mailbox: add MediaTek GPUEB IPI mailbox

The MT8196 SoC uses an embedded MCU to control frequencies and power of
the GPU. This controller is referred to as "GPUEB".

It communicates to the application processor, among other ways, through
a mailbox.

The mailbox exposes one interrupt, which appears to only be fired when a
response is received, rather than a transaction is completed. For us,
this means we unfortunately need to poll for txdone.

The mailbox also requires the EB clock to be on when touching any of the
mailbox registers.

Add a simple driver for it based on the common mailbox framework.

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 02432d4a5ccd..2016defda1fa 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -294,6 +294,16 @@ config MTK_CMDQ_MBOX
 	  critical time limitation, such as updating display configuration
 	  during the vblank.
 
+config MTK_GPUEB_MBOX
+	tristate "MediaTek GPUEB Mailbox Support"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	help
+	  The MediaTek GPUEB mailbox is used to communicate with the embedded
+	  controller in charge of GPU frequency and power management on some
+	  MediaTek SoCs, such as the MT8196.
+	  Say Y or m here if you want to support the MT8196 SoC in your kernel
+	  build.
+
 config ZYNQMP_IPI_MBOX
 	tristate "Xilinx ZynqMP IPI Mailbox"
 	depends on ARCH_ZYNQMP && OF