bus: mhi: core: Offload register accesses to the controller

When reading or writing MHI registers, the core assumes that the physical
link is a memory mapped PCI link.  This assumption may not hold for all
MHI devices.  The controller knows what is the physical link (ie PCI, I2C,
SPI, etc), and therefore knows the proper methods to access that link.
The controller can also handle link specific error scenarios, such as
reading -1 when the PCI link went down.

Therefore, it is appropriate that the MHI core requests the controller to
make register accesses on behalf of the core, which abstracts the core
from link specifics, and end up removing an unnecessary assumption.

Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200430190555.32741-5-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index c80ba559face..84a6c9e72f52 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -342,6 +342,8 @@ struct mhi_controller_config {
  * @runtimet_put: CB function to decrement pm usage (required)
  * @map_single: CB function to create TRE buffer
  * @unmap_single: CB function to destroy TRE buffer
+ * @read_reg: Read a MHI register via the physical link (required)
+ * @write_reg: Write a MHI register via the physical link (required)
  * @buffer_len: Bounce buffer length
  * @bounce_buf: Use of bounce buffer
  * @fbc_download: MHI host needs to do complete image transfer (optional)
@@ -425,6 +427,10 @@ struct mhi_controller {
 			  struct mhi_buf_info *buf);
 	void (*unmap_single)(struct mhi_controller *mhi_cntrl,
 			     struct mhi_buf_info *buf);
+	int (*read_reg)(struct mhi_controller *mhi_cntrl, void __iomem *addr,
+			u32 *out);
+	void (*write_reg)(struct mhi_controller *mhi_cntrl, void __iomem *addr,
+			  u32 val);
 
 	size_t buffer_len;
 	bool bounce_buf;