[PATCH net v1] idpf: read lower clock bits inside the time sandwich

[Mina Almasry <almasrymina@google.com>]

PCIe reads need to be done inside the time sandwich because PCIe
writes may get buffered in the PCIe fabric and posted to the device
after the _postts completes. Doing the PCIe read inside the time
sandwich guarantees that the write gets flushed before the _postts
timestamp is taken.

Cc: lrizzo@google.com
Cc: namangulati@google.com
Cc: willemb@google.com
Cc: intel-wired-lan@lists.osuosl.org
Cc: milena.olech@intel.com
Cc: jacob.e.keller@intel.com

Fixes: 5cb8805d2366 ("idpf: negotiate PTP capabilities and get PTP clock")
Suggested-by: Shachar Raindel <shacharr@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
---
 drivers/net/ethernet/intel/idpf/idpf_ptp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_ptp.c b/drivers/net/ethernet/intel/idpf/idpf_ptp.c
index 3e1052d070cf..0a8b50350b86 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_ptp.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_ptp.c
@@ -108,11 +108,11 @@ static u64 idpf_ptp_read_src_clk_reg_direct(struct idpf_adapter *adapter,
 	ptp_read_system_prets(sts);
 
 	idpf_ptp_enable_shtime(adapter);
+	lo = readl(ptp->dev_clk_regs.dev_clk_ns_l);
 
 	/* Read the system timestamp post PHC read */
 	ptp_read_system_postts(sts);
 
-	lo = readl(ptp->dev_clk_regs.dev_clk_ns_l);
 	hi = readl(ptp->dev_clk_regs.dev_clk_ns_h);
 
 	spin_unlock(&ptp->read_dev_clk_lock);

base-commit: 885bebac9909994050bbbeed0829c727e42bd1b7
-- 
2.52.0.223.gf5cc29aaa4-goog