Re: [PATCH V11 03/12] PCI: dwc: Perform dbi regs write lock towards the end
From: Vidya Sagar
Date: Thu Jun 27 2019 - 12:52:17 EST
On 6/27/2019 9:20 PM, Lorenzo Pieralisi wrote:
On Thu, Jun 27, 2019 at 09:03:08PM +0530, Vidya Sagar wrote:
On 6/27/2019 8:28 PM, Lorenzo Pieralisi wrote:
On Mon, Jun 24, 2019 at 02:44:56PM +0530, Vidya Sagar wrote:
Remove multiple write enable and disable sequences of dbi registers as
Tegra194 implements writes to BAR-0 register (offset: 0x10) controlled by
DBI write-lock enable bit thereby not allowing any further writes to BAR-0
register in config space to take place. Hence enabling write permission at
the start of function and disabling the same only towards the end.
I do not understand what this patch does, I would like to rephrase
the commit log in a way that is easier to parse.
In particular I do not get what you mean in relation to BAR-0, I am
confused, please clarify.
Lorenzo
Well, some of the Synopsys DesignWare core's DBI registers are
protected with a lock without which, they are read-only by default.
Existing code in dw_pcie_setup_rc() API tries to unlock and lock
multiple times whenever it wants to update those write-protected
registers. This patch attempts to unlock all such write-protected
registers for writing once in the beginning of the function and lock
them back towards the end. As far as BAR-0 register (which is at
offset 0x10 in DBI space... nothing but the config space) in Tegra194
is concerned, it is one of those registers to which writes are
protected. I could have added unlock/lock pair around accessing this
register, but that would bloat this API with one more pair of
unlock/lock, instead I chose to remove unlock/lock pairs for all
protected registers and have unlock in the beginning and lock towards
the end.
Ok, so DBI space registers that require write permissions are per-IP.
This is clearer so the commit log must be rewritten, it is not clear at
all in this respect at least not as-is, if you read it you will
notice ;-)
Ok. I'll update commit message in next patch series.
-Vidya Sagar
Lorenzo
-Vidya Sagar
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
Reviewed-by: Thierry Reding <treding@xxxxxxxxxx>
Acked-by: Jingoo Han <jingoohan1@xxxxxxxxx>
---
Changes since [v10]:
* None
Changes since [v9]:
* None
Changes since [v8]:
* None
Changes since [v7]:
* None
Changes since [v6]:
* None
Changes since [v5]:
* Moved write enable to the beginning of the API and write disable to the end
Changes since [v4]:
* None
Changes since [v3]:
* None
Changes since [v2]:
* None
Changes since [v1]:
* None
drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index f93252d0da5b..d3156446ff27 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -628,6 +628,12 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
u32 val, ctrl, num_ctrls;
struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+ /*
+ * Enable DBI read-only registers for writing/updating configuration.
+ * Write permission gets disabled towards the end of this function.
+ */
+ dw_pcie_dbi_ro_wr_en(pci);
+
dw_pcie_setup(pci);
if (!pp->ops->msi_host_init) {
@@ -650,12 +656,10 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
dw_pcie_writel_dbi(pci, PCI_BASE_ADDRESS_1, 0x00000000);
/* Setup interrupt pins */
- dw_pcie_dbi_ro_wr_en(pci);
val = dw_pcie_readl_dbi(pci, PCI_INTERRUPT_LINE);
val &= 0xffff00ff;
val |= 0x00000100;
dw_pcie_writel_dbi(pci, PCI_INTERRUPT_LINE, val);
- dw_pcie_dbi_ro_wr_dis(pci);
/* Setup bus numbers */
val = dw_pcie_readl_dbi(pci, PCI_PRIMARY_BUS);
@@ -687,15 +691,13 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
dw_pcie_wr_own_conf(pp, PCI_BASE_ADDRESS_0, 4, 0);
- /* Enable write permission for the DBI read-only register */
- dw_pcie_dbi_ro_wr_en(pci);
/* Program correct class for RC */
dw_pcie_wr_own_conf(pp, PCI_CLASS_DEVICE, 2, PCI_CLASS_BRIDGE_PCI);
- /* Better disable write permission right after the update */
- dw_pcie_dbi_ro_wr_dis(pci);
dw_pcie_rd_own_conf(pp, PCIE_LINK_WIDTH_SPEED_CONTROL, 4, &val);
val |= PORT_LOGIC_SPEED_CHANGE;
dw_pcie_wr_own_conf(pp, PCIE_LINK_WIDTH_SPEED_CONTROL, 4, val);
+
+ dw_pcie_dbi_ro_wr_dis(pci);
}
EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
--
2.17.1