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@codeaurora.org --- 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 4c49868..8e8fcc7 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;