On Tue, 2007-10-30 at 13:05 -0700, David Brownell wrote:
> On Tuesday 30 October 2007, Bryan Wu wrote:
> > Current SPI driver enables SPI controller and set the SPI baud register
> > for each SPI transfer. But, they should never be changed within a SPI
> > message session, in which seveal SPI transfers are pumped.
>
> That's actually not true. If a driver sets spi_transfer.max_speed_hz
> to a nonzero value that's different from the previous bit rate (which
> may be spi_device.max_speed_hz), it should be updated before that
> transfer segment. Example, sometimes data can't be clocked out at
> the same rate commands can be clocked in.
>
> Similarly with spi_transfer.bits_per_word ... again, it's very possible
> that commands and data have different sizes.
>
I agree with you here.
Maybe there are some confusion of mixing up the spi_trasnfer.speed_hz
with the spi_device.max_speed_hz.
spi_device.max_speed_hz comes from spi_board_info.max_speed_hz, it is
for the default max speed value.
spi_transfer.speed_hz comes from upper applications for each spi
transfer setting.
Am I right?
I will fix this later.
> Of course, if those values don't change, there'd be no point in
> reconfiguring any aspect of those communications parameters...
>
>
> I'll be forwarding this patch, since this looks like another case
> where the main effect of the patch doesn't match its description
> and since this patch series has taken too long already. (Does this
> patch even really relate primarily to working with an ST M25P16
> flash part??) Though it'd be reasonable to be more hard-nosed
> about this and insist on another go-around for thesse patches.
> (Making this the fifth one??)
>
> But I *STRONGLY* suggest someone revisit the issue of whether those
> two per-transfer options are now being handled correctly. As well
> as update procedures so that the patch comments start to have a
> direct correspondence to what the patches have changed...
>
OK, we will test this on our hardware.
Thanks, Dave
-Bryan Wu
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
