[PATCH] PCI: imx6: fix boot hang when link already enabled

[PATCH] PCI: imx6: fix boot hang when link already enabled

[Fabio Estevam]

From: Fabio Estevam <fabio.estevam@freescale.com>

This fixes a boot hang observed when the bootloader
already enabled the PCIe link for it's own use. The
fundamental problem is that Freescale forgot to wire
up the core reset, so software doesn't have a sane way
to get the core into a defined state.

According to the DW PCIe core reference manual configuration
of the core may only happen when the LTSSM is disabled, so
this is one of the first things we do. Apparently this isn't
safe to do when the LTSSM is in any other state than
"detect" as we observe an instant machine hang when trying to
do so while the link is already up.

As a workaround force LTSSM into detect state right before
hitting the disable switch.

Tested on a mx6qsabresd board with PCI driver enabled in the 
bootloader and also with PCI driver disabled in the bootloader.
The kernel boots succesfully on both cases now.

Cc: <stable@vger.kernel.org> # 3.16
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
---
 drivers/pci/host/pci-imx6.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index a568efa..2fa6d3a 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -49,6 +49,9 @@ struct imx6_pcie {
 
 /* PCIe Port Logic registers (memory-mapped) */
 #define PL_OFFSET 0x700
+#define PCIE_PL_PFLR				(PL_OFFSET + 0x08)
+#define PCIE_PL_PFLR_LINK_STATE_MASK		(0x3f << 16)
+#define PCIE_PL_PFLR_FORCE_LINK			(1 << 15)
 #define PCIE_PHY_DEBUG_R0 (PL_OFFSET + 0x28)
 #define PCIE_PHY_DEBUG_R1 (PL_OFFSET + 0x2c)
 #define PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING	(1 << 29)
@@ -214,7 +217,19 @@ static int imx6q_pcie_abort_handler(unsigned long addr,
 static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
 {
 	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
+	u32 val;
+
+	regmap_read(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12, &val);
 
+	if (val & IMX6Q_GPR12_PCIE_CTL_2) {
+		val = readl(pp->dbi_base + PCIE_PL_PFLR);
+		val &= ~PCIE_PL_PFLR_LINK_STATE_MASK;
+		val |= PCIE_PL_PFLR_FORCE_LINK;
+		writel(val, pp->dbi_base + PCIE_PL_PFLR);
+
+		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
+				   IMX6Q_GPR12_PCIE_CTL_2, 0 << 10);
+	}
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
 			IMX6Q_GPR1_PCIE_TEST_PD, 1 << 18);
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
-- 
1.9.1

Re: [PATCH] PCI: imx6: fix boot hang when link already enabled

[Shawn Guo]

On Wed, Aug 06, 2014 at 05:14:39PM -0300, Fabio Estevam wrote:
> From: Fabio Estevam <fabio.estevam@freescale.com>
> 
> This fixes a boot hang observed when the bootloader
> already enabled the PCIe link for it's own use. The
> fundamental problem is that Freescale forgot to wire
> up the core reset, so software doesn't have a sane way
> to get the core into a defined state.
> 
> According to the DW PCIe core reference manual configuration
> of the core may only happen when the LTSSM is disabled, so
> this is one of the first things we do. Apparently this isn't
> safe to do when the LTSSM is in any other state than
> "detect" as we observe an instant machine hang when trying to
> do so while the link is already up.
> 
> As a workaround force LTSSM into detect state right before
> hitting the disable switch.
> 
> Tested on a mx6qsabresd board with PCI driver enabled in the 
> bootloader and also with PCI driver disabled in the bootloader.
> The kernel boots succesfully on both cases now.
> 
> Cc: <stable@vger.kernel.org> # 3.16
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

I believe Lucas already had a new version of his patch.

http://thread.gmane.org/gmane.linux.kernel.pci/33712/focus=33711

Shawn

> ---
>  drivers/pci/host/pci-imx6.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index a568efa..2fa6d3a 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -49,6 +49,9 @@ struct imx6_pcie {
>  
>  /* PCIe Port Logic registers (memory-mapped) */
>  #define PL_OFFSET 0x700
> +#define PCIE_PL_PFLR				(PL_OFFSET + 0x08)
> +#define PCIE_PL_PFLR_LINK_STATE_MASK		(0x3f << 16)
> +#define PCIE_PL_PFLR_FORCE_LINK			(1 << 15)
>  #define PCIE_PHY_DEBUG_R0 (PL_OFFSET + 0x28)
>  #define PCIE_PHY_DEBUG_R1 (PL_OFFSET + 0x2c)
>  #define PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING	(1 << 29)
> @@ -214,7 +217,19 @@ static int imx6q_pcie_abort_handler(unsigned long addr,
>  static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
>  {
>  	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
> +	u32 val;
> +
> +	regmap_read(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12, &val);
>  
> +	if (val & IMX6Q_GPR12_PCIE_CTL_2) {
> +		val = readl(pp->dbi_base + PCIE_PL_PFLR);
> +		val &= ~PCIE_PL_PFLR_LINK_STATE_MASK;
> +		val |= PCIE_PL_PFLR_FORCE_LINK;
> +		writel(val, pp->dbi_base + PCIE_PL_PFLR);
> +
> +		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> +				   IMX6Q_GPR12_PCIE_CTL_2, 0 << 10);
> +	}
>  	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
>  			IMX6Q_GPR1_PCIE_TEST_PD, 1 << 18);
>  	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -- 
> 1.9.1
> 

Re: [PATCH] PCI: imx6: fix boot hang when link already enabled

[Fabio Estevam]

On Wed, Aug 6, 2014 at 11:12 PM, Shawn Guo <shawn.guo@freescale.com> wrote:

> I believe Lucas already had a new version of his patch.
>
> http://thread.gmane.org/gmane.linux.kernel.pci/33712/focus=33711

Ok, I wasn't aware of the updated version.

[PATCH] PCI: imx6: fix boot hang when link already enabled

[Lucas Stach]

This fixes a boot hang observed when the bootloader
already enabled the PCIe link for it's own use. The
fundamental problem is that Freescale forgot to wire
up the core reset, so software doesn't have a sane way
to get the core into a defined state.

According to the DW PCIe core reference manual configuration
of the core may only happen when the LTSSM is disabled, so
this is one of the first things we do. Apparently this isn't
safe to do when the LTSSM is in any other state than
"detect" as we observe an instant machine hang when trying to
do so while the link is already up.

As a workaround force LTSSM into detect state right before
hitting the disable switch.

Reported-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
Fabios delay workaround worked because of the following
conditions:
1. The driver gets probed and pulls the peripheral reset GPIO
2. Peripheral is held in reset, so won't answer any link
negotiation requests
3. The LTSSM times out and falls back into detect state
after 24ms (that's why a 30ms delay helps)
4. After LTSSM entered detect state it's safe to hit the
disable switch
---
 drivers/pci/host/pci-imx6.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index afa450c54aba..1c4b4b81fe15 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -49,6 +49,9 @@ struct imx6_pcie {
 
 /* PCIe Port Logic registers (memory-mapped) */
 #define PL_OFFSET 0x700
+#define PCIE_PL_PFLR (PL_OFFSET + 0x08)
+#define PCIE_PL_PFLR_LINK_STATE_MASK		(0x3f << 16)
+#define PCIE_PL_PFLR_FORCE_LINK			(1 << 15)
 #define PCIE_PHY_DEBUG_R0 (PL_OFFSET + 0x28)
 #define PCIE_PHY_DEBUG_R1 (PL_OFFSET + 0x2c)
 #define PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING	(1 << 29)
@@ -214,6 +217,12 @@ static int imx6q_pcie_abort_handler(unsigned long addr,
 static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
 {
 	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
+	u32 val;
+
+	val = readl(pp->dbi_base + PCIE_PL_PFLR);
+	val &= ~PCIE_PL_PFLR_LINK_STATE_MASK;
+	val |= PCIE_PL_PFLR_FORCE_LINK;
+	writel(val, pp->dbi_base + PCIE_PL_PFLR);
 
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
 			IMX6Q_GPR12_PCIE_CTL_2, 0 << 10);
-- 
2.0.1