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authorJonathan Cameron <Jonathan.Cameron@huawei.com>2022-02-01 15:34:37 +0000
committerDan Williams <dan.j.williams@intel.com>2022-02-08 23:15:33 -0800
commit74b0fe80409733055971bbfaf33c80a33fddeeb3 (patch)
treedbd65485b3739f26d2ced8a12d167d90b8db9c1c
parent7004cc9d1585fb7fc9ec7e3e92b70b65e13b11fd (diff)
downloadlinux-74b0fe80409733055971bbfaf33c80a33fddeeb3.tar.bz2
cxl/regs: Fix size of CXL Capability Header Register
In CXL 2.0, 8.2.5.1 CXL Capability Header Register: this register is given as 32 bits. 8.2.3 which covers the CXL 2.0 Component registers, including the CXL Capability Header Register states that access restrictions specified in Section 8.2.2 apply. 8.2.2 includes: * A 32 bit register shall be accessed as a 4 Byte quantity. ... If these rules are not followed, the behavior is undefined. Discovered during review of CXL QEMU emulation. Alex Bennée pointed out there was a comment saying that 4 byte registers must be read with a 4 byte read, but 8 byte reads were being emulated. https://lore.kernel.org/qemu-devel/87bkzyd3c7.fsf@linaro.org/ Fixing that, led to this code failing. Whilst a given hardware implementation 'might' work with an 8 byte read, it should not be relied upon. The QEMU emulation v5 will return 0 and log the wrong access width. The code moved, so one fixes tag for where this will directly apply and also a reference to the earlier introduction of the code for backports. Fixes: 0f06157e0135 ("cxl/core: Move register mapping infrastructure") Fixes: 08422378c4ad ("cxl/pci: Add HDM decoder capabilities") Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Ben Widawsky <ben.widawsky@intel.com> Link: https://lore.kernel.org/r/20220201153437.2873-1-Jonathan.Cameron@huawei.com Signed-off-by: Dan Williams <dan.j.williams@intel.com>
-rw-r--r--drivers/cxl/core/regs.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
index 718b6b0ae4b3..39a129c57d40 100644
--- a/drivers/cxl/core/regs.c
+++ b/drivers/cxl/core/regs.c
@@ -36,7 +36,7 @@ void cxl_probe_component_regs(struct device *dev, void __iomem *base,
struct cxl_component_reg_map *map)
{
int cap, cap_count;
- u64 cap_array;
+ u32 cap_array;
*map = (struct cxl_component_reg_map) { 0 };
@@ -46,7 +46,7 @@ void cxl_probe_component_regs(struct device *dev, void __iomem *base,
*/
base += CXL_CM_OFFSET;
- cap_array = readq(base + CXL_CM_CAP_HDR_OFFSET);
+ cap_array = readl(base + CXL_CM_CAP_HDR_OFFSET);
if (FIELD_GET(CXL_CM_CAP_HDR_ID_MASK, cap_array) != CM_CAP_HDR_CAP_ID) {
dev_err(dev,