Hello.
Pawel Moll wrote:
VE suffers from serious problem with MMC transfers - low performance, errors when other IO peripherals (especially USB) are used at the same time etc.
It all boils down to the MMC controller short FIFO and - in result - timing constrains. The most problematic case - USB driver hogging CPU and MMC FIFO under/overruns in the result - can be mitigated on SMP system by distributing interrupts handling for these peripherals between cores.
With this, the MMC card clock can be safely (at least it looks like it) increased to 1.5MHz, improving performance.
Signed-off-by: Pawel Moll pawel.moll@arm.com
arch/arm/mach-vexpress/v2m.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/arch/arm/mach-vexpress/v2m.c b/arch/arm/mach-vexpress/v2m.c index 4b5af01..300ac72 100644 --- a/arch/arm/mach-vexpress/v2m.c +++ b/arch/arm/mach-vexpress/v2m.c
[...]
static AMBA_DEVICE(aaci, "mb:aaci", V2M_AACI, NULL); @@ -391,6 +392,19 @@ static void __init v2m_init(void) for (i = 0; i < ARRAY_SIZE(v2m_amba_devs); i++) amba_device_register(v2m_amba_devs[i], &iomem_resource);
- /* WARNING: HACK HACK HACK!
** MMCI cell has very tight timing requirements regarding interrupt* handling (fractions of millisecond), while the USB host controller* interrupt handler can hog the CPU for more then 1 millisecond!** To mitigate the problem on SMP systems, we can set CPU affinities* of these interrupts to different cores... */
The preferred style for the mutli-line comments is this:
/* * bla * bla */
You were close. :-)
- BUG_ON(v2m_usb_resources[1].flags != IORESOURCE_IRQ);
- irq_set_affinity(v2m_usb_resources[1].start, cpumask_of(0));
- irq_set_affinity(mmci_device.irq[0], cpumask_of(1));
- irq_set_affinity(mmci_device.irq[1], cpumask_of(1));
- pm_power_off = v2m_power_off; arm_pm_restart = v2m_restart;
WBR, Sergei