Re: [PATCH v2 21/28] spi: s3c64xx: infer fifosize from the compatible

[Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>]

On 1/25/24 22:28, Sam Protsenko wrote:
> On Thu, Jan 25, 2024 at 8:50 AM Tudor Ambarus <tudor.ambarus@xxxxxxxxxx> wrote:
>> Infer the FIFO size from the compatible, where all the instances of the
>> SPI IP have the same FIFO size. This way we no longer depend on the SPI
>> alias from the device tree to select the FIFO size, thus we remove the
>> dependency of the driver on the SPI alias.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
>> ---
>>  drivers/spi/spi-s3c64xx.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index 5a93ed4125b0..b86eb0a77b60 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -1381,7 +1381,7 @@ static const struct dev_pm_ops s3c64xx_spi_pm = {
>>  };
>>
>>  static const struct s3c64xx_spi_port_config s3c2443_spi_port_config = {
>> -       .fifo_lvl_mask  = { 0x7f },
> How will it work with already existing out-of-tree dts's, if only
> kernel image gets updated? I wonder if it's considered ok to break
> that compatibility like this.
> 

ah, good catch, Sam! I prepared everything to not break older device
trees and then I removed this :).

>> +       .fifosize       = 64,

Adding .fifosize and keeping fifo_lvl_mask will not break backward
compatibility. In s3c64xx_spi_get_fifosize() I first check if .fifosize
is set and use that, and if not set, use the .fifo_lvl_mask.