Received-SPF: pass (google.com: domain of linux-kernel+bounces-204353-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <f8ce5dc8-ed68-4f04-af3a-187bf0e4a3b3@baylibre.com>
Date: Thu, 6 Jun 2024 08:21:02 -0500
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle
 configuration
To: =?UTF-8?Q?Nuno_S=C3=A1?= <noname.nuno@gmail.com>,
 Marcelo Schmitt <marcelo.schmitt@analog.com>, broonie@kernel.org,
 lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org,
 robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
 nuno.sa@analog.com, marcelo.schmitt1@gmail.com
Cc: linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
 linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1717539384.git.marcelo.schmitt@analog.com>
 <a6b00e84325bbe44919cc49509e837f2555367d0.1717539384.git.marcelo.schmitt@analog.com>
 <ed4fe3de-726b-4eba-a12a-d2f7b1da26d1@baylibre.com>
 <0e18b3aa83a62103b0f06ee516193c03f80abae9.camel@gmail.com>
Content-Language: en-US
From: David Lechner <dlechner@baylibre.com>
In-Reply-To: <0e18b3aa83a62103b0f06ee516193c03f80abae9.camel@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

On 6/6/24 1:51 AM, Nuno Sá wrote:
> On Wed, 2024-06-05 at 12:03 -0500, David Lechner wrote:
>> On 6/4/24 5:43 PM, Marcelo Schmitt wrote:
>>> Implement MOSI idle low and MOSI idle high to better support peripherals
>>> that request specific MOSI behavior.
>>>
>>> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
>>> ---
>>>  drivers/spi/spi-axi-spi-engine.c | 8 +++++++-
>>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-
>>> engine.c
>>> index 0aa31d745734..549f03069d0e 100644
>>> --- a/drivers/spi/spi-axi-spi-engine.c
>>> +++ b/drivers/spi/spi-axi-spi-engine.c
>>> @@ -41,6 +41,7 @@
>>>  #define SPI_ENGINE_CONFIG_CPHA			BIT(0)
>>>  #define SPI_ENGINE_CONFIG_CPOL			BIT(1)
>>>  #define SPI_ENGINE_CONFIG_3WIRE			BIT(2)
>>> +#define SPI_ENGINE_CONFIG_SDO_IDLE		BIT(3)
>>>  
>>>  #define SPI_ENGINE_INST_TRANSFER		0x0
>>>  #define SPI_ENGINE_INST_ASSERT			0x1
>>> @@ -132,6 +133,10 @@ static unsigned int spi_engine_get_config(struct
>>> spi_device *spi)
>>>  		config |= SPI_ENGINE_CONFIG_CPHA;
>>>  	if (spi->mode & SPI_3WIRE)
>>>  		config |= SPI_ENGINE_CONFIG_3WIRE;
>>> +	if (spi->mode & SPI_MOSI_IDLE_HIGH)
>>> +		config |= SPI_ENGINE_CONFIG_SDO_IDLE;
>>> +	if (spi->mode & SPI_MOSI_IDLE_LOW)
>>> +		config &= ~SPI_ENGINE_CONFIG_SDO_IDLE;
>>>  
>>>  	return config;
>>>  }
>>> @@ -645,7 +650,8 @@ static int spi_engine_probe(struct platform_device
>>> *pdev)
>>>  		return ret;
>>>  
>>>  	host->dev.of_node = pdev->dev.of_node;
>>> -	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_3WIRE;
>>> +	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_3WIRE |
>>> SPI_MOSI_IDLE_LOW
>>> +			  | SPI_MOSI_IDLE_HIGH;
>>>  	host->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
>>>  	host->max_speed_hz = clk_get_rate(spi_engine->ref_clk) / 2;
>>>  	host->transfer_one_message = spi_engine_transfer_one_message;
>>
>> I think we need a version check instead of setting the flags unconditionally
>> here since older versions of the AXI SPI Engine won't support this feature.
> 
> Oh, was not aware of that... Then, we definitely need to do that. Marcelo, only
> add my r-b tag with the version change in place.
> 
> - Nuno Sá

Actually, looking at [1], it looks like this could be a compile-time
flag when the HDL is built. If it stays that way, then we would need
a way to read that flag from a register instead of using the version.


[1]: https://github.com/analogdevicesinc/hdl/pull/1320#issuecomment-2145744521