Re: [PATCH 06/32] spi: dw: Add support for the Kendryte K210 SoC

[Sean Anderson <seanga2@xxxxxxxxx>]

On 11/7/20 8:42 AM, Damien Le Moal wrote:
> On 2020/11/07 22:31, Sean Anderson wrote:
>> On 11/7/20 3:13 AM, Damien Le Moal wrote:
>>> The DW SPI master of the Kendryte K210 RISC-V SoC uses the 32-bits
>>> ctrlr0 register format. This SoC is also quite slow and gets significant
>>> SD card performance improvements from using no-delay polled transfers.
>>> Add the dw_spi_k210_init() function tied to the
>>> "canaan,kendryte-k210-spi" compatible string to set the
>>> DW_SPI_CAP_DFS_32 and DW_SPI_CAP_POLL_NODELAY DW SPI capability fields
>>> for this SoC.
>>>
>>> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
>>> ---
>>>  drivers/spi/spi-dw-mmio.c | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
>>>
>>> diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
>>> index 3f1bc384cb45..a00def6c5b39 100644
>>> --- a/drivers/spi/spi-dw-mmio.c
>>> +++ b/drivers/spi/spi-dw-mmio.c
>>> @@ -223,6 +223,14 @@ static int dw_spi_keembay_init(struct platform_device *pdev,
>>>  	return 0;
>>>  }
>>>  
>>> +static int dw_spi_k210_init(struct platform_device *pdev,
>>> +			    struct dw_spi_mmio *dwsmmio)
>>> +{
>>> +	dwsmmio->dws.caps = DW_SPI_CAP_DFS_32 | DW_SPI_CAP_POLL_NODELAY;
>>
>> Can't you do runtime detection of DFS_32 in probe?
> 
> I think it is possible, but it was much easier this way given that it seems that
> only the K210 uses the DFS_32.

I think if it is detectable at runtime it should be, instead of relying
on compatible strings. That way causes less future grief to anyone
porting a device possibly using DFS_32.

 --Sean

>>> +
>>> +	return 0;
>>> +}
>>> +
>>>  static int dw_spi_mmio_probe(struct platform_device *pdev)
>>>  {
>>>  	int (*init_func)(struct platform_device *pdev,
>>> @@ -340,6 +348,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
>>>  	{ .compatible = "snps,dwc-ssi-1.01a", .data = dw_spi_dwc_ssi_init},
>>>  	{ .compatible = "intel,keembay-ssi", .data = dw_spi_keembay_init},
>>>  	{ .compatible = "microchip,sparx5-spi", dw_spi_mscc_sparx5_init},
>>> +	{ .compatible = "canaan,kendryte-k210-spi", .data = dw_spi_k210_init},
>>>  	{ /* end of table */}
>>>  };
>>>  MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
>>>
>>
>>
> 
>