Re: [PATCH] spi: dw: Set default value if reg-io-width isn't specified

From: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: Mark Brown <broonie@kernel.org>,
	linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] spi: dw: Set default value if reg-io-width isn't specified
Date: Tue, 8 Aug 2023 09:00:18 +0900	[thread overview]
Message-ID: <213763b3-5a8b-3a88-54f1-024325f7fe80@socionext.com> (raw)
In-Reply-To: <az7wvv5f42mnuuwkqzpfmwg4ngvl4jvpcfmns7d6lhzogc4qdi@ox64l6i7b44r>

Hi Serge,

On 2023/08/08 7:57, Serge Semin wrote:
> On Mon, Aug 07, 2023 at 09:16:21AM +0900, Kunihiko Hayashi wrote:
>> According to the dt-bindings, the default value of reg-io-width is 4.
>> However, the value becomes zero when reg-io-width isn't specified.
> 
> This semantic is implied by the dw_read_io_reg() and dw_write_io_reg()
> methods. It doesn't seem like that much necessary duplicating it in the
> property parse procedure, if not to say - redundant.

I see. Currently since the variable reg_io_width has no other references
other than dw_{read, write}_io_reg(), it means the default value is taken
if this is zero.

So, I think we should be careful when actually using the value of
this variable.

Thank you,

> 
> -Serge(y)
> 
>>
>> Should set the actual value to dws->reg_io_width, considering it
>> referenced.
>>
>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
>> ---
>>   drivers/spi/spi-dw-mmio.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
>> index a963bc96c223..7eafc07ef7aa 100644
>> --- a/drivers/spi/spi-dw-mmio.c
>> +++ b/drivers/spi/spi-dw-mmio.c
>> @@ -369,7 +369,9 @@ static int dw_spi_mmio_probe(struct platform_device
> *pdev)
>>   
>>   	dws->max_freq = clk_get_rate(dwsmmio->clk);
>>   
>> -	device_property_read_u32(&pdev->dev, "reg-io-width",
> &dws->reg_io_width);
>> +	if (device_property_read_u32(&pdev->dev, "reg-io-width",
>> +				     &dws->reg_io_width))
>> +		dws->reg_io_width = 4;
>>   
>>   	num_cs = 4;
>>   
>> -- 
>> 2.25.1
>>

---
Best Regards
Kunihiko Hayashi