On Sun, Sep 29, 2019 at 03:28:41PM +0800, jun.zhang@intel.com wrote:

From: zhang jun jun.zhang@intel.com

we see tons of warning like: [ 45.846872] x86/PAT: NDK MediaCodec_:3753 map pfn RAM range req write-combining for [mem 0x1e7a80000-0x1e7a87fff], got write-back [ 45.848827] x86/PAT: .vorbis.decoder:4088 map pfn RAM range req write-combining for [mem 0x1e7a58000-0x1e7a58fff], got write-back [ 45.848875] x86/PAT: NDK MediaCodec_:3753 map pfn RAM range req write-combining for [mem 0x1e7a48000-0x1e7a4ffff], got write-back [ 45.849403] x86/PAT: .vorbis.decoder:4088 map pfn RAM range req write-combining for [mem 0x1e7a70000-0x1e7a70fff], got write-back

check the kernel Documentation/x86/pat.txt, it says: A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range, vm_insert_pfn Drivers wanting to export some pages to userspace do it by using mmap interface and a combination of

1. pgprot_noncached()
2. io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn()

With PAT support, a new API pgprot_writecombine is being added. So, drivers can continue to use the above sequence, with either pgprot_noncached() or pgprot_writecombine() in step 1, followed by step 2.

In addition, step 2 internally tracks the region as UC or WC in memtype list in order to ensure no conflicting mapping.

Note that this set of APIs only works with IO (non RAM) regions. If driver ants to export a RAM region, it has to do set_memory_uc() or set_memory_wc() as step 0 above and also track the usage of those pages and use set_memory_wb() before the page is freed to free pool.

the fix follow the pat document, do set_memory_wc() as step 0 and use the set_memory_wb() before the page is freed.

Signed-off-by: he, bo bo.he@intel.com Signed-off-by: zhang jun jun.zhang@intel.com Signed-off-by: Bai, Jie A jie.a.bai@intel.com

---

drivers/staging/android/ion/ion_system_heap.c | 28 ++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index b83a1d16bd89..d298b8194820 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -13,6 +13,7 @@ #include <linux/scatterlist.h> #include <linux/slab.h> #include <linux/vmalloc.h> +#include <asm/set_memory.h> #include "ion.h" @@ -134,6 +135,13 @@ static int ion_system_heap_allocate(struct ion_heap *heap, sg = table->sgl; list_for_each_entry_safe(page, tmp_page, &pages, lru) { sg_set_page(sg, page, page_size(page), 0);

+#ifdef CONFIG_X86

• if (!(buffer->flags & ION_FLAG_CACHED))

• set_memory_wc((unsigned long)page_address(sg_page(sg)),
  

• 	      PAGE_ALIGN(sg->length) >> PAGE_SHIFT);
  

+#endif

There is no way to do this without these #ifdefs? That feels odd, why can't you just always test for this?

thanks,

greg k-h