[PATCH 2/2] spi: dual and quad support(device tree)

[yuhang wang]

Hi, Pekon

2013/8/26 Gupta, Pekon <pekon at ti.com>:
>>
>> fix one thing in patch:
>> commit id:f477b7fb13df2b843997559ff34e87d054ba6538
>>
>> change property spi-tx-nbits and spi-rx-nbits to optional.
>> If User don't set spi-tx-nbits or spi-rx-nbits, spi device mode
>> should be regarded as SINGLE, not return an error.
>>
>> Signed-off-by: wangyuhang <wangyuhang2014 at gmail.com>
>> ---
>>  drivers/spi/spi.c |   68 +++++++++++++++++++++++++--------------------------
>> --
>>  1 file changed, 32 insertions(+), 36 deletions(-)
>>
>> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
>> index 50f7fc3..46a55f0 100644
>> --- a/drivers/spi/spi.c
>> +++ b/drivers/spi/spi.c
>> @@ -872,46 +872,42 @@ static void of_register_spi_devices(struct
>> spi_master *master)
>>               /* Device DUAL/QUAD mode */
>>               prop = of_get_property(nc, "spi-tx-nbits", &len);
>>               if (!prop || len < sizeof(*prop)) {
>> -                     dev_err(&master->dev, "%s has no 'spi-tx-nbits'
>> property\n",
>> -                             nc->full_name);
>> -                     spi_dev_put(spi);
>> -                     continue;
>> -             }
>> -             switch (be32_to_cpup(prop)) {
>> -             case SPI_NBITS_SINGLE:
>> -                     break;
>> -             case SPI_NBITS_DUAL:
>> -                     spi->mode |= SPI_TX_DUAL;
>> -                     break;
>> -             case SPI_NBITS_QUAD:
>> -                     spi->mode |= SPI_TX_QUAD;
>> -                     break;
>> -             default:
>> -                     dev_err(&master->dev, "spi-tx-nbits value is not
>> supported\n");
>> -                     spi_dev_put(spi);
>> -                     continue;
>> +                     /* set tx mode in SINGLE as default */
> [Pekon]: I think you should explicitly set, and not trust spi->mode defaults.
>         spi->mode |= SPI_TX_SINGLE;
>
Now @spi_device->mode [bit8: SPI_TX_DUAL] [bit9: SPI_TX_QUAD] [bit10:
SPI_RX_DUAL] [bit11: SPI_RX_QUAD]. Because to every spi controller,
SPI SINGLE must be supported, so I did not add that as a mode. My
initial thought is if user don't select SPI_TX_DUAL and SPI_TX_QUAD,
then it is TX_SINGLE mode[bit8: 0 bit9: 0].
Now 2 approaches as follows:
1) #define SPI_TX_SINGLE ~(SPI_TX_DUAL | SPI_TX_QUAD)
    case SPI_NBITS_SINGLE:
            spi->mode & SPI_TX_SINGLE;
            break;
2)Adding a new bit in mode to specify SPI_SINGLE. But this bit also
should be reflected to @master->mode_bits. To the probe of each spi
controller driver, it is necessary to do "master->mode_bits |=
SPI_TX_SINGLE | SPI_RX_SINGLE;", in such case, it's not like a
selected mode, it's like a compulsary condition. Since all controller
do support, there's no need to make it a mode.

So I prefer the previous correction, what's your idea.

Best regards