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

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@codeaurora.org

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

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?

•   pm_runtime_put_sync_suspend(gi2c->se.dev);
  

+}

static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev) { int ret;