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.
