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<div class="moz-cite-prefix">On 7/24/2023 10:43 PM, Alex Deucher
wrote:<br>
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<blockquote type="cite" cite="mid:CADnq5_NcEr3=bDoSo5_YYYuNAMps655fcOuUDaAPmw3_QDwQNQ@mail.gmail.com">
<pre class="moz-quote-pre" wrap="">On Mon, Jul 24, 2023 at 11:54 AM Srinivasan Shanmugam
<a class="moz-txt-link-rfc2396E" href="mailto:srinivasan.shanmugam@amd.com"><srinivasan.shanmugam@amd.com></a> wrote:
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Fixes the following from checkpatch.pl:
WARNING: Use of volatile is usually wrong: see Documentation/process/volatile-considered-harmful.rst
+ volatile uint32_t *wb;
WARNING: Use of volatile is usually wrong: see Documentation/process/volatile-considered-harmful.rst
+ volatile uint32_t *ptr;
'wb' field from 'amdgpu_wb' struct & 'ptr' field from
'amdgpu_mem_scratch', is not used to access h/w directly, neither they
are shared variables, so volatile is not necessary
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How did you come to that determination? Both are GPU accessible
memory allocations. The writeback (wb) allocation happens to be in
GTT so it's system memory, but the the mem_scratch allocation can be
in device memory.
Alex
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<p>Hi Alex,</p>
<p>Thanks for your feedbacks!<br>
</p>
<p>Commit message is misleading, I presumed that this volatile
modifiers are used for monitoring HW status registers due to
external events & for some shared variables - <span><span class="ui-provider fy b c d e f g h i j k l m n o p q r s t u v w x y z ab ac ae af ag ah ai aj ak" dir="ltr"> may be volatile might be needed for *wb pointer
variable - as they may be used for caches in between (on
surface level info), can we split this patch into two, I felt
volatile for *ptr is unnecessary as it is type casted with
void type [(void **)&adev->mem_scratch.ptr); in
amdgpu_device.c]- Any advises onto this please?</span></span></p>
<p><span><span class="ui-provider fy b c d e f g h i j k l m n o p q r s t u v w x y z ab ac ae af ag ah ai aj ak" dir="ltr">Best regards,</span></span></p>
<p><span><span class="ui-provider fy b c d e f g h i j k l m n o p q r s t u v w x y z ab ac ae af ag ah ai aj ak" dir="ltr">Srini<br>
</span></span></p>
<blockquote type="cite" cite="mid:CADnq5_NcEr3=bDoSo5_YYYuNAMps655fcOuUDaAPmw3_QDwQNQ@mail.gmail.com">
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<pre class="moz-quote-pre" wrap="">
Cc: Christian König <a class="moz-txt-link-rfc2396E" href="mailto:christian.koenig@amd.com"><christian.koenig@amd.com></a>
Cc: Alex Deucher <a class="moz-txt-link-rfc2396E" href="mailto:alexander.deucher@amd.com"><alexander.deucher@amd.com></a>
Signed-off-by: Srinivasan Shanmugam <a class="moz-txt-link-rfc2396E" href="mailto:srinivasan.shanmugam@amd.com"><srinivasan.shanmugam@amd.com></a>
---
drivers/gpu/drm/amd/amdgpu/amdgpu.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index a046160b6a0e..06f79a84ff4b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -502,7 +502,7 @@ int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv);
struct amdgpu_wb {
struct amdgpu_bo *wb_obj;
- volatile uint32_t *wb;
+ u32 *wb;
uint64_t gpu_addr;
u32 num_wb; /* Number of wb slots actually reserved for amdgpu. */
unsigned long used[DIV_ROUND_UP(AMDGPU_MAX_WB, BITS_PER_LONG)];
@@ -621,7 +621,7 @@ int amdgpu_cs_wait_fences_ioctl(struct drm_device *dev, void *data,
/* VRAM scratch page for HDP bug, default vram page */
struct amdgpu_mem_scratch {
struct amdgpu_bo *robj;
- volatile uint32_t *ptr;
+ u32 *ptr;
u64 gpu_addr;
};
--
2.25.1
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