Re: [PATCH v1 3/3] PCI: brcmstb: Allow setting the completion timeout

From: Stefan Wahren
Date: Thu Apr 06 2023 - 11:59:54 EST


Hi Jim,

Am 06.04.23 um 14:46 schrieb Jim Quinlan:
Since the STB PCIe HW will cause a CPU abort on a completion timeout abort,
we might as well extend the timeout limit. Further, different devices and
systems may requires a larger or smaller amount for L1SS exit.

Signed-off-by: Jim Quinlan <jim2101024@xxxxxxxxx>
---
drivers/pci/controller/pcie-brcmstb.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 129eee7bdbc1..92d78f4dfaae 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -1080,6 +1080,29 @@ static void brcm_config_clkreq(struct brcm_pcie *pcie)
writel(clkreq_set, pcie->base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
}
+static void brcm_config_completion_timeout(struct brcm_pcie *pcie)
+{
+ /* TIMEOUT register is two registers before RGR1_SW_INIT_1 */
+ const unsigned int REG_OFFSET = PCIE_RGR1_SW_INIT_1(pcie) - 8;
+ u32 timeout, timeout_msec = 1000;
+ u64 tmp64;
+ int ret;
+
+ ret = of_property_read_u32(pcie->np, "brcm,completion-abort-msecs",
+ &timeout_msec);
+
+ if (ret && ret != -EINVAL)
+ dev_err(pcie->dev, "bad 'brcm,completion-abort-msecs' prop\n");

i'm not sure about the error behavior. If we want to proceed with defaults in such a case, i would make this a warning and mention the used defaults.

+
+ /* Each unit in timeout register is 1/216,000,000 seconds */
+ tmp64 = (u64)216000 * timeout_msec;
+
+ /* Clamp the requested value before writing it */
+ timeout = tmp64 > 0xffffffff ? 0xffffffff : tmp64;
+ timeout = timeout < 0xffff ? 0xffff : timeout;

Personally i'm not a huge fan of silently clamping wrong DT values.

Best regards

+ writel(timeout, pcie->base + REG_OFFSET);
+}
+
static int brcm_pcie_start_link(struct brcm_pcie *pcie)
{
struct device *dev = pcie->dev;
@@ -1110,6 +1133,7 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
return -ENODEV;
}
+ brcm_config_completion_timeout(pcie);
brcm_config_clkreq(pcie);
if (pcie->gen)