Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle configuration

David Lechner
2024-06-06T13:21:04Z

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