On 7/27/2024 1:56 AM, Krzysztof Kozlowski wrote:
On 27/07/2024 00:59, Roman Kisel wrote:
@@ -2338,6 +2372,21 @@ static int vmbus_device_add(struct platform_device *pdev)
cur_res = &res->sibling;
}
+ /*
+ * Hyper-V always assumes DMA cache coherency, and the DMA subsystem
+ * might default to 'not coherent' on some architectures.
+ * Avoid high-cost cache coherency maintenance done by the CPU.
+ */
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
+ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
+ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
+
+ if (!of_property_read_bool(np, "dma-coherent"))
+ pr_warn("Assuming cache coherent DMA transactions, no 'dma-coherent' node supplied\n");
Why do you need this property at all, if it is allways dma-coherent? Are
you supporting dma-noncoherent somewhere?
No support for non-coherent. Wanted to do a sanity check. Had better
check for dma-noncoherent and warn about that I believe.
Best regards,
Krzysztof
--
Thank you,
Roman
