[U-Boot] [PATCH 23/23] ARM: tegra: Enable PCIe on Jetson TK1

Thierry Reding
2014-08-27T14:34:32Z

On Wed, Aug 27, 2014 at 03:28:06PM +0200, Thierry Reding wrote:
> On Tue, Aug 26, 2014 at 03:54:50PM +0300, Tuomas Tynkkynen wrote:
> > On 18/08/14 10:16, Thierry Reding wrote:
> > [...]
> > > +static int as3722_gpio_direction_output(u8 gpio, u8 level)
> > > +{
> > > + u8 value;
> > > + int err;
> > > +
> > > + if (gpio > 7)
> > > + return -EINVAL;
> > > +
> > > + if (level == 0)
> > > + value = AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDL;
> > > + else
> > > + value = AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDH;
> > > +
> > > + err = as3722_write(AS3722_GPIO_CONTROL(gpio), value);
> > > + if (err) {
> > > + error("as3722: failed to configure GPIO#%u as output: %d\n",
> > > + gpio, err);
> > > + return err;
> > > + }
> > > +
> > > + err = as3722_gpio_set(gpio, level);
> > > + if (err < 0) {
> > > + error("as3722: failed to set GPIO#%u high: %d\n", gpio, err);
> > > + return err;
> > > + }
> > > +
> > > + return 0;
> > > +}
> >
> > This function doesn't work correctly if the GPIO was originally configured
> > as inverted and low, which GPIO#2 seems to be.
> > (as3722_read(AS3722_GPIO_CONTROL(2), &value) returns value == 0x87)...
>
> That should be equivalent to what we're setting but is a somewhat weird
> default. I guess the fact that we're inverting it and then changing the
> value to high in separate transactions makes the output flip twice.
>
> > > +
> > > +int tegra_pcie_board_init(void)
> > > +{
> > [...]
> > > +
> > > + err = as3722_gpio_direction_output(2, 1);
> > > + if (err < 0) {
> > > + error("as3722: failed to set GPIO#2 high: %d\n", err);
> > > + return err;
> > > + }
> > [...]
> >
> > On my board, this call results in UART corruption, like this:
> >
> > tegra-pcie: non-prefetchable memory: 0x13000000-0x20000000
> > tegra-pcie: prefetchable memory: 0x20000000-0x40000000
> > ??????b????b2x1, 1x1 configuration
> > ??5R?tegra-pcie: probing port 1, using 1 lanes
> >
> > Likely because GPIO#2 controls the +3.3V_LP0 rail, which powers the UART
> > level shifters. Commenting the function call out fixes the corruption and
> > PCI-E still works fine.
>
> If I add a udelay(500) after the above I'm not able to reproduce the
> UART breakage anymore. But I guess making the AS3722 GPIO code smarter
> would be helpful. In the kernel this is done by checking the invert bit
> and then setting the value accordingly. I suppose the same could be done
> for the mode bits. I'll see if I can work up a patch.

How about this:
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diff --git a/drivers/power/as3722.c b/drivers/power/as3722.c
index 59d1bf1b50b0..393dc8608d07 100644
--- a/drivers/power/as3722.c
+++ b/drivers/power/as3722.c
@@ -17,6 +17,7 @@
#define AS3722_GPIO_CONTROL(n) (0x08 + (n))
#define AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDH (1 << 0)
#define AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDL (7 << 0)
+#define AS3722_GPIO_CONTROL_MODE_MASK (7 << 0)
#define AS3722_GPIO_CONTROL_INVERT (1 << 7)
#define AS3722_LDO_VOLTAGE(n) (0x10 + (n))
#define AS3722_GPIO_SIGNAL_OUT 0x20
@@ -220,10 +221,21 @@ int as3722_gpio_direction_output(struct as3722 *pmic, unsigned int gpio,
if (gpio > 7)
return -EINVAL;

+ err = as3722_read(pmic, AS3722_GPIO_CONTROL(gpio), &value);
+ if (err < 0) {
+ error("failed to read GPIO#%u control register: %d", gpio, err);
+ return err;
+ }
+
+ if (value & AS3722_GPIO_CONTROL_INVERT)
+ level = !level;
+
+ value &= ~AS3722_GPIO_CONTROL_MODE_MASK;
+
if (level == 0)
- value = AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDL;
+ value |= AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDL;
else
- value = AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDH;
+ value |= AS3722_GPIO_CONTROL_MODE_OUTPUT_VDDH;

err = as3722_write(pmic, AS3722_GPIO_CONTROL(gpio), value);
if (err) {
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