Patch "accel/qaic: Implement quirk for SOC_HW_VERSION" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    accel/qaic: Implement quirk for SOC_HW_VERSION

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     accel-qaic-implement-quirk-for-soc_hw_version.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c745226221609caebb9e68d1a19e76e74f1bae26
Author: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
Date:   Fri Dec 8 09:31:01 2023 -0700

    accel/qaic: Implement quirk for SOC_HW_VERSION
    
    [ Upstream commit 4c8874c2a6512b9fe7285cab1a6910d9211a6cfb ]
    
    The SOC_HW_VERSION register in the BHI space is not correctly initialized
    by the device and in many cases contains uninitialized data. The register
    could contain 0xFFFFFFFF which is a special value to indicate a link
    error in PCIe, therefore if observed, we could incorrectly think the
    device is down.
    
    Intercept reads for this register, and provide the correct value - every
    production instance would read 0x60110200 if the device was operating as
    intended.
    
    Fixes: a36bf7af868b ("accel/qaic: Add MHI controller")
    Signed-off-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
    Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@xxxxxxxxxxx>
    Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@xxxxxxxxxxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/20231208163101.1295769-3-quic_jhugo@xxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/accel/qaic/mhi_controller.c b/drivers/accel/qaic/mhi_controller.c
index 5036e58e7235b..1405623b03e4e 100644
--- a/drivers/accel/qaic/mhi_controller.c
+++ b/drivers/accel/qaic/mhi_controller.c
@@ -404,8 +404,21 @@ static struct mhi_controller_config aic100_config = {
 
 static int mhi_read_reg(struct mhi_controller *mhi_cntrl, void __iomem *addr, u32 *out)
 {
-	u32 tmp = readl_relaxed(addr);
+	u32 tmp;
 
+	/*
+	 * SOC_HW_VERSION quirk
+	 * The SOC_HW_VERSION register (offset 0x224) is not reliable and
+	 * may contain uninitialized values, including 0xFFFFFFFF. This could
+	 * cause a false positive link down error.  Instead, intercept any
+	 * reads and provide the correct value of the register.
+	 */
+	if (addr - mhi_cntrl->regs == 0x224) {
+		*out = 0x60110200;
+		return 0;
+	}
+
+	tmp = readl_relaxed(addr);
 	if (tmp == U32_MAX)
 		return -EIO;