Change in coreboot[master]: device/azalia_device.c: Add option to lock down GCAP

[Angel Pons (Code Review)]

Angel Pons has submitted this change. ( https://review.coreboot.org/c/coreboot/+/50794 )

Change subject: device/azalia_device.c: Add option to lock down GCAP
......................................................................

device/azalia_device.c: Add option to lock down GCAP

On Intel 6-series PCHs, the GCAP register is R/WO (Read / Write Once),
and needs to be written to after the HD Audio controller is taken out
of reset. Add a Kconfig option to read and write back GCAP in order to
lock it down. Follow-up commits will select this option when switching
platforms to use common Azalia code, to preserve original behaviour.

Change-Id: I70bab20816fb6c0bf7bff35c3d2f5828cd96172d
Signed-off-by: Patrick Rudolph 
Signed-off-by: Angel Pons 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50794
Tested-by: build bot (Jenkins) 
Reviewed-by: Arthur Heymans 
---
M src/device/Kconfig
M src/device/azalia_device.c
2 files changed, 14 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved

diff --git a/src/device/Kconfig b/src/device/Kconfig
index 63b7d6c..5ae3466 100644
--- a/src/device/Kconfig
+++ b/src/device/Kconfig
@@ -527,6 +527,15 @@
    help
      The maximum number of codecs supported on a single HD Audio controller.

+config AZALIA_LOCK_DOWN_R_WO_GCAP
+	def_bool n
+	depends on AZALIA_PLUGIN_SUPPORT
+	help
+	  The GCAP register is implemented as R/WO (Read / Write Once) on some
+	  HD Audio controllers, such as Intel 6-series PCHs. Select this option
+	  to lock down the GCAP register after deasserting the controller reset
+	  bit. Locking is done by reading GCAP and writing back the read value.
+
 config PCIEXP_PLUGIN_SUPPORT
    bool
    default y
diff --git a/src/device/azalia_device.c b/src/device/azalia_device.c
index 013a49a..9202f72 100644
--- a/src/device/azalia_device.c
+++ b/src/device/azalia_device.c
@@ -56,6 +56,11 @@
    if (azalia_exit_reset(base) < 0)
    	goto no_codec;

+	if (CONFIG(AZALIA_LOCK_DOWN_R_WO_GCAP)) {
+		/* If GCAP is R/WO, lock it down after deasserting controller reset */
+		write16(base + HDA_GCAP_REG, read16(base + HDA_GCAP_REG));
+	}
+
    /* clear STATESTS bits (BAR + 0xe)[2:0] */
    reg16 = read16(base + HDA_STATESTS_REG);
    reg16 |= codec_mask;