Re: [PATCH v1] iommu/ipmmu-vmsa: Don't register as BUS IOMMU if machine doesn't have IPMMU-VMSA

Hi Laurent,

On Fri, Jul 27, 2018 at 11:09 AM Laurent Pinchart
[off-list ref] wrote:

(CC'ing Geert and Magnus)

Thank you for the patch.

On Friday, 27 July 2018 00:19:16 EEST Dmitry Osipenko wrote:

quoted

This fixes kernel crashing on NVIDIA Tegra if kernel is compiled in
a multiplatform configuration and IPMMU-VMSA driver is enabled.

Cc: <redacted> # v3.20+
Signed-off-by: Dmitry Osipenko <redacted>
---
 drivers/iommu/ipmmu-vmsa.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index 9e8495762bc8..78c50db9cd71 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c

@@ -1109,12 +1109,19 @@ static struct platform_driver ipmmu_driver = {

 static int __init ipmmu_init(void)
 {
+     struct device_node *np;
      static bool setup_done;
      int ret;

      if (setup_done)
              return 0;

+     np = of_find_matching_node(NULL, ipmmu_of_ids);
+     if (!np)
+             return 0;
+
+     of_node_put(np);
+

While functionally correct, this will add some unnecessary overhead when
iommu_init() is called from IOMMU_OF_DECLARE(). I'm OK with this fix as a
temporary measure to solve your problem, but we need to address the underlying
issue properly.

Geert, Magnus, the ipmmu-vmsa driver is a bit of a mess. We should brush it up
and start using IOMMU_OF_DECLARE() on all platforms (and eventually get rid of
bus_set_iommu() completely...). Do you have plans to address this ? If not,
could you please add it to your to-do list ?

On the contrary: IOMMU_OF_DECLARE() has been removed.

quoted

      ret = platform_driver_register(&ipmmu_driver);
      if (ret < 0)
              return ret;

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds