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From: Saravana Kannan <saravanak@xxxxxxxxxx>
Sent: Wednesday, September 7, 2022 5:41 AM
To: Gupta, Nipun <Nipun.Gupta@xxxxxxx>
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Subject: Re: [RFC PATCH v3 3/7] iommu/arm-smmu-v3: support ops registration
for CDX bus
[CAUTION: External Email]
On Tue, Sep 6, 2022 at 6:48 AM Nipun Gupta <nipun.gupta@xxxxxxx> wrote:
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
With new CDX bus supported for AMD FPGA devices on ARM
platform, the bus requires registration for the SMMU v3
driver.
Signed-off-by: Nipun Gupta <nipun.gupta@xxxxxxx>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index d32b02336411..8ec9f2baf12d 100644iommu_ops *ops)
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -29,6 +29,7 @@
#include <linux/platform_device.h>
#include <linux/amba/bus.h>
+#include <linux/cdx/cdx_bus.h>
#include "arm-smmu-v3.h"
#include "../../iommu-sva-lib.h"
@@ -3690,16 +3691,27 @@ static int arm_smmu_set_bus_ops(struct
if (err)
goto err_reset_pci_ops;
}
+#endif
+#ifdef CONFIG_CDX_BUS
+ if (cdx_bus_type.iommu_ops != ops) {
+ err = bus_set_iommu(&cdx_bus_type, ops);
+ if (err)
+ goto err_reset_amba_ops;
+ }
I'm not an expert on IOMMUs, so apologies if the question is stupid.
Why does the CDX bus need special treatment here (like PCI) when there
are so many other busses (eg: I2C, SPI, etc) that don't need any
changes here?
AFAIU, the devices on I2C/SPI does not use SMMU. Apart from PCI/AMBA,
FSL-MC is another similar bus (on SMMUv2) which uses SMMU ops.
The devices here are behind SMMU. Robin can kindly correct or add
more here from SMMU perspective.
Thanks,
Nipun
-Saravana
#endif
if (platform_bus_type.iommu_ops != ops) {
err = bus_set_iommu(&platform_bus_type, ops);
if (err)
- goto err_reset_amba_ops;
+ goto err_reset_cdx_ops;
}
return 0;
-err_reset_amba_ops:
+err_reset_cdx_ops:
+#ifdef CONFIG_CDX_BUS
+ bus_set_iommu(&cdx_bus_type, NULL);
+#endif
+err_reset_amba_ops: __maybe_unused;
#ifdef CONFIG_ARM_AMBA
bus_set_iommu(&amba_bustype, NULL);
#endif
--
2.25.1