On Thu, May 14, 2015 at 04:26:45PM +0200, Luis R. Rodriguez wrote: > On Tue, May 05, 2015 at 06:47:31AM -0700, Andy Lutomirski wrote: > > On Mon, May 4, 2015 at 3:33 AM, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > > > On 29/04/15 22:18, Luis R. Rodriguez wrote: > > >> On Tue, Apr 21, 2015 at 1:16 PM, Luis R. Rodriguez > > >> <mcgrof@xxxxxxxxxxxxxxxx> wrote: > > >>> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx> > > >>> > > >>> This series addresses simple changes to framebuffer drivers to use > > >>> arch_phys_wc_add() and ioremap_wc() as well as fixing gbefb to add > > >>> missing mtrr_del() calls. These changes are pretty straight forward. > > >>> > > >>> Luis R. Rodriguez (17): > > >>> video: fbdev: radeonfb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: gbefb: add missing mtrr_del() calls > > >>> video: fbdev: gbefb: use arch_phys_wc_add() and devm_ioremap_wc() > > >>> video: fbdev: intelfb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: matrox: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: neofb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: nvidia: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: savagefb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: sisfb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: aty: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: i810: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: pm2fb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: pm3fb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: rivafb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: tdfxfb: use arch_phys_wc_add() and ioremap_wc() > > >>> video: fbdev: atmel_lcdfb: use ioremap_wc() for framebuffer > > >>> video: fbdev: geode gxfb: use ioremap_wc() for framebuffer > > >> > > >> Hey folks, these are all pretty straight forward, can anyone take them? > > > > > > I can take these to fbdev tree. Unfortunately I'm not familiar with x86 > > > nor mtrr, so I can't really say much about the patches themselves. > > > > > > > I'm on vacation and there's no way I'll be able to usefully review > > these in the next two weeks. I can describe what's going on in case > > it helps: > > > > On x86 there are two ways to get a write-combining MMIO mapping. The > > sane way is ioremap_wc, and the ridiculous way is mtrr_add. > > ioremap_wc does exactly what it appears to do, whereas mtrr_add acts > > on physical addresses, requires power-of-two alignment, and is > > unreliable. > > > > On all recent hardware, ioremap_wc works, and mtrr_add is problematic > > on all hardware even if it often works. The silly thing is that > > mtrr_add pokes at the registers it uses even on hardware with working > > ioremap_wc. This causes problems (those resources are a very limited > > resource). > > > > The solution I came up with a couple years ago is a new API > > arch_phys_wc_add. It is a hint that a physical address range should > > be write-combining. On hardware with working ioremap_wc, it's a > > no-op. On x86 hardware without working ioremap_wc, it just calls > > mtrr_add. > > > > The upshot is that changing mtrr_add with a WC type to > > arch_phys_wc_add is OK as long as the driver also uses ioremap_wc or > > similar _wc APIs. Once everything has been converted, we can unexport > > mtrr_add, which will have all kinds of benefits. > > Tomi, > > Any chance you can consider this series again? I realize you say you are > not familiar with MTRR but given its prevalence use on framebuffer device > drivers and since you are a framebuffer subsystem maintainer I think its > perhaps fair to ask one of you become familiar with this stuff, or ask > questions if there are any. If its of any help this patch which adds > ioremap_uc() already got merged and the logic to phase MTRR is described > there too: > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=e4b6be33c28923d8cde53023e0888b1c5d1a9027 > > That patch won't even be needed on this series, this series happens to be > straight forward: if you just ioremap_nocache() once and use mtrr_add() > then conver over to ioremap_wc() and use arch_phys_wc_add(). If it already > used ioremap_wc() just convert over from mtrr_add() to arch_phys_wc_add() > > Not sure if you will get an Acked-by by x86 folks on this series as they > are busy, but I'm adding bp and hpa just in case. Hey folks please let me know how I can be of any help with this. Not sure what else I can do here to help further. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
