[U-Boot] [PATCH] DW SPI: Allow to overload the management of the external CS

[Gregory CLEMENT <gregory.clement@bootlin.com>]

Hi Daniel,
 
 On mer., sept. 26 2018, Daniel Schwierzeck <daniel.schwierzeck@gmail.com> wrote:

> On 25.09.2018 15:17, Gregory CLEMENT wrote:
>> On some platforms, as the Ocelot ones, when wanting to control the CS
>> through software, it is not possible to do it through the GPIO
>> controller. Indeed, this signal is managed through a dedicated range of
>> registers inside the SoC..
>
> and why did you add a spi-bitbang-gpio driver?

Because the DW SPI is not available on Luton, so for Luton we can only
use a spi-bitbang-gpio driver which is very slow.

Gregory

>
>> 
>> By declaring the external_cs_manage function as weak, it is possible to
>> manage the CS at platform level and then using the appropriate registers.
>> 
>> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
>> ---
>>  drivers/spi/designware_spi.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/spi/designware_spi.c b/drivers/spi/designware_spi.c
>> index d8b73ea326..fe6e753bff 100644
>> --- a/drivers/spi/designware_spi.c
>> +++ b/drivers/spi/designware_spi.c
>> @@ -334,7 +334,13 @@ static int poll_transfer(struct dw_spi_priv *priv)
>>  	return 0;
>>  }
>>  
>> -static void external_cs_manage(struct udevice *dev, bool on)
>> +/*
>> + * We define external_cs_manage function as 'weak' as some targets
>> + * (like OCELOT) don't control the external CS pin using a GPIO
>> + * controller. These SoCs use specific registers to controll by
>> + * software the SPI pins (and especially the CS).
>> + */
>> +__weak void external_cs_manage(struct udevice *dev, bool on)
>>  {
>>  #if defined(CONFIG_DM_GPIO) && !defined(CONFIG_SPL_BUILD)
>>  	struct dw_spi_priv *priv = dev_get_priv(dev->parent);
>> 
>
> -- 
> - Daniel
>

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com