| Message ID | 574B0302.3010809@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Ivo, On Sun, May 29, 2016 at 05:56:02PM +0300, Ivaylo Dimitrov wrote: >Hi, > >When trying to declare and use DT reserved memory region on ARM >(OMAP3), dma_declare_coherent_memory() fails in memremap(). This is >from today's master: > >------------[ cut here ]------------ >WARNING: CPU: 0 PID: 1 at kernel/memremap.c:111 memremap+0x118/0x194 >memremap attempted on ram 0x8f800000 size: 0x700000 >Modules linked in: >CPU: 0 PID: 1 Comm: swapper Not tainted 4.6.0+ #15 >Hardware name: Nokia RX-51 board >[<c010bc30>] (unwind_backtrace) from [<c0109f70>] (show_stack+0x10/0x14) >[<c0109f70>] (show_stack) from [<c0126d80>] (__warn+0xcc/0xf8) >[<c0126d80>] (__warn) from [<c0126e40>] (warn_slowpath_fmt+0x34/0x44) >[<c0126e40>] (warn_slowpath_fmt) from [<c019c8d4>] (memremap+0x118/0x194) >[<c019c8d4>] (memremap) from [<c03b88fc>] >(dma_init_coherent_memory+0x48/0x104) >[<c03b88fc>] (dma_init_coherent_memory) from [<c03b89e4>] >(dma_declare_coherent_memory+0x2c/0x68) >[<c03b89e4>] (dma_declare_coherent_memory) from [<c0115c0c>] >(rmem_omapfb_device_init+0x34/0x64) >[<c0115c0c>] (rmem_omapfb_device_init) from [<c045b0f8>] >(of_reserved_mem_device_init+0x94/0xd8) >[<c045b0f8>] (of_reserved_mem_device_init) from [<c080aaf8>] >(omapdss_init_of+0xe4/0x154) >[<c080aaf8>] (omapdss_init_of) from [<c08033f4>] >(customize_machine+0x20/0x44) >[<c08033f4>] (customize_machine) from [<c01016b8>] >(do_one_initcall+0xac/0x158) >[<c01016b8>] (do_one_initcall) from [<c0800d64>] >(kernel_init_freeable+0xf8/0x1c8) >[<c0800d64>] (kernel_init_freeable) from [<c05519dc>] >(kernel_init+0x8/0x110) >[<c05519dc>] (kernel_init) from [<c0107258>] (ret_from_fork+0x14/0x3c) >---[ end trace 73a8c076df72166b ]--- >omapfb: dma_declare_coherent_memory failed > > >The failing code looks like: >. >. >. >static int rmem_omapfb_device_init(struct reserved_mem *rmem, struct >device *dev) >{ > int dma; > > if (rmem->priv) > return 0; > > dma = dma_declare_coherent_memory(&omap_fb_device.dev, rmem->base, > rmem->base, rmem->size, > DMA_MEMORY_MAP | > DMA_MEMORY_EXCLUSIVE); > if (!(dma & DMA_MEMORY_MAP)) { > pr_err("omapfb: dma_declare_coherent_memory failed\n"); > return -ENOMEM; > } > else > rmem->priv = omap_fb_device.dev.dma_mem; > > return 0; >} > >static void rmem_omapfb_device_release(struct reserved_mem *rmem, > struct device *dev) >{ > dma_release_declared_memory(&omap_fb_device.dev); >} > >static const struct reserved_mem_ops rmem_omapfb_ops = { > .device_init = rmem_omapfb_device_init, > .device_release = rmem_omapfb_device_release, >}; > >static int __init rmem_omapfb_setup(struct reserved_mem *rmem) >{ > rmem->ops = &rmem_omapfb_ops; > pr_info("omapfb: reserved %d bytes at %pa\n", rmem->size, &rmem->base); > > return 0; >} > >RESERVEDMEM_OF_DECLARE(dss, "ti,omapfb-memsize", rmem_omapfb_setup); > > >It turns out that dma_init_coherent_memory calls memremap with >MEMREMAP_WC flag, which is disallowed for RAM IIUC. > Right. If you want to use a memory region as coherent DMA memory, then that same region can't be System RAM, because System RAM is usually mapped in a non-coherent fashion. >I quickly hacked some code to fix the issue, but as memremap API is >relatively new(esp to me), I wonder if this is the correct way to go: > >diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c >index bdf28f7..04b1687 100644 >--- a/drivers/base/dma-coherent.c >+++ b/drivers/base/dma-coherent.c >@@ -5,6 +5,7 @@ > #include <linux/io.h> > #include <linux/slab.h> > #include <linux/kernel.h> >+#include <linux/memblock.h> > #include <linux/module.h> > #include <linux/dma-mapping.h> > >@@ -32,8 +33,12 @@ static bool dma_init_coherent_memory( > if (!size) > goto out; > >- if (flags & DMA_MEMORY_MAP) >- mem_base = memremap(phys_addr, size, MEMREMAP_WC); >+ if (flags & DMA_MEMORY_MAP) { >+ unsigned long map_type = memblock_is_map_memory(phys_addr) ? >+ MEMREMAP_WB : MEMREMAP_WC; >+ >+ mem_base = memremap(phys_addr, size, map_type); >+ } > else > mem_base = ioremap(phys_addr, size); > if (!mem_base) > >Does the above code looks sane? How to fix the problem if not? AFAIK dma_declare_coherent_memory() should only be used on physical addresses which don't already have a CPU virtual mapping. Certainly returning (potentially) cached memory as DMA coherent is asking for trouble. I think what you want to do is add a "no-map;" property to your reserved-memory region in DT. That will stop the kernel from using it as System RAM, leaving it free for your framebuffer. Cheers, -Brian > >Thanks, >Ivo > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, On 1.06.2016 14:18, Brian Starkey wrote: > Hi Ivo, > > On Sun, May 29, 2016 at 05:56:02PM +0300, Ivaylo Dimitrov wrote: >> Hi, >> >> When trying to declare and use DT reserved memory region on ARM >> (OMAP3), dma_declare_coherent_memory() fails in memremap(). This is >> from today's master: >> >> ------------[ cut here ]------------ >> WARNING: CPU: 0 PID: 1 at kernel/memremap.c:111 memremap+0x118/0x194 >> memremap attempted on ram 0x8f800000 size: 0x700000 >> Modules linked in: >> CPU: 0 PID: 1 Comm: swapper Not tainted 4.6.0+ #15 >> Hardware name: Nokia RX-51 board >> [<c010bc30>] (unwind_backtrace) from [<c0109f70>] (show_stack+0x10/0x14) >> [<c0109f70>] (show_stack) from [<c0126d80>] (__warn+0xcc/0xf8) >> [<c0126d80>] (__warn) from [<c0126e40>] (warn_slowpath_fmt+0x34/0x44) >> [<c0126e40>] (warn_slowpath_fmt) from [<c019c8d4>] (memremap+0x118/0x194) >> [<c019c8d4>] (memremap) from [<c03b88fc>] >> (dma_init_coherent_memory+0x48/0x104) >> [<c03b88fc>] (dma_init_coherent_memory) from [<c03b89e4>] >> (dma_declare_coherent_memory+0x2c/0x68) >> [<c03b89e4>] (dma_declare_coherent_memory) from [<c0115c0c>] >> (rmem_omapfb_device_init+0x34/0x64) >> [<c0115c0c>] (rmem_omapfb_device_init) from [<c045b0f8>] >> (of_reserved_mem_device_init+0x94/0xd8) >> [<c045b0f8>] (of_reserved_mem_device_init) from [<c080aaf8>] >> (omapdss_init_of+0xe4/0x154) >> [<c080aaf8>] (omapdss_init_of) from [<c08033f4>] >> (customize_machine+0x20/0x44) >> [<c08033f4>] (customize_machine) from [<c01016b8>] >> (do_one_initcall+0xac/0x158) >> [<c01016b8>] (do_one_initcall) from [<c0800d64>] >> (kernel_init_freeable+0xf8/0x1c8) >> [<c0800d64>] (kernel_init_freeable) from [<c05519dc>] >> (kernel_init+0x8/0x110) >> [<c05519dc>] (kernel_init) from [<c0107258>] (ret_from_fork+0x14/0x3c) >> ---[ end trace 73a8c076df72166b ]--- >> omapfb: dma_declare_coherent_memory failed >> >> >> The failing code looks like: >> . >> . >> . >> static int rmem_omapfb_device_init(struct reserved_mem *rmem, struct >> device *dev) >> { >> int dma; >> >> if (rmem->priv) >> return 0; >> >> dma = dma_declare_coherent_memory(&omap_fb_device.dev, rmem->base, >> rmem->base, rmem->size, >> DMA_MEMORY_MAP | >> DMA_MEMORY_EXCLUSIVE); >> if (!(dma & DMA_MEMORY_MAP)) { >> pr_err("omapfb: dma_declare_coherent_memory failed\n"); >> return -ENOMEM; >> } >> else >> rmem->priv = omap_fb_device.dev.dma_mem; >> >> return 0; >> } >> >> static void rmem_omapfb_device_release(struct reserved_mem *rmem, >> struct device *dev) >> { >> dma_release_declared_memory(&omap_fb_device.dev); >> } >> >> static const struct reserved_mem_ops rmem_omapfb_ops = { >> .device_init = rmem_omapfb_device_init, >> .device_release = rmem_omapfb_device_release, >> }; >> >> static int __init rmem_omapfb_setup(struct reserved_mem *rmem) >> { >> rmem->ops = &rmem_omapfb_ops; >> pr_info("omapfb: reserved %d bytes at %pa\n", rmem->size, >> &rmem->base); >> >> return 0; >> } >> >> RESERVEDMEM_OF_DECLARE(dss, "ti,omapfb-memsize", rmem_omapfb_setup); >> >> >> It turns out that dma_init_coherent_memory calls memremap with >> MEMREMAP_WC flag, which is disallowed for RAM IIUC. >> > > Right. If you want to use a memory region as coherent DMA memory, then > that same region can't be System RAM, because System RAM is usually > mapped in a non-coherent fashion. > >> I quickly hacked some code to fix the issue, but as memremap API is >> relatively new(esp to me), I wonder if this is the correct way to go: >> >> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c >> index bdf28f7..04b1687 100644 >> --- a/drivers/base/dma-coherent.c >> +++ b/drivers/base/dma-coherent.c >> @@ -5,6 +5,7 @@ >> #include <linux/io.h> >> #include <linux/slab.h> >> #include <linux/kernel.h> >> +#include <linux/memblock.h> >> #include <linux/module.h> >> #include <linux/dma-mapping.h> >> >> @@ -32,8 +33,12 @@ static bool dma_init_coherent_memory( >> if (!size) >> goto out; >> >> - if (flags & DMA_MEMORY_MAP) >> - mem_base = memremap(phys_addr, size, MEMREMAP_WC); >> + if (flags & DMA_MEMORY_MAP) { >> + unsigned long map_type = >> memblock_is_map_memory(phys_addr) ? >> + MEMREMAP_WB : >> MEMREMAP_WC; >> + >> + mem_base = memremap(phys_addr, size, map_type); >> + } >> else >> mem_base = ioremap(phys_addr, size); >> if (!mem_base) >> >> Does the above code looks sane? How to fix the problem if not? > > AFAIK dma_declare_coherent_memory() should only be used on physical > addresses which don't already have a CPU virtual mapping. Certainly > returning (potentially) cached memory as DMA coherent is asking for > trouble. > > I think what you want to do is add a "no-map;" property to your > reserved-memory region in DT. That will stop the kernel from using it > as System RAM, leaving it free for your framebuffer. > I tried to use "no-map", but for some reason it doesn't allow me to allocate more than 2MB, anything above results in: qemu: fatal: Trying to execute code outside RAM or ROM at 0xffff0010 R00=22222220 R01=cf901000 R02=cfaffff4 R03=e0000000 R04=0008ff80 R05=00090000 R06=00000000 R07=c096333c R08=c0904dc0 R09=c093a23c R10=00000001 R11=c0727b3b R12=0000ff80 R13=c093af8c R14=c082aba0 R15=ffff0010 PSR=a00001d7 N-C- A abt32 Aborted (core dumped) I was able to track the code to memblock_isolate_range() - if I return -ENOMEM on http://lxr.free-electrons.com/source/mm/memblock.c#L671, the above crash does not occur(however the allocation fails as well). Putting some printks doesn't reveal anything suspicious to me: for 2MB: [ 0.000000] base 8fe00000, size 200000, rgn->base 80000000, rgn->size 10000000, type->total_size 10000000 [ 0.000000] base - rbase fe00000 for 4MB: [ 0.000000] base 8fc00000, size 400000, rgn->base 80000000, rgn->size 10000000, type->total_size 10000000 [ 0.000000] base - rbase fc00000 However, this is where my limited memblock knowledge ends, so any help is appreciated. Maybe I should CC memblock authors as well? Thanks, Ivo -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2.06.2016 20:14, Ivaylo Dimitrov wrote: > Hi, > > On 1.06.2016 14:18, Brian Starkey wrote: >> Hi Ivo, >> >> On Sun, May 29, 2016 at 05:56:02PM +0300, Ivaylo Dimitrov wrote: >>> Hi, >>> >>> When trying to declare and use DT reserved memory region on ARM >>> (OMAP3), dma_declare_coherent_memory() fails in memremap(). This is >>> from today's master: >>> >>> ------------[ cut here ]------------ >>> WARNING: CPU: 0 PID: 1 at kernel/memremap.c:111 memremap+0x118/0x194 >>> memremap attempted on ram 0x8f800000 size: 0x700000 >>> Modules linked in: >>> CPU: 0 PID: 1 Comm: swapper Not tainted 4.6.0+ #15 >>> Hardware name: Nokia RX-51 board >>> [<c010bc30>] (unwind_backtrace) from [<c0109f70>] (show_stack+0x10/0x14) >>> [<c0109f70>] (show_stack) from [<c0126d80>] (__warn+0xcc/0xf8) >>> [<c0126d80>] (__warn) from [<c0126e40>] (warn_slowpath_fmt+0x34/0x44) >>> [<c0126e40>] (warn_slowpath_fmt) from [<c019c8d4>] >>> (memremap+0x118/0x194) >>> [<c019c8d4>] (memremap) from [<c03b88fc>] >>> (dma_init_coherent_memory+0x48/0x104) >>> [<c03b88fc>] (dma_init_coherent_memory) from [<c03b89e4>] >>> (dma_declare_coherent_memory+0x2c/0x68) >>> [<c03b89e4>] (dma_declare_coherent_memory) from [<c0115c0c>] >>> (rmem_omapfb_device_init+0x34/0x64) >>> [<c0115c0c>] (rmem_omapfb_device_init) from [<c045b0f8>] >>> (of_reserved_mem_device_init+0x94/0xd8) >>> [<c045b0f8>] (of_reserved_mem_device_init) from [<c080aaf8>] >>> (omapdss_init_of+0xe4/0x154) >>> [<c080aaf8>] (omapdss_init_of) from [<c08033f4>] >>> (customize_machine+0x20/0x44) >>> [<c08033f4>] (customize_machine) from [<c01016b8>] >>> (do_one_initcall+0xac/0x158) >>> [<c01016b8>] (do_one_initcall) from [<c0800d64>] >>> (kernel_init_freeable+0xf8/0x1c8) >>> [<c0800d64>] (kernel_init_freeable) from [<c05519dc>] >>> (kernel_init+0x8/0x110) >>> [<c05519dc>] (kernel_init) from [<c0107258>] (ret_from_fork+0x14/0x3c) >>> ---[ end trace 73a8c076df72166b ]--- >>> omapfb: dma_declare_coherent_memory failed >>> >>> >>> The failing code looks like: >>> . >>> . >>> . >>> static int rmem_omapfb_device_init(struct reserved_mem *rmem, struct >>> device *dev) >>> { >>> int dma; >>> >>> if (rmem->priv) >>> return 0; >>> >>> dma = dma_declare_coherent_memory(&omap_fb_device.dev, rmem->base, >>> rmem->base, rmem->size, >>> DMA_MEMORY_MAP | >>> DMA_MEMORY_EXCLUSIVE); >>> if (!(dma & DMA_MEMORY_MAP)) { >>> pr_err("omapfb: dma_declare_coherent_memory failed\n"); >>> return -ENOMEM; >>> } >>> else >>> rmem->priv = omap_fb_device.dev.dma_mem; >>> >>> return 0; >>> } >>> >>> static void rmem_omapfb_device_release(struct reserved_mem *rmem, >>> struct device *dev) >>> { >>> dma_release_declared_memory(&omap_fb_device.dev); >>> } >>> >>> static const struct reserved_mem_ops rmem_omapfb_ops = { >>> .device_init = rmem_omapfb_device_init, >>> .device_release = rmem_omapfb_device_release, >>> }; >>> >>> static int __init rmem_omapfb_setup(struct reserved_mem *rmem) >>> { >>> rmem->ops = &rmem_omapfb_ops; >>> pr_info("omapfb: reserved %d bytes at %pa\n", rmem->size, >>> &rmem->base); >>> >>> return 0; >>> } >>> >>> RESERVEDMEM_OF_DECLARE(dss, "ti,omapfb-memsize", rmem_omapfb_setup); >>> >>> >>> It turns out that dma_init_coherent_memory calls memremap with >>> MEMREMAP_WC flag, which is disallowed for RAM IIUC. >>> >> >> Right. If you want to use a memory region as coherent DMA memory, then >> that same region can't be System RAM, because System RAM is usually >> mapped in a non-coherent fashion. >> >>> I quickly hacked some code to fix the issue, but as memremap API is >>> relatively new(esp to me), I wonder if this is the correct way to go: >>> >>> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c >>> index bdf28f7..04b1687 100644 >>> --- a/drivers/base/dma-coherent.c >>> +++ b/drivers/base/dma-coherent.c >>> @@ -5,6 +5,7 @@ >>> #include <linux/io.h> >>> #include <linux/slab.h> >>> #include <linux/kernel.h> >>> +#include <linux/memblock.h> >>> #include <linux/module.h> >>> #include <linux/dma-mapping.h> >>> >>> @@ -32,8 +33,12 @@ static bool dma_init_coherent_memory( >>> if (!size) >>> goto out; >>> >>> - if (flags & DMA_MEMORY_MAP) >>> - mem_base = memremap(phys_addr, size, MEMREMAP_WC); >>> + if (flags & DMA_MEMORY_MAP) { >>> + unsigned long map_type = >>> memblock_is_map_memory(phys_addr) ? >>> + MEMREMAP_WB : >>> MEMREMAP_WC; >>> + >>> + mem_base = memremap(phys_addr, size, map_type); >>> + } >>> else >>> mem_base = ioremap(phys_addr, size); >>> if (!mem_base) >>> >>> Does the above code looks sane? How to fix the problem if not? >> >> AFAIK dma_declare_coherent_memory() should only be used on physical >> addresses which don't already have a CPU virtual mapping. Certainly >> returning (potentially) cached memory as DMA coherent is asking for >> trouble. >> >> I think what you want to do is add a "no-map;" property to your >> reserved-memory region in DT. That will stop the kernel from using it >> as System RAM, leaving it free for your framebuffer. >> > > I tried to use "no-map", but for some reason it doesn't allow me to > allocate more than 2MB, anything above results in: > > qemu: fatal: Trying to execute code outside RAM or ROM at 0xffff0010 > > R00=22222220 R01=cf901000 R02=cfaffff4 R03=e0000000 > R04=0008ff80 R05=00090000 R06=00000000 R07=c096333c > R08=c0904dc0 R09=c093a23c R10=00000001 R11=c0727b3b > R12=0000ff80 R13=c093af8c R14=c082aba0 R15=ffff0010 > PSR=a00001d7 N-C- A abt32 > Aborted (core dumped) > > I was able to track the code to memblock_isolate_range() - if I return > -ENOMEM on http://lxr.free-electrons.com/source/mm/memblock.c#L671, the > above crash does not occur(however the allocation fails as well). > Putting some printks doesn't reveal anything suspicious to me: > > for 2MB: > > [ 0.000000] base 8fe00000, size 200000, rgn->base 80000000, rgn->size > 10000000, type->total_size 10000000 > [ 0.000000] base - rbase fe00000 > > > for 4MB: > > [ 0.000000] base 8fc00000, size 400000, rgn->base 80000000, rgn->size > 10000000, type->total_size 10000000 > [ 0.000000] base - rbase fc00000 > > > However, this is where my limited memblock knowledge ends, so any help > is appreciated. > It turned out I have to increase CONFIG_FORCE_MAX_ZONEORDER in order to be able to use more than 2MB of allocated memory. Ivo -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c index bdf28f7..04b1687 100644 --- a/drivers/base/dma-coherent.c +++ b/drivers/base/dma-coherent.c @@ -5,6 +5,7 @@ #include <linux/io.h> #include <linux/slab.h> #include <linux/kernel.h> +#include <linux/memblock.h> #include <linux/module.h> #include <linux/dma-mapping.h> @@ -32,8 +33,12 @@ static bool dma_init_coherent_memory( if (!size) goto out; - if (flags & DMA_MEMORY_MAP) - mem_base = memremap(phys_addr, size, MEMREMAP_WC); + if (flags & DMA_MEMORY_MAP) { + unsigned long map_type = memblock_is_map_memory(phys_addr) ? + MEMREMAP_WB : MEMREMAP_WC; + + mem_base = memremap(phys_addr, size, map_type); + } else mem_base = ioremap(phys_addr, size); if (!mem_base)
Hi, When trying to declare and use DT reserved memory region on ARM (OMAP3), dma_declare_coherent_memory() fails in memremap(). This is from today's master: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1 at kernel/memremap.c:111 memremap+0x118/0x194 memremap attempted on ram 0x8f800000 size: 0x700000 Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 4.6.0+ #15 Hardware name: Nokia RX-51 board [<c010bc30>] (unwind_backtrace) from [<c0109f70>] (show_stack+0x10/0x14) [<c0109f70>] (show_stack) from [<c0126d80>] (__warn+0xcc/0xf8) [<c0126d80>] (__warn) from [<c0126e40>] (warn_slowpath_fmt+0x34/0x44) [<c0126e40>] (warn_slowpath_fmt) from [<c019c8d4>] (memremap+0x118/0x194) [<c019c8d4>] (memremap) from [<c03b88fc>] (dma_init_coherent_memory+0x48/0x104) [<c03b88fc>] (dma_init_coherent_memory) from [<c03b89e4>] (dma_declare_coherent_memory+0x2c/0x68) [<c03b89e4>] (dma_declare_coherent_memory) from [<c0115c0c>] (rmem_omapfb_device_init+0x34/0x64) [<c0115c0c>] (rmem_omapfb_device_init) from [<c045b0f8>] (of_reserved_mem_device_init+0x94/0xd8) [<c045b0f8>] (of_reserved_mem_device_init) from [<c080aaf8>] (omapdss_init_of+0xe4/0x154) [<c080aaf8>] (omapdss_init_of) from [<c08033f4>] (customize_machine+0x20/0x44) [<c08033f4>] (customize_machine) from [<c01016b8>] (do_one_initcall+0xac/0x158) [<c01016b8>] (do_one_initcall) from [<c0800d64>] (kernel_init_freeable+0xf8/0x1c8) [<c0800d64>] (kernel_init_freeable) from [<c05519dc>] (kernel_init+0x8/0x110) [<c05519dc>] (kernel_init) from [<c0107258>] (ret_from_fork+0x14/0x3c) ---[ end trace 73a8c076df72166b ]--- omapfb: dma_declare_coherent_memory failed The failing code looks like: . . . static int rmem_omapfb_device_init(struct reserved_mem *rmem, struct device *dev) { int dma; if (rmem->priv) return 0; dma = dma_declare_coherent_memory(&omap_fb_device.dev, rmem->base, rmem->base, rmem->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE); if (!(dma & DMA_MEMORY_MAP)) { pr_err("omapfb: dma_declare_coherent_memory failed\n"); return -ENOMEM; } else rmem->priv = omap_fb_device.dev.dma_mem; return 0; } static void rmem_omapfb_device_release(struct reserved_mem *rmem, struct device *dev) { dma_release_declared_memory(&omap_fb_device.dev); } static const struct reserved_mem_ops rmem_omapfb_ops = { .device_init = rmem_omapfb_device_init, .device_release = rmem_omapfb_device_release, }; static int __init rmem_omapfb_setup(struct reserved_mem *rmem) { rmem->ops = &rmem_omapfb_ops; pr_info("omapfb: reserved %d bytes at %pa\n", rmem->size, &rmem->base); return 0; } RESERVEDMEM_OF_DECLARE(dss, "ti,omapfb-memsize", rmem_omapfb_setup); It turns out that dma_init_coherent_memory calls memremap with MEMREMAP_WC flag, which is disallowed for RAM IIUC. I quickly hacked some code to fix the issue, but as memremap API is relatively new(esp to me), I wonder if this is the correct way to go: Does the above code looks sane? How to fix the problem if not? Thanks, Ivo -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html