Re: [PATCH V2 2/2] i2c: i2c-qcom-geni: Add shutdown callback for i2c

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On 2020-08-21 05:52, Stephen Boyd wrote:
Quoting Roja Rani Yarubandi (2020-08-20 03:35:22)
If the hardware is still accessing memory after SMMU translation
is disabled (as part of smmu shutdown callback), then the
IOVAs (I/O virtual address) which it was using will go on the bus
as the physical addresses which will result in unknown crashes
like NoC/interconnect errors.

So, implement shutdown callback to i2c driver to unmap DMA mappings
during system "reboot" or "shutdown".

Signed-off-by: Roja Rani Yarubandi <rojay@xxxxxxxxxxxxxx>
---

I'd still put a Fixes tag because it's fixing the driver when someone
runs shutdown.


Okay, will add fixes tag.

Changes in V2:
- As per Stephen's comments added seperate function for stop transfer,
   fixed minor nitpicks.

drivers/i2c/busses/i2c-qcom-geni.c | 43 ++++++++++++++++++++++++++++++
 include/linux/qcom-geni-se.h       |  5 ++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 1fda5c7c2cfc..d07f2f33bb75 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -486,6 +486,28 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
        return ret;
 }

+static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
+{
+       u32 val;
+       struct geni_se *se = &gi2c->se;
+
+       val = readl_relaxed(gi2c->se.base + SE_DMA_DEBUG_REG0);
+       if (val & DMA_TX_ACTIVE) {
+               geni_i2c_abort_xfer(gi2c);
+               gi2c->cur_wr = 0;
+               if (gi2c->err)
+                       geni_i2c_tx_fsm_rst(gi2c);
+ geni_se_tx_dma_unprep(se, gi2c->tx_dma, gi2c->xfer_len);
+       }
+       if (val & DMA_RX_ACTIVE) {
+               geni_i2c_abort_xfer(gi2c);
+               gi2c->cur_rd = 0;
+               if (gi2c->err)
+                       geni_i2c_rx_fsm_rst(gi2c);
+ geni_se_rx_dma_unprep(se, gi2c->rx_dma, gi2c->xfer_len);
+       }
+}
+
 static u32 geni_i2c_func(struct i2c_adapter *adap)
 {
return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK); @@ -617,6 +639,26 @@ static int geni_i2c_remove(struct platform_device *pdev)
        return 0;
 }

+static void geni_i2c_shutdown(struct platform_device *pdev)
+{
+       int ret;
+       u32 dma;
+       struct geni_i2c_dev *gi2c = platform_get_drvdata(pdev);
+       struct geni_se *se = &gi2c->se;
+
+       ret = pm_runtime_get_sync(gi2c->se.dev);
+       if (ret < 0) {
+ dev_err(gi2c->se.dev, "Failed to resume device: %d\n", ret);
+               return;
+       }
+
+       dma = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
+       if (dma)
+               geni_i2c_stop_xfer(gi2c);

Any reason the if (dma) check isn't inside geni_i2c_stop_xfer()?
Checking for dma and then bailing out early should work and keep the
logic in one function. Then the pm_runtime_sync() call could go in there
too and if (!dma) goto out. This assumes that we're going to call
geni_i2c_stop_xfer() from somewhere else, like if a transfer times out
or something?


Okay, will do the changes.

+
+       pm_runtime_put_sync_suspend(gi2c->se.dev);
+}
+
static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
 {
        int ret;



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