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Subject[PATCH 2/3] iommu/io-pgtable-arm: Add support to use system cache
Date
Few Qualcomm platforms such as, sdm845 have an additional outer
cache called as System cache, aka. Last level cache (LLC) that
allows non-coherent devices to upgrade to using caching.

There is a fundamental assumption that non-coherent devices can't
access caches. This change adds an exception where they *can* use
some level of cache despite still being non-coherent overall.
The coherent devices that use cacheable memory, and CPU make use of
this system cache by default.

Looking at memory types, we have following -
a) Normal uncached :- MAIR 0x44, inner non-cacheable,
outer non-cacheable;
b) Normal cached :- MAIR 0xff, inner read write-back non-transient,
outer read write-back non-transient;
attribute setting for coherenet I/O devices.
and, for non-coherent i/o devices that can allocate in system cache
another type gets added -
c) Normal sys-cached :- MAIR 0xf4, inner non-cacheable,
outer read write-back non-transient

Coherent I/O devices use system cache by marking the memory as
normal cached.
Non-coherent I/O devices should mark the memory as normal
sys-cached in page tables to use system cache.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
---
drivers/iommu/io-pgtable-arm.c | 15 +++++++++++++--
drivers/iommu/io-pgtable.h | 4 ++++
include/linux/iommu.h | 2 ++
3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index c76919c30f1a..0e55772702da 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -168,10 +168,12 @@
#define ARM_LPAE_MAIR_ATTR_MASK 0xff
#define ARM_LPAE_MAIR_ATTR_DEVICE 0x04
#define ARM_LPAE_MAIR_ATTR_NC 0x44
+#define ARM_LPAE_MAIR_ATTR_QCOM_SYS_CACHE 0xf4
#define ARM_LPAE_MAIR_ATTR_WBRWA 0xff
#define ARM_LPAE_MAIR_ATTR_IDX_NC 0
#define ARM_LPAE_MAIR_ATTR_IDX_CACHE 1
#define ARM_LPAE_MAIR_ATTR_IDX_DEV 2
+#define ARM_LPAE_MAIR_ATTR_IDX_QCOM_SYS_CACHE 3

/* IOPTE accessors */
#define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d))
@@ -443,6 +445,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
else if (prot & IOMMU_CACHE)
pte |= (ARM_LPAE_MAIR_ATTR_IDX_CACHE
<< ARM_LPAE_PTE_ATTRINDX_SHIFT);
+ else if (prot & IOMMU_QCOM_SYS_CACHE)
+ pte |= (ARM_LPAE_MAIR_ATTR_IDX_QCOM_SYS_CACHE
+ << ARM_LPAE_PTE_ATTRINDX_SHIFT);
} else {
pte = ARM_LPAE_PTE_HAP_FAULT;
if (prot & IOMMU_READ)
@@ -781,7 +786,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)

if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS | IO_PGTABLE_QUIRK_NO_DMA |
IO_PGTABLE_QUIRK_NON_STRICT |
- IO_PGTABLE_QUIRK_NON_COHERENT))
+ IO_PGTABLE_QUIRK_NON_COHERENT |
+ IO_PGTABLE_QUIRK_QCOM_SYS_CACHE))
return NULL;

data = arm_lpae_alloc_pgtable(cfg);
@@ -794,6 +800,9 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
if (cfg->quirks & IO_PGTABLE_QUIRK_NON_COHERENT)
reg |= ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_IRGN0_SHIFT |
ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_ORGN0_SHIFT;
+ else if (cfg->quirks & IO_PGTABLE_QUIRK_QCOM_SYS_CACHE)
+ reg |= ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_IRGN0_SHIFT |
+ ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT;
else
reg |= ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT |
ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT;
@@ -848,7 +857,9 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
(ARM_LPAE_MAIR_ATTR_WBRWA
<< ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_CACHE)) |
(ARM_LPAE_MAIR_ATTR_DEVICE
- << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_DEV));
+ << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_DEV)) |
+ (ARM_LPAE_MAIR_ATTR_QCOM_SYS_CACHE
+ << ARM_LPAE_MAIR_ATTR_SHIFT(ARM_LPAE_MAIR_ATTR_IDX_QCOM_SYS_CACHE));

cfg->arm_lpae_s1_cfg.mair[0] = reg;
cfg->arm_lpae_s1_cfg.mair[1] = 0;
diff --git a/drivers/iommu/io-pgtable.h b/drivers/iommu/io-pgtable.h
index 46604cf7b017..fb237e8aa9f1 100644
--- a/drivers/iommu/io-pgtable.h
+++ b/drivers/iommu/io-pgtable.h
@@ -80,6 +80,9 @@ struct io_pgtable_cfg {
* pagetables even on a coherent SMMU for cases where reducing
* snoop traffic/latency on walks outweighs the cost of cache
* maintenance on PTE updates.
+ *
+ * IO_PGTABLE_QUIRK_QCOM_SYS_CACHE: Force using outer system cache
+ * for non-coherent devices on Qcom platforms.
*/
#define IO_PGTABLE_QUIRK_ARM_NS BIT(0)
#define IO_PGTABLE_QUIRK_NO_PERMS BIT(1)
@@ -88,6 +91,7 @@ struct io_pgtable_cfg {
#define IO_PGTABLE_QUIRK_NO_DMA BIT(4)
#define IO_PGTABLE_QUIRK_NON_STRICT BIT(5)
#define IO_PGTABLE_QUIRK_NON_COHERENT BIT(6)
+ #define IO_PGTABLE_QUIRK_QCOM_SYS_CACHE BIT(7)
unsigned long quirks;
unsigned long pgsize_bitmap;
unsigned int ias;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e90da6b6f3d1..08bb6befad5e 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -31,6 +31,7 @@
#define IOMMU_CACHE (1 << 2) /* DMA cache coherency */
#define IOMMU_NOEXEC (1 << 3)
#define IOMMU_MMIO (1 << 4) /* e.g. things like MSI doorbells */
+#define IOMMU_QCOM_SYS_CACHE (1 << 6)
/*
* Where the bus hardware includes a privilege level as part of its access type
* markings, and certain devices are capable of issuing transactions marked as
@@ -125,6 +126,7 @@ enum iommu_attr {
DOMAIN_ATTR_FSL_PAMUV1,
DOMAIN_ATTR_NESTING, /* two stages of translation */
DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE,
+ DOMAIN_ATTR_QCOM_SYS_CACHE,
DOMAIN_ATTR_MAX,
};

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
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