On 6/07/19 2:20 PM, Angelo Dureghello wrote:
Hi Adrian,
On Tue, Jul 02, 2019 at 12:10:54PM +0300, Adrian Hunter wrote:
On 20/06/19 1:22 AM, Angelo Dureghello wrote:
Hi Christoph,
On Sun, Jun 16, 2019 at 11:58:07PM -0700, Christoph Hellwig wrote:
On Sun, Jun 16, 2019 at 10:48:21PM +0200, Angelo Dureghello wrote:
This driver has been developed as a separate module starting
from the similar sdhci-esdhc-fls.c.
Separation has been mainly driven from change in endianness.
Can't we have a way to define the endianess at build or even runtime?
We have plenty of that elsewhere in the kernel.
well, the base sdhci layer wants to access byte-size fields of the
esdhc controller registers.
But this same Freescale esdhc controller may be found in 2
flavors, big-endian or little-endian organized.
So in this driver i am actually correcting byte-addresses to
access the wanted byte-field in the big-endian hw controller.
So this is a bit different from a be-le endian swap of a
long or a short that the kernel is organized to do..
Did you consider just using different sdhci_ops so that you could support
different sdhci I/O accessors?
Initially i tried to modify the IMX/Vybrid (arm) driver. But was stopped from
several points, trying to remember now,
- the I/O accessors was a const struct, but this of course is not a big
issue,
- here and there bitfields and positions of the ColdFire controller
registers, compared to the arm versions, are different, so controller hw
is not exactly the same,
- on ColdFire controller and some behaviors and errata are different,
- dma endiannes not hw-configurable,
- ColdFire has max clock limitations, a bit different clock init.
Finally, since there is already a common library (shdci.c) i decided to go
as a separate driver, instead of filling the driver of "if (coldfire)" also
mainly for the following reasons:
1) separated ColdFire driver has a quite small amount of code, simple to
understand.
2) having drivers used by multiple architectures, it add risks, each time
i perform a change, i can test it only on ColdFire, and can break
the driver for the other architectures (i see this not rarely happening for
multiple-arch used drivers).
So let me know if the way chosen can be ok. Otherwise i will roll back
trying to modify the iMX/Vybrid driver, likely adding a lot of "if (coldfire)"
complicating it quite a lot.
"if (coldfire)" is not very nice, and there doesn't seem to be that much
common code, so let's stick with a separate driver, but please change the
commit message in consideration of this discussion.
