Re: [PATCH v2 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing between two subsystems

From: Mukesh Kumar Savaliya
Date: Tue Sep 10 2024 - 05:15:51 EST

Hi Neil,

On 9/9/2024 6:34 PM, neil.armstrong@xxxxxxxxxx wrote:
On 09/09/2024 11:18, Mukesh Kumar Savaliya wrote:
Hi Neil,

On 9/9/2024 2:24 PM, neil.armstrong@xxxxxxxxxx wrote:
Hi,

On 06/09/2024 21:14, Mukesh Kumar Savaliya wrote:
Add support to share I2C SE by two Subsystems in a mutually exclusive way.
Use  "qcom,shared-se" flag in a particular i2c instance node if the
usecase requires i2c controller to be shared.

I2C driver just need to mark first_msg and last_msg flag to help indicate
GPI driver to  take lock and unlock TRE there by protecting from concurrent
access from other EE or Subsystem.

gpi_create_i2c_tre() function at gpi.c will take care of adding Lock and
Unlock TRE for the respective transfer operations.

Since the GPIOs are also shared for the i2c bus between two SS, do not
touch GPIO configuration during runtime suspend and only turn off the
clocks. This will allow other SS to continue to transfer the data
without any disturbance over the IO lines.

This doesn't answer my question about what would be the behavior if one
use uses, for example, GPI DMA, and the Linux kernel FIFO mode or SE DMA ?

Shared usecase is not supported for non GSI mode (FIFO and DMA), it should be static usecase. Dynamic sharing from two clients of two subsystems is only for GSI mode. Hope this helps ?

Sure, this is why I proposed on v1 cover letter reply to add:
Sure, i will add in cover letter and code check combining with fifo_disable check.
==============><=====================================================================
diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index ee2e431601a6..a15825ea56de 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -885,7 +885,7 @@ static int geni_i2c_probe(struct platform_device *pdev)
         else
                 fifo_disable = readl_relaxed(gi2c->se.base + GENI_IF_DISABLE_RO) & FIFO_IF_DISABLE;

-       if (fifo_disable) {
+       if (gi2c->is_shared || fifo_disable) {
Should be ANDING logically, as we need to combine both check. Shared
usecase possible only for fifo_disable.

if(gi2c->is_shared && fifo_disable) {
                 /* FIFO is disabled, so we can only use GPI DMA */
                 gi2c->gpi_mode = true;
                 ret = setup_gpi_dma(gi2c);
==============><=====================================================================

Thanks,
Neil

Because it seems to "fix" only the GPI DMA shared case.

Neil


Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@xxxxxxxxxxx>
---
  drivers/i2c/busses/i2c-qcom-geni.c | 29 ++++++++++++++++++++++-------
  1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index eebb0cbb6ca4..ee2e431601a6 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -1,5 +1,6 @@
  // SPDX-License-Identifier: GPL-2.0
  // Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
+// Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
  #include <linux/acpi.h>
  #include <linux/clk.h>
@@ -99,6 +100,7 @@ struct geni_i2c_dev {
      struct dma_chan *rx_c;
      bool gpi_mode;
      bool abort_done;
+    bool is_shared;
  };
  struct geni_i2c_desc {
@@ -602,6 +604,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
      peripheral.clk_div = itr->clk_div;
      peripheral.set_config = 1;
      peripheral.multi_msg = false;
+    peripheral.shared_se = gi2c->is_shared;
      for (i = 0; i < num; i++) {
          gi2c->cur = &msgs[i];
@@ -612,6 +615,8 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
          if (i < num - 1)
              peripheral.stretch = 1;
+        peripheral.first_msg = (i == 0);
+        peripheral.last_msg = (i == num - 1);
          peripheral.addr = msgs[i].addr;
          ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
@@ -631,8 +636,11 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
          dma_async_issue_pending(gi2c->tx_c);
          time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
-        if (!time_left)
+        if (!time_left) {
+            dev_err(gi2c->se.dev, "I2C timeout gpi flags:%d addr:0x%x\n",
+                        gi2c->cur->flags, gi2c->cur->addr);
              gi2c->err = -ETIMEDOUT;
+        }
          if (gi2c->err) {
              ret = gi2c->err;
@@ -800,6 +808,11 @@ static int geni_i2c_probe(struct platform_device *pdev)
          gi2c->clk_freq_out = KHZ(100);
      }
+    if (of_property_read_bool(pdev->dev.of_node, "qcom,shared-se")) {
+        gi2c->is_shared = true;
+        dev_dbg(&pdev->dev, "Shared SE Usecase\n");
+    }
+
      if (has_acpi_companion(dev))
          ACPI_COMPANION_SET(&gi2c->adap.dev, ACPI_COMPANION(dev));
@@ -962,14 +975,16 @@ static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
      struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
      disable_irq(gi2c->irq);
-    ret = geni_se_resources_off(&gi2c->se);
-    if (ret) {
-        enable_irq(gi2c->irq);
-        return ret;
-
+    if (gi2c->is_shared) {
+        geni_se_clks_off(&gi2c->se);
      } else {
-        gi2c->suspended = 1;
+        ret = geni_se_resources_off(&gi2c->se);
+        if (ret) {
+            enable_irq(gi2c->irq);
+            return ret;
+        }
      }
+    gi2c->suspended = 1;
      clk_disable_unprepare(gi2c->core_clk);