Hi Paul, On 10/30/2012 05:05 AM, Paul Walmsley wrote: > omap_hwmod: mcpdm: cannot be enabled for reset (3) > > The McPDM on OMAP4 can only receive its functional clock from an > off-chip source. This source is not guaranteed to be present on the > board, and when present, it is controlled by I2C. This would > introduce a board dependency to the early hwmod code which it was not > designed to handle. Also, neither the driver for this off-chip clock > provider nor the I2C code is available early in boot when the hwmod > code is attempting to enable and reset IP blocks. This effectively > makes it impossible to enable and reset this device during hwmod init. > > At its core, this patch is a workaround for an OMAP hardware problem. > It should be possible to configure the OMAP to provide any IP block's > functional clock from an on-chip source. (This is true for almost > every IP block on the chip. As far as I know, McPDM is the only > exception.) If the kernel cannot reset and configure IP blocks, it > cannot guarantee a sane SoC state. Relying on an optional off-chip > clock also creates a board dependency which is beyond the scope of the > early hwmod code. > > This patch works around the issue by marking the McPDM hwmod record > with the HWMOD_EXT_OPT_MAIN_CLK flag. This prevents the hwmod > code from touching the device early during boot. > > Signed-off-by: Paul Walmsley <[email protected]> > Cc: Péter Ujfalusi <[email protected]> > Cc: Benoît Cousson <[email protected]>
Acked-by: Peter Ujfalusi <[email protected]> > --- > arch/arm/mach-omap2/omap_hwmod_44xx_data.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm/mach-omap2/omap_hwmod_44xx_data.c > b/arch/arm/mach-omap2/omap_hwmod_44xx_data.c > index 652d028..7bddfa5 100644 > --- a/arch/arm/mach-omap2/omap_hwmod_44xx_data.c > +++ b/arch/arm/mach-omap2/omap_hwmod_44xx_data.c > @@ -2125,6 +2125,14 @@ static struct omap_hwmod omap44xx_mcpdm_hwmod = { > .name = "mcpdm", > .class = &omap44xx_mcpdm_hwmod_class, > .clkdm_name = "abe_clkdm", > + /* > + * It's suspected that the McPDM requires an off-chip main > + * functional clock, controlled via I2C. This IP block is > + * currently reset very early during boot, before I2C is > + * available, so it doesn't seem that we have any choice in > + * the kernel other than to avoid resetting it. > + */ > + .flags = HWMOD_EXT_OPT_MAIN_CLK, > .mpu_irqs = omap44xx_mcpdm_irqs, > .sdma_reqs = omap44xx_mcpdm_sdma_reqs, > .main_clk = "mcpdm_fck", > -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
