device tree property
> along with regmap.
>
> See e.g.
> drivers/spi/spi-fsl-dspi.c
>
> (Used in vf610 in little endian mode and ls1021a in big endian)
>
> Not sure if we want to switch to regmap, but you can also get the
> property using of_get_property.
>
> The ls1021a lpuart node do not specify big-endian at the moment (would
> probably good to add it),

That's why i did not check for little-endian initially.

> so I would leave big-endian the driver default
> and check for little-endian for the new device and check whether that is
> specified:
> of_get_property(dn, "little-endian", NULL)

As we already have the platform data, it's not too necessary to get the endian
from device tree.

Regards
Dong Aisheng

>
> --
> Stefan
>
>>  struct lpuart_port {
>>       struct uart_port        port;
>>       struct clk              *clk;
>> @@ -260,6 +262,7 @@ struct lpuart_port {
>>
>>  struct lpuart_soc_data {
>>       bool    is_32;
>> +     bool    is_be;
>>  };
>>
>>  static struct lpuart_soc_data vf_data = {
>> @@ -268,6 +271,7 @@ static struct lpuart_soc_data vf_data = {
>>
>>  static struct lpuart_soc_data ls_data = {
>>       .is_32 = true,
>> +     .is_be = true,
>>  };
>>
>>  static const struct of_device_id lpuart_dt_ids[] = {
>> @@ -282,12 +286,15 @@ static void lpuart_dma_tx_complete(void *arg);
>>
>>  static u32 lpuart32_read(void __iomem *addr)
>>  {
>> -     return ioread32be(addr);
>> +     return lpuart_is_be ? ioread32be(addr) : readl(addr);
>>  }
>>
>>  static void lpuart32_write(u32 val, void __iomem *addr)
>>  {
>> -     iowrite32be(val, addr);
>> +     if (lpuart_is_be)
>> +             iowrite32be(val, addr);
>> +     else
>> +             writel(val, addr);
>>  }
>>
>>  static void lpuart_stop_tx(struct uart_port *port)
>> @@ -2000,6 +2007,7 @@ static int lpuart_probe(struct platform_device *pdev)
>>       }
>>       sport->port.line = ret;
>>       sport->lpuart32 = sdata->is_32;
>> +     lpuart_is_be = sdata->is_be;
>>
>>       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>       sport->port.membase = devm_ioremap_resource(&pdev->dev, res);