>________________________________________ >From: FUJITA Tomonori [fujita.tomonori@xxxxxxxxxxxxx] >Sent: Thursday, August 26, 2010 7:56 AM >To: Guzman Lugo, Fernando >Cc: fujita.tomonori@xxxxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; ohad@xxxxxxxxxx; hiroshi.doyu@xxxxxxxxx; ameya.palande@xxxxxxxxx; >felipe.contreras@xxxxxxxxx >Subject: RE: [PATCH 8/9] dspbridge: add map support for big buffers > >On Thu, 26 Aug 2010 07:38:26 -0500 >"Guzman Lugo, Fernando" <fernando.lugo@xxxxxx> wrote: > >> >> due to a restriction in scatter gather lists, it can >> >> not be created a list for a buffer bigger than 1MB. >> >> This patch is spliting big mappings into 1MB mappings. >> > >> >I don't read the whole thread but the above description is incorrect. >> > >> >Why can't you use scatter gather chaining? You can create a scatter >> >list for a buffer larger than 1MB. >> >> The thing is that ARM architecture does not support SG chaining. This patch should be >> seen like a workaround until it is fixed in iovmm module. > >Fix iovmm module is easier than the workaround? I have not thought about possible fixes inside iovmm, but now I am reviewing the patches I will figure out how to fix this inside iovmm. Since he workaround still can fail to allocate big buffers even though there is space to allocate it. > >From a quick look, arch/arm/plat-omap/iovmm.c does nothing wrong about >scatter gather chaining. arm/arm/mm/dma-mapping.c looks fine too about >it. Maybe just defining ARCH_HAS_SG_CHAIN works? I can try, but it looks tricky for me. Maybe someone else can tell us why SG chain is not supported for ARM or if there is a problem just defining ARCH_HAS_SG_CHAIN. Regards, Fernando. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
