[PATCH v4 04/14] drm/msm/a6xx: Extend and explain UBWC config

From: Konrad Dybcio
Date: Tue Mar 14 2023 - 11:29:04 EST


Rename lower_bit to hbb_lo and explain what it signifies.
Add explanations (wherever possible to other tunables).

Port setting min_access_length, ubwc_mode and hbb_hi from downstream.

Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
---
drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 39 +++++++++++++++++++++++++++--------
1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index a849db8252f2..2f55dac52833 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -786,10 +786,25 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
static void a6xx_set_ubwc_config(struct msm_gpu *gpu)
{
struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
- u32 lower_bit = 2;
- u32 amsbc = 0;
+ /* Unknown, introduced with A650 family, related to UBWC mode/ver 4 */
u32 rgb565_predicator = 0;
+ /* Unknown, introduced with A650 family */
u32 uavflagprd_inv = 0;
+ /* Whether the minimum access length is 64 bits */
+ u32 min_acc_len = 0;
+ /* Entirely magic, per-GPU-gen value */
+ u32 ubwc_mode = 0;
+ /*
+ * The Highest Bank Bit value represents the bit of the highest DDR bank.
+ * We then subtract 13 from it (13 is the minimum value allowed by hw) and
+ * write the lowest two bits of the remaining value as hbb_lo and the
+ * one above it as hbb_hi to the hardware. This should ideally use DRAM
+ * type detection.
+ */
+ u32 hbb_hi = 0;
+ u32 hbb_lo = 2;
+ /* Unknown, introduced with A640/680 */
+ u32 amsbc = 0;

/* a618 is using the hw default values */
if (adreno_is_a618(adreno_gpu))
@@ -800,25 +815,31 @@ static void a6xx_set_ubwc_config(struct msm_gpu *gpu)

if (adreno_is_a650(adreno_gpu) || adreno_is_a660(adreno_gpu)) {
/* TODO: get ddr type from bootloader and use 2 for LPDDR4 */
- lower_bit = 3;
+ hbb_lo = 3;
amsbc = 1;
rgb565_predicator = 1;
uavflagprd_inv = 2;
}

if (adreno_is_7c3(adreno_gpu)) {
- lower_bit = 1;
+ hbb_lo = 1;
amsbc = 1;
rgb565_predicator = 1;
uavflagprd_inv = 2;
}

gpu_write(gpu, REG_A6XX_RB_NC_MODE_CNTL,
- rgb565_predicator << 11 | amsbc << 4 | lower_bit << 1);
- gpu_write(gpu, REG_A6XX_TPL1_NC_MODE_CNTL, lower_bit << 1);
- gpu_write(gpu, REG_A6XX_SP_NC_MODE_CNTL,
- uavflagprd_inv << 4 | lower_bit << 1);
- gpu_write(gpu, REG_A6XX_UCHE_MODE_CNTL, lower_bit << 21);
+ rgb565_predicator << 11 | hbb_hi << 10 | amsbc << 4 |
+ min_acc_len << 3 | hbb_lo << 1 | ubwc_mode);
+
+ gpu_write(gpu, REG_A6XX_TPL1_NC_MODE_CNTL, hbb_hi << 4 |
+ min_acc_len << 3 | hbb_lo << 1 | ubwc_mode);
+
+ gpu_write(gpu, REG_A6XX_SP_NC_MODE_CNTL, hbb_hi << 10 |
+ uavflagprd_inv << 4 | min_acc_len << 3 |
+ hbb_lo << 1 | ubwc_mode);
+
+ gpu_write(gpu, REG_A6XX_UCHE_MODE_CNTL, min_acc_len << 23 | hbb_lo << 21);
}

static int a6xx_cp_init(struct msm_gpu *gpu)

--
2.39.2