Re: [PATCH v2 23/28] spi: s3c64xx: retrieve the FIFO size from the device tree

["Arnd Bergmann" <arnd@xxxxxxxx>]

On Fri, Jan 26, 2024, at 20:23, Sam Protsenko wrote:
> On Thu, Jan 25, 2024 at 11:33 AM Mark Brown <broonie@xxxxxxxxxx> wrote:
>>
>> On Thu, Jan 25, 2024 at 02:50:01PM +0000, Tudor Ambarus wrote:
>>
>> > Allow SoCs that have multiple instances of the SPI IP with different
>> > FIFO sizes to specify their FIFO size via the "samsung,spi-fifosize"
>> > device tree property. With this we can break the dependency between the
>> > SPI alias, the fifo_lvl_mask and the FIFO size.
>>
>> OK, so we do actually have SoCs with multiple instances of the IP with
>> different FIFO depths (and who knows what else other differences)?
>
> I think that's why we can see .fifo_lvl_mask[] with different values
> for different IP instances. For example, ExynosAutoV9 has this (in
> upstream driver, yes):
>
>     .fifo_lvl_mask = { 0x1ff, 0x1ff, 0x7f, 0x7f, 0x7f, 0x7f, 0x1ff,
> 0x7f, 0x7f, 0x7f, 0x7f, 0x7f},
>

That sounds like the same bug as in the serial port driver,
by assuming that the alias values in the devicetree have
a particular meaning in identifying instances. This immediately
breaks when there is a dtb file that does not use the same
alias values, e.g. because it only needs some of the SPI
ports.

      Arnd