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

Hi Roja,

On 8/20/2020 4:05 PM, Roja Rani Yarubandi wrote:

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

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);
  

• }

should be 'else if', because TX and RX can't happen parallel.

• 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);

Wrt to current issue context it may be suffice to stop just DMA mode transfers but why not stop all mode of active transfer during shutdown in a generic way.

Regards,

Akash

• if (dma)

• geni_i2c_stop_xfer(gi2c);
  

• pm_runtime_put_sync_suspend(gi2c->se.dev);

+}

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

@@ -677,6 +719,7 @@ MODULE_DEVICE_TABLE(of, geni_i2c_dt_match); static struct platform_driver geni_i2c_driver = { .probe = geni_i2c_probe, .remove = geni_i2c_remove,

• .shutdown = geni_i2c_shutdown, .driver = { .name = "geni_i2c", .pm = &geni_i2c_pm_ops,

diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h index dd464943f717..c3c016496d98 100644 --- a/include/linux/qcom-geni-se.h +++ b/include/linux/qcom-geni-se.h @@ -77,6 +77,7 @@ struct geni_se { #define SE_DMA_RX_FSM_RST 0xd58 #define SE_HW_PARAM_0 0xe24 #define SE_HW_PARAM_1 0xe28 +#define SE_DMA_DEBUG_REG0 0xe40

/* GENI_FORCE_DEFAULT_REG fields */ #define FORCE_DEFAULT BIT(0) @@ -207,6 +208,10 @@ struct geni_se { #define RX_GENI_CANCEL_IRQ BIT(11) #define RX_GENI_GP_IRQ_EXT GENMASK(13, 12)

+/* SE_DMA_DEBUG_REG0 Register fields */ +#define DMA_TX_ACTIVE BIT(0) +#define DMA_RX_ACTIVE BIT(1)

• /* SE_HW_PARAM_0 fields */ #define TX_FIFO_WIDTH_MSK GENMASK(29, 24) #define TX_FIFO_WIDTH_SHFT 24