Hi,
On 2023/6/22 00:12, Lucas Stach wrote:
Am Mittwoch, dem 21.06.2023 um 23:41 +0800 schrieb Sui Jingfeng:
On 2023/6/21 23:23, Lucas Stach wrote:
Am Mittwoch, dem 21.06.2023 um 22:44 +0800 schrieb Sui Jingfeng:
Hi,
On 2023/6/21 18:00, Lucas Stach wrote:
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.h b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
index 9cd72948cfad..644e5712c050 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_drv.h
+++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
@@ -46,6 +46,12 @@ struct etnaviv_drm_private {
struct xarray active_contexts;
u32 next_context_id;
+ /*
+ * If true, the GPU is capable of snooping cpu cache. Here, it
+ * also means that cache coherency is enforced by the hardware.
+ */
+ bool dma_coherent;
+
No need for this, I think. Just use dev_is_dma_coherent() where you
need to know this.
No, we want this value cached by the driver.
Why? dev_is_dma_coherent() is a header-only function with a single
pointer chasing operation. Your cache is also a single pointer chasing
access, just that we now need storage for this information in both
struct device and struct etnaviv_gpu.
You don't need store it in struct etnaviv_gpu.
As this variable is shared across the device, so it is better to be put
in the struct etnaviv_drm_private.
I don't think another 4 bytes allocation is something what we can't pay for.
My patch doesn't mentioned that it need to store it inside of struct
etnaviv_gpu, do I?
You are right, I was mistaken about the etnaviv struct this is added
to. However there is still the fundamental question: what's the gain of
this cache? The information is already available in struct device and
will be accessed with the same amount of loads if you care that much
about micro-optimization.
Sometime, in some function it is more convenient(easier) to fetch
'struct etnaviv_drm_private *priv'
than the 'struct device *dev', I think this is obvious.
Regards,
Lucas
--
Jingfeng
