On Thursday 25 September 2014 19:39:34 Felipe Balbi wrote:

quoted

why would a glue layer need to access registers from the core ? That
sounds very odd. I haven't seen that and will, definitely, NACK such a
patch 

can you further describe why you think a glue layer might need to access
core IP's registers ?

I just realised we're talking about chipidea here... in any case, it's
still valid to ask why would glue need to fiddle with core IP's
registers.

Generally, the glue driver wouldn't access the registers, but I don't
think it's important to prevent it from doing that. In some cases, 
a glue driver needs to override a function of the core driver, e.g.
to work around an errata. We have a lot of those quirks in ATA drivers,
one example from ahci_mvebu.c is

static void ahci_mvebu_regret_option(struct ahci_host_priv *hpriv)
{
        /*
         * Enable the regret bit to allow the SATA unit to regret a
         * request that didn't receive an acknowlegde and avoid a
         * deadlock
         */
        writel(0x4, hpriv->mmio + AHCI_VENDOR_SPECIFIC_0_ADDR);
        writel(0x80, hpriv->mmio + AHCI_VENDOR_SPECIFIC_0_DATA);
}

	Arnd