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charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Last-TLS-Session-Version: TLSv1.3 Hi Santhosh, >> This information is currently lacking indeed, mostly because nobody >> ever >> cared about it. The DT property is IMO not the correct way to give this >> information for two reasons: >> - this is a capability of the chip, we discover the chip dynamically in >> both cases (NAND and NOR) and attach many capabilities to the chips >> already, so I believe this information should be provided through a >> flag. >> - the fact that the DQS signal might be supported does not indicate it >> is actually driven. Winbond chips, for instance, can either enable it >> or not depending on their configuration (probably through their VCR >> register, I need to check again). > > I agree. The flash device's capability to provide DQS - whether in SDR, > DDR or both modes - can be represented as a flag in the flash > description. We can list out the possible combinations and use them to > clearly describe the flash's supported capabilities. > > However, whether the DQS signal is actually connected to the controller > is a non-discoverable hardware detail and should be described only via > Device Tree. The DT property is not meant to describe the flash's > capabilities, but to indicate whether DQS is physically connected to the > controller. > >> The question I have is: shall we enable the DQS pin automatically if >> it >> is available? Not all controllers support it I suppose, and wiring the >> line might as well not be done (or incorrectly). For these cases we may >> need DT properties in the future. But for the DQS presence indication, I >> bet it is not useful, and should be handled at the core level (not >> parsed by the driver like you do) because it may have an impact on the >> chip internal configuration. > > We can handle this in either way: keep DQS disabled by default and > enable it using a "has-dqs" property, or enable it by default and > disable it explicitly using a "no-dqs" property. I know we can be surprised by our hardware colleagues :-), but I would consider "not wiring the DQS signal of a (DQS capable) octal DTR SPI memory" a bug? Hence I would opt for handling the broken case, when/if that need arises. Thanks, Miqu=C3=A8l