On Thu, Sep 12, 2013 at 04:22:02PM +0100, David Woodhouse wrote:
> On Thu, 2013-09-12 at 22:58 -0400, Huang Shijie wrote:
> >
> > But for the quadspi driver, it does not need this information.
> >
> > When the drivers knows that it is a Quad-read transaction, it will uses
> > the relative LUT sequence which uses the 4 lines.
>
> But the controller driver shouldn't *have* that incestuous knowledge of
> the command set of the chip that happens to be connected to it.
I think the controller is designed for the NOR flash, yes, a little
strange.
>
> That's what we're *complaining* about.
>
> It *should* "need this information", and should just do what it's *told*
> to do by the slave device driver.
I can add the lines info in the m25p80_read() for the quad-read, but the lines
information is redundant to this Quadspi driver.
I will send you the datasheet tomorrow.
Mark and you want to create the LUT instruction sequence at the runtime,
But there is some disadvantage if we do so:
[1] low efficiency:
If you want to change the LUT regitster, you should unlock the LUT
register, and change the LUT regitsters, and lock the LUT
regitsters again.
[2] we may can not create all the LUT instruction sequence at the
runtime. For example, the buffer program(OPCODE_PP):
the m25p80_write() may write 256bytes at a time, but the Quadspi
controller only has a 64-byte TX-FIFO, so the controller should
write a 64bytes firstly, then sends to the NOR with a read-status
command. Do you want to create a read-status LUT instruction
sequence at run time? This is not good solution, we should
pre-populate the read-status LUT information.
[3] We may can not create the LUT instruction sequence at the runtime,
since we can not get enough information from the spi_transfer{}.
A whole LUT instruction sequence may needs the following info:
1.) spi command.
2.) lines info: single line, dual lines, quad lines.
3.) Address width: 3 bytes address or 4 bytes address.
4.) instruction type: Read or write or other.
5.) length info: how many bytes for this transaction .
6.) dummy info: how many dummy is needed for this transaction.
We can not get the dummy info from the spi_transfer{}
I may still miss something. But If we want to create a LUT
instruction sequence at the runtime, we should _PARSE_ out the SPI
NOR command firstly. If we parse out the SPI nor commands, there
is no difference between the pre-populete-LUT and
create-LUT-at-runtime.
thanks
Huang Shijie
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
