Re: [PATCH] iommu: silence iommu group prints

Laurentiu Tudor Wed, 04 Mar 2020 02:48:24 -0800



On 04.03.2020 12:07, Russell King - ARM Linux admin wrote:

On Wed, Mar 04, 2020 at 11:56:53AM +0200, Laurentiu Tudor wrote:

 From 44ae46501b5379bd0890df87fd3827248626ed03 Mon Sep 17 00:00:00 2001
From: Laurentiu Tudor <[email protected]>
Date: Tue, 1 Oct 2019 16:22:48 +0300
Subject: [PATCH 1/6] bus: fsl-mc: make mc work with smmu disable bypass on
Content-Type: text/plain; charset="us-ascii"

Since this commit [1] booting kernel on MC based chips started to
fail because this firmware starts before the kernel and as soon as
SMMU is probed it starts to trigger contiguous faults.


I think you mean "continuous" here.


Yes, thanks.

This is a workaround that allows MC firmware to run with SMMU
in disable bypass mode. It consists of the following steps:
  1. pause the firmware at early boot to get a chance to setup SMMU
  2. request direct mapping for MC device
  3. resume the firmware
The workaround relies on the fact that no state is lost when
pausing / resuming firmware, as per the docs.
With this patch, platforms with MC firmware can now boot without
having to change the default config to set:
   CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT=n


This alone is a definite improvement, and has been needed for a while.
Please submit this patch with an appropriate Fixes: tag so stable trees
can pick it up.

The thing is that probably this workaround will never make it in thekernel because it questionable to say the least, e.g. see [1]. My planis to give this approach [2] a try sometime soon.


[1] https://patchwork.kernel.org/comment/23149049/
[2] https://patchwork.kernel.org/cover/11279577/

---
Best Regards, Laurentiu

[1] 954a03be033 ("iommu/arm-smmu: Break insecure users by disabling bypass by 
default")


Please put this where you're referencing it above - it's fine to wrap
the description of the commit when using it in the body of the commit
message.  However, that should _never_ when providing a Fixes: tag
(linux-next has a script which will detect and complain about broken
Fixes: tags.)

Thanks.


Signed-off-by: Laurentiu Tudor <[email protected]>
---
  drivers/bus/fsl-mc/fsl-mc-bus.c | 53 +++++++++++++++++++++++++++++++++
  1 file changed, 53 insertions(+)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index a0f8854acb3a..683a6401ffe8 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -18,6 +18,8 @@
  #include <linux/bitops.h>
  #include <linux/msi.h>
  #include <linux/dma-mapping.h>
+#include <linux/iommu.h>
+#include <linux/io.h>

#include "fsl-mc-private.h"@@ -889,6 +891,12 @@ static int get_mc_addr_translation_ranges(struct device *dev,

        return 0;
  }

+#define FSL_MC_GCR1 0x0

+#define GCR1_P1_STOP   BIT(31)
+
+static u32 boot_gcr1;
+static void __iomem *fsl_mc_regs;
+
  /**
   * fsl_mc_bus_probe - callback invoked when the root MC bus is being
   * added
@@ -906,6 +914,21 @@ static int fsl_mc_bus_probe(struct platform_device *pdev)
        struct mc_version mc_version;
        struct resource res;

+ /*

+        * The MC firmware requires full access to the whole address space plus
+        * it has no way of dealing with any kind of address translation, so
+        * request direct mapping for it.
+        */
+       error = iommu_request_dm_for_dev(&pdev->dev);
+       if (error)
+               dev_warn(&pdev->dev, "iommu_request_dm_for_dev() failed: %d\n",
+                        error);
+
+       if (fsl_mc_regs) {
+               /* Resume the firmware */
+               writel(boot_gcr1 & ~GCR1_P1_STOP, fsl_mc_regs + FSL_MC_GCR1);
+       }
+
        mc = devm_kzalloc(&pdev->dev, sizeof(*mc), GFP_KERNEL);
        if (!mc)
                return -ENOMEM;
@@ -990,6 +1013,13 @@ static int fsl_mc_bus_remove(struct platform_device *pdev)
        if (!fsl_mc_is_root_dprc(&mc->root_mc_bus_dev->dev))
                return -EINVAL;

+ /*

+        * Pause back the firmware so that it doesn't trigger faults by the
+        * time SMMU gets brought down.
+        */
+       writel(boot_gcr1 | GCR1_P1_STOP, fsl_mc_regs + FSL_MC_GCR1);
+       iounmap(fsl_mc_regs);
+
        fsl_mc_device_remove(mc->root_mc_bus_dev);

fsl_destroy_mc_io(mc->root_mc_bus_dev->mc_io);

@@ -1018,6 +1048,8 @@ static struct platform_driver fsl_mc_bus_driver = {
  static int __init fsl_mc_bus_driver_init(void)
  {
        int error;
+       struct device_node *np;
+       struct resource res;

error = bus_register(&fsl_mc_bus_type);

        if (error < 0) {
@@ -1039,9 +1071,30 @@ static int __init fsl_mc_bus_driver_init(void)
        if (error < 0)
                goto error_cleanup_dprc_driver;

+ np = of_find_matching_node(NULL, fsl_mc_bus_match_table);

+       if (np && of_device_is_available(np)) {
+               error = of_address_to_resource(np, 1, &res);
+               if (error)
+                       goto error_cleanup_dprc_driver;
+               fsl_mc_regs = ioremap(res.start, resource_size(&res));
+               if (!fsl_mc_regs) {
+                       error = -ENXIO;
+                       goto error_cleanup_dprc_driver;
+               }
+
+               boot_gcr1 = readl(fsl_mc_regs + FSL_MC_GCR1);
+               /*
+                * If found running, pause MC firmware in order to get a chance
+                * to setup SMMU for it.
+                */
+               if (!(boot_gcr1 & GCR1_P1_STOP))
+                       writel(boot_gcr1 | GCR1_P1_STOP,  fsl_mc_regs + 
FSL_MC_GCR1);
+       }
+
        return 0;

error_cleanup_dprc_driver:

+       iounmap(fsl_mc_regs);
        dprc_driver_exit();

error_cleanup_driver:

--
2.17.1

_______________________________________________
iommu mailing list
[email protected]
https://lists.linuxfoundation.org/mailman/listinfo/iommu

Re: [PATCH] iommu: silence iommu group prints

Reply via email to