On 15/08/2019 07:06, Felipe Balbi wrote:


Vicente Bergas <vice...@gmail.com> writes:

On Wednesday, August 14, 2019 3:12:26 PM CEST, Robin Murphy wrote:
On 14/08/2019 13:53, Vicente Bergas wrote:
On Monday, July 22, 2019 4:31:27 PM CEST, Vicente Bergas wrote: ...

This particular change looks like it's implicitly specific to
RK3399, which wouldn't be ideal. Presumably if the core dwc3
driver implemented shutdown correctly (echoing parts of
dwc3_remove(), I guess) then the glue layers shouldn't need
anything special anyway.


I just checked simple->resets from dwc3-of-simple.c and it is an array
with multiple resets whereas dwc->reset from core.c is NULL.
So the reset seems specific to the glue layers.
Is there another way than resetting the thing that is
generic enough to go to core.c and allows kexec?

This is a really odd 'failure'. We do full soft reset during driver
initialization on dwc3. We shouldn't need to assert reset on shutdown,

Probing/initialisation has never been the problem. The issue for the kexec case is that when the first kernel shuts down, there is currently nothing to quiesce the controller (since only driver->shutdown gets called, not driver->remove), and thus (presumably) external USB activity causes it to keep writing back over the memory where the descriptors/command ring used to be while the second kernel boots. The second kernel will eventually probe and reset it appropriately, but by that time the damage is already done.

Yanking on a hardware reset line when the first kernel shuts down is certainly one way to stop any memory accesses if such a control is available, but presumably there's a general software way to gracefully disable the controller's DMA functions until a subsequent probe can fully reset it again - I think that would be the preferable solution.


I think the problem is here:

        if (simple->pulse_resets) {
                ret = reset_control_reset(simple->resets);
                if (ret)
                        goto err_resetc_put;
        } else {
                ret = reset_control_deassert(simple->resets);
                if (ret)
                        goto err_resetc_put;

Note that if pulse_resets is set, we will run a reset. But if
pulse_resets is false and need_reset is true, we deassert the reset.

I think below patch is enough:

diff --git a/drivers/usb/dwc3/dwc3-of-simple.c 
index bdac3e7d7b18..9a2f3e09aa2e 100644
--- a/drivers/usb/dwc3/dwc3-of-simple.c
+++ b/drivers/usb/dwc3/dwc3-of-simple.c
@@ -72,7 +72,15 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
                ret = reset_control_reset(simple->resets);
                if (ret)
                        goto err_resetc_put;
-       } else {
+       }
+       if (simple->need_reset) {
+               ret = reset_control_assert(simple->resets);
+               if (ret)
+                       goto err_resetc_put;
+               usleep_range(1000, 2000);
                ret = reset_control_deassert(simple->resets);
                if (ret)
                        goto err_resetc_put;
@@ -121,9 +129,6 @@ static int dwc3_of_simple_remove(struct platform_device 
        clk_bulk_put_all(simple->num_clocks, simple->clks);
        simple->num_clocks = 0;
- if (!simple->pulse_resets)
-               reset_control_assert(simple->resets);

Can you test?

Reply via email to