Re: [PATCH v3 1/3] bus: mhi: core: Introduce internal register poll helper function

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On 2021-03-10 10:57 AM, Jeffrey Hugo wrote:
On 2/23/2021 8:44 PM, Bhaumik Bhatt wrote:
Introduce helper function to allow MHI core driver to poll for
a value in a register field. This helps reach a common path to
read and poll register values along with a retry time interval.

Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
---
  drivers/bus/mhi/core/internal.h |  3 +++
  drivers/bus/mhi/core/main.c     | 23 +++++++++++++++++++++++
  2 files changed, 26 insertions(+)

diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
index 6f80ec3..005286b 100644
--- a/drivers/bus/mhi/core/internal.h
+++ b/drivers/bus/mhi/core/internal.h
@@ -643,6 +643,9 @@ int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl, int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
  				    void __iomem *base, u32 offset, u32 mask,
  				    u32 shift, u32 *out);
+int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
+				    void __iomem *base, u32 offset, u32 mask,
+				    u32 shift, u32 val, u32 delayus);
void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
  		   u32 offset, u32 val);
void mhi_write_reg_field(struct mhi_controller *mhi_cntrl, void __iomem *base,
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 4e0131b..249ae26 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -4,6 +4,7 @@
   *
   */
  +#include <linux/delay.h>
  #include <linux/device.h>
  #include <linux/dma-direction.h>
  #include <linux/dma-mapping.h>
@@ -37,6 +38,28 @@ int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
  	return 0;
  }
+int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
+				    void __iomem *base, u32 offset,
+				    u32 mask, u32 shift, u32 val, u32 delayus)
+{
+	int ret = -ENOENT;
Make this int ret;
+	u32 out, retry = (mhi_cntrl->timeout_ms * 1000) / delayus;
+
+	while (retry--) {
+		ret = mhi_read_reg_field(mhi_cntrl, base, offset, mask, shift,
+					 &out);
+		if (ret)
+			return -EIO;

I generally dislike recoding return codes.  Do you believe it adds
value here?  I'm concerned that if I'm debugging an error, I'll get
EIO, which I trace to here, but then I don't know what the actual
error from mhi_read_reg_field() was.

Thanks for pointing out. I don't think its necessary to recode and I can go back to returning whatever the reg_field API returns. I have added the proposed changes here which help fix a potential bug that we'd return 0 if read is successful but
polling fails.
+
+		if (out == val)
+			return 0;
+
+		udelay(delayus);
+	}
+
+	return ret;
return -ENOENT; to signify failure to find the entry after poll duration completes
+}
+
void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
  		   u32 offset, u32 val)
  {


Thanks,
Bhaumik
---
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project



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