Dear Kevin Cernekee, > On Sat, Aug 25, 2012 at 12:36 PM, Marek Vasut <[email protected]> wrote: > > Add DT property "m25p,fast-read" that signalises the particular > > chip supports "fast read" opcode. > > This might be slightly clearer if it is rephrased as: > > Add DT property "m25p,fast-read" that signifies whether the "fast > read" opcode is supported.
What's the difference? > > +Optional properties: > > +- m25p,fast-read : Use the "fast read" opcode to read data from the chip > > instead + of the usual "read" opcode. This opcode isn > > not supported by + all chips and support for it can > > not be detected at runtime. > > "is not supported" Thanks > Are there any modern SPI flash parts that can't handle FAST_READ, or > is this mostly for compatibility with legacy systems? We have to support all possibilities, not only "modern systems" . > > + bool fast_read; > > > > - t[0].len = m25p_cmdsz(flash) + FAST_READ_DUMMY_BYTE; > > + t[0].len = m25p_cmdsz(flash) + (flash->fast_read ? 1 : 0); > > Newer devices support a variable number of dummy cycles; increasing > the number of dummy cycles can allow for higher interface speeds. One > example is the Macronix MX25L25635F: > > http://bit.ly/P9s7UM Good, but I don't see it supported in the driver, how is this different from MX25L256E? Besides, I noticed the fast-read isn't even properly excersized, as it always reads blocks of 512 bytes, even if it can read any basically length. Why is that, MTD layer stuff or something? > It might be worth thinking about how to capture this sort of > information in the DT properties, even if current versions of m25p80 > only use a small subset of the device capabilities. They can be added as additional DT props, that should be easy. Best regards, Marek Vasut _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
