Hi,
On 2023/6/1 00:23, Lucas Stach wrote:
Hi Sui Jingfeng,
Am Donnerstag, dem 01.06.2023 um 00:08 +0800 schrieb Sui Jingfeng:
Hi,
On 2023/5/31 03:02, Bjorn Helgaas wrote:
On Wed, May 31, 2023 at 12:06:42AM +0800, Sui Jingfeng wrote:
This patch adds PCI driver support on top of what already have. Take the
GC1000 in LS7A1000/LS2K1000 as the first instance of the PCI device driver.
There is only one GPU core for the GC1000 in the LS7A1000 and LS2K1000.
Therefore, component frameworks can be avoided. Because we want to bind the
DRM driver service to the PCI driver manually.
+ * Loongson Mips and LoongArch CPU(ls3a5000, ls3a4000, ls2k1000la)
+ * maintain cache coherency by hardware
+ */
+ if (IS_ENABLED(CONFIG_CPU_LOONGSON64) || IS_ENABLED(CONFIG_LOONGARCH))
+ priv->has_cached_coherent = true;
This looks like something that should be a runtime check, not a
compile-time check.
If it's possible to build a single kernel image that runs on Loongson
MIPS or LoongArch CPU and, in addition, runs on other platforms, you
cannot assume that all the others maintain this cache coherency.
Nice catch! I don't even realize this!
LS3A4000 is mips64r2 with MSA SIMD, while LS3A5000 is LoongArch,
instruction set, compiler, and binary interface are totally changed.
Therefore, it's impossible to build a single kernel image that runs on
all Loongson CPUs.
Currently, I can guarantee that this works on the Loongson platform.
My initial intent here is to let priv->has_cached_coherent be *true* on
the Loongson platform (both mips and loongarch).
I do know there are some other vendors who bought GPU IP from Vivante.
say GC7000, and integrate it into their discrete GPU product.
But it is also a PCI device, but this is another story; it deserves
another patch.
I don't know if Etnaviv folk find some similar hardware on Arm Arch,
Some Arm CPUs do not maintain cached coherency on hardware.
The has_cached_coherent member can be set to false on such hardware.
For us, it seems that there is no need to do runtime checking,
because they are all cached coherent by default.
Can I improve this in the future, currently I don't have a good idea.
I think I mentioned before that this needs to be a runtime check. What
does dev_is_dma_coherent() return for the Vivante GPU device on your
platform?
Yes, you have told me so.
I will try it, and I will answer your question tomorrow.
Regards,
Lucas
--
Jingfeng
