The current version checking mechanism works fine for DSI6G blocks. It
doesn't work so well for older generation DSIv2 blocks.
The initial read of REG_DSI_6G_HW_VERSION(offset 0x0) would result in a
read of REG_DSI_CTRL for DSIv2. This register won't necessarily be 0 on
DSIv2. It can be non zero if DSI was previously initialized by the
bootloader.
Instead of reading offset 0x0, we now read offset 0x1f0. For DSIv2, this
register is DSI_VERSION, and is bound to be non-zero. On DSI6G, this
register(offset 0x1f0) is SCRATCH_REGISTER_0, which no one ever seems to
touch, and from all register dumps I'vc seen, holds 0 all the time.
Modify dsi_get_version to read REG_DSI_VERSION to determine whether we
are DSI6G or DSIv2.
Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/dsi/dsi_host.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index aec97c8..7a365df 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -33,17 +33,24 @@
static int dsi_get_version(const void __iomem *base, u32 *major, u32 *minor)
{
u32 ver;
- u32 ver_6g;
if (!major || !minor)
return -EINVAL;
- /* From DSI6G(v3), addition of a 6G_HW_VERSION register at offset 0
+ /*
+ * From DSI6G(v3), addition of a 6G_HW_VERSION register at offset 0
* makes all other registers 4-byte shifted down.
+ *
+ * In order to identify between DSI6G(v3) and beyond, and DSIv2 and
+ * older, we read the DSI_VERSION register without any shift(offset
+ * 0x1f0). In the case of DSIv2, this hast to be a non-zero value. In
+ * the case of DSI6G, this has to be zero (the offset points to a
+ * scratch register which we never touch)
*/
- ver_6g = msm_readl(base + REG_DSI_6G_HW_VERSION);
- if (ver_6g == 0) {
- ver = msm_readl(base + REG_DSI_VERSION);
+
+ ver = msm_readl(base + REG_DSI_VERSION);
+ if (ver) {
+ /* older dsi host, there is no register shift */
ver = FIELD(ver, DSI_VERSION_MAJOR);
if (ver <= MSM_DSI_VER_MAJOR_V2) {
/* old versions */
@@ -54,12 +61,17 @@ static int dsi_get_version(const void __iomem *base, u32 *major, u32 *minor)
return -EINVAL;
}
} else {
+ /*
+ * newer host, offset 0 has 6G_HW_VERSION, the rest of the
+ * registers are shifted down, read DSI_VERSION again with
+ * the shifted offset
+ */
ver = msm_readl(base + DSI_6G_REG_SHIFT + REG_DSI_VERSION);
ver = FIELD(ver, DSI_VERSION_MAJOR);
if (ver == MSM_DSI_VER_MAJOR_6G) {
/* 6G version */
*major = ver;
- *minor = ver_6g;
+ *minor = msm_readl(base + REG_DSI_6G_HW_VERSION);
return 0;
} else {
return -EINVAL;
--
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