[PATCH] usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP
From: nico@fluxnic.net (Nicolas Pitre)
Date: 2011-08-31 17:46:50
Also in:
linux-omap
On Wed, 31 Aug 2011, Will Deacon wrote:
On Wed, Aug 31, 2011 at 02:43:33PM +0100, Mark Salter wrote:quoted
On Wed, 2011-08-31 at 09:49 +0100, Will Deacon wrote:quoted
On Wed, Aug 31, 2011 at 01:23:47AM +0100, Chen Peter-B29397 wrote:quoted
One question: why this write buffer issue did not happen at UP ARM V7 platform, whose dma buffer also uncache, but bufferable?Which CPU was on this platform?Using a 3.1.0-rc4+ kernel on a Pandaboard, and running 'hdparm -t' on a usb disk drive, I see ~5.8MB/s read speed. Same kernel, but passing nosmp on the commandline, I see 20.3MB/s. Can someone explain why nosmp would make such a difference?Oh gawd, that's horrible. I have a feeling it's probably a separate issue though, caused by: omap_modify_auxcoreboot0(0x200, 0xfffffdff); in boot_secondary for OMAP. Unfortunately I have no idea what that line is doing because it ends up talking to the secure monitor.
Well, this issue is apparently affecting other ARMv9 implementations
too. In which case this code in arch/arm/mm/mmu.c could be responsible:
if (is_smp()) {
/*
* Mark memory with the "shared" attribute
* for SMP systems
*/
user_pgprot |= L_PTE_SHARED;
kern_pgprot |= L_PTE_SHARED;
vecs_pgprot |= L_PTE_SHARED;
mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_S;
mem_types[MT_DEVICE_WC].prot_pte |= L_PTE_SHARED;
mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_S;
mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED;
mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S;
mem_types[MT_MEMORY].prot_pte |= L_PTE_SHARED;
mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_S;
mem_types[MT_MEMORY_NONCACHED].prot_pte |= L_PTE_SHARED;
}
However I don't see the nosmp kernel argument having any effect on the
result from is_smp().
Nicolas