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Message-ID: <71e7b6f8-67f2-4c03-b83a-71d7e747ad04@linaro.org>
Date: Wed, 22 May 2024 15:18:18 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Nícolas F. R. A. Prado <nfraprado@...labora.com>,
Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] spi: Remove unneded check for orig_nents
Hi,
On 22/05/2024 13:53, Neil Armstrong wrote:
> On 22/05/2024 13:33, Andy Shevchenko wrote:
>> On Wed, May 22, 2024 at 12:03:33PM +0200, Neil Armstrong wrote:
>>> On 15/05/2024 23:09, Nícolas F. R. A. Prado wrote:
>>>> On Tue, May 07, 2024 at 11:10:27PM +0300, Andy Shevchenko wrote:
>>>>> Both dma_unmap_sgtable() and sg_free_table() in spi_unmap_buf_attrs()
>>>>> have checks for orig_nents against 0. No need to duplicate this.
>>>>> All the same applies to other DMA mapping API calls.
>>>>>
>>>>> Also note, there is no other user in the kernel that does this kind of
>>>>> checks.
>>>>>
>>>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>>>>
>>>> Hi,
>>>>
>>>> this commit caused a regression which I reported here:
>>>>
>>>> https://lore.kernel.org/all/d3679496-2e4e-4a7c-97ed-f193bd53af1d@notapiano
>>>>
>>>> along with some thoughts on the cause and a possible solution, though I'm not
>>>> familiar with this code base at all and would really appreciate any feedback you
>>>> may have.
>>>
>>> I also see the same regression on the SM8550 and SM8650 platforms,
>>> please CC linux-arm-msm@...r.kernel.org and me for a potential fix to test on those platforms.
>>
>> There is still no answer from IOMMU patch author. Do you have the same trace
>> due to IOMMU calls? Anyway, I guess it would be nice to see it.
>
> Yes :
> [ 6.404623] Unable to handle kernel NULL pointer dereference at virtual address 000000000000001c
> <snip>
> [ 6.641597] lr : __dma_sync_sg_for_device+0x3c/0x40
> <snip>
> [ 6.688286] Call trace:
> [ 6.688287] iommu_dma_sync_sg_for_device+0x28/0x100
> [ 6.717582] __dma_sync_sg_for_device+0x3c/0x40
> [ 6.717585] spi_transfer_one_message+0x358/0x680
> [ 6.732229] __spi_pump_transfer_message+0x188/0x494
> [ 6.732232] __spi_sync+0x2a8/0x3c4
> [ 6.732234] spi_sync+0x30/0x54
> [ 6.732236] goodix_berlin_spi_write+0xf8/0x164 [goodix_berlin_spi]
> [ 6.739854] _regmap_raw_write_impl+0x538/0x674
> [ 6.750053] _regmap_raw_write+0xb4/0x144
> [ 6.750056] regmap_raw_write+0x7c/0xc0
> [ 6.750058] goodix_berlin_power_on+0xb0/0x1b0 [goodix_berlin_core]
> [ 6.765520] goodix_berlin_probe+0xc0/0x660 [goodix_berlin_core]
> [ 6.765522] goodix_berlin_spi_probe+0x12c/0x14c [goodix_berlin_spi]
> [ 6.772339] spi_probe+0x84/0xe4
> [ 6.772342] really_probe+0xbc/0x29c
> [ 6.784313] __driver_probe_device+0x78/0x12c
> [ 6.784316] driver_probe_device+0x3c/0x15c
> [ 6.784319] __driver_attach+0x90/0x19c
> [ 6.784322] bus_for_each_dev+0x7c/0xdc
> [ 6.794520] driver_attach+0x24/0x30
> [ 6.794523] bus_add_driver+0xe4/0x208
> [ 6.794526] driver_register+0x5c/0x124
> [ 6.802586] __spi_register_driver+0xa4/0xe4
> [ 6.802589] goodix_berlin_spi_driver_init+0x20/0x1000 [goodix_berlin_spi]
> [ 6.802591] do_one_initcall+0x80/0x1c8
> [ 6.902310] do_init_module+0x60/0x218
> [ 6.921988] load_module+0x1bcc/0x1d8c
> [ 6.925847] init_module_from_file+0x88/0xcc
> [ 6.930238] __arm64_sys_finit_module+0x1dc/0x2e4
> [ 6.935074] invoke_syscall+0x48/0x114
> [ 6.938944] el0_svc_common.constprop.0+0xc0/0xe0
> [ 6.943781] do_el0_svc+0x1c/0x28
> [ 6.947195] el0_svc+0x34/0xd8
> [ 6.950348] el0t_64_sync_handler+0x120/0x12c
> [ 6.954833] el0t_64_sync+0x190/0x194
> [ 6.958600] Code: 2a0203f5 2a0303f6 a90363f7 aa0003f7 (b9401c2
>
> Reverting 8cc3bad9d9d6 ("spi: Remove unneded check for orig_nents") removes the crash.
>
>>
>> Meanwhile, I have three changes I posted in the replies to the initial report,
>> can you combine them all and test? This will be a plan B (? or A, depending on
>> the culprit).
>>
>
> I'll try to apply them and test.
I stacked the 3 changes, and it works:
Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD
For reference, the changeset looks like:
============><============================================================================================
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 289feccca376..0851c5e1fd1f 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1220,6 +1220,11 @@ void spi_unmap_buf(struct spi_controller *ctlr, struct device *dev,
spi_unmap_buf_attrs(ctlr, dev, sgt, dir, 0);
}
+/* Dummy SG for unidirect transfers */
+static struct scatterlist dummy_sg = {
+ .page_link = SG_END,
+};
+
static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
{
struct device *tx_dev, *rx_dev;
@@ -1243,6 +1248,7 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
else
rx_dev = ctlr->dev.parent;
+ ret = -ENOMSG;
list_for_each_entry(xfer, &msg->transfers, transfer_list) {
/* The sync is done before each transfer. */
unsigned long attrs = DMA_ATTR_SKIP_CPU_SYNC;
@@ -1257,6 +1263,9 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
attrs);
if (ret != 0)
return ret;
+ } else {
+ memset(&xfer->tx_sg, 0, sizeof(xfer->tx_sg));
+ xfer->tx_sg.sgl = &dummy_sg;
}
if (xfer->rx_buf != NULL) {
@@ -1270,8 +1279,14 @@ static int __spi_map_msg(struct spi_controller *ctlr, struct spi_message *msg)
return ret;
}
+ } else {
+ memset(&xfer->rx_sg, 0, sizeof(xfer->rx_sg));
+ xfer->rx_sg.sgl = &dummy_sg;
}
}
+ /* No transfer has been mapped, bail out with success */
+ if (ret)
+ return 0;
ctlr->cur_rx_dma_dev = rx_dev;
ctlr->cur_tx_dma_dev = tx_dev;
============><============================================================================================
Thanks,
Neil
>
> Neil
>
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