[PATCH v4] drm/etnaviv: add optional reset support

[LECOINTRE Philippe]

Add optional reset support which is mentioned in vivante,gc.yaml to
allow the driver to work on SoCs whose reset signal is asserted by default

Signed-off-by: Philippe Lecointre <philippe.lecoin...@thalesgroup.com>
Acked-by: Simon Lenain <simon.len...@thalesgroup.com>
---
v4:
- Rework to match feedback
---
 drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 41 +++++++++++++++++++++++++++
 drivers/gpu/drm/etnaviv/etnaviv_gpu.h |  2 ++
 2 files changed, 43 insertions(+)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c 
b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
index 2d4c112ce033..cf0d9049bcf1 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
@@ -13,6 +13,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 #include <linux/thermal.h>
 
 #include "etnaviv_cmdbuf.h"
@@ -172,6 +173,29 @@ int etnaviv_gpu_get_param(struct etnaviv_gpu *gpu, u32 
param, u64 *value)
        return 0;
 }
 
+static int etnaviv_gpu_reset_deassert(struct etnaviv_gpu *gpu)
+{
+       int ret;
+
+       /*
+        * 32 core clock cycles (slowest clock) required before deassertion
+        * 1 microsecond might match all implementations without computation
+        */
+       usleep_range(1, 2);
+
+       ret = reset_control_deassert(gpu->rst);
+       if (ret)
+               return ret;
+
+       /*
+        * 128 core clock cycles (slowest clock) required before any activity 
on AHB
+        * 1 microsecond might match all implementations without computation
+        */
+       usleep_range(1, 2);
+
+       return 0;
+}
+
 static inline bool etnaviv_is_model_rev(struct etnaviv_gpu *gpu, u32 model, 
u32 revision)
 {
        return gpu->identity.model == model &&
@@ -799,6 +823,12 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
                goto pm_put;
        }
 
+       ret = etnaviv_gpu_reset_deassert(gpu);
+       if (ret) {
+               dev_err(gpu->dev, "GPU reset deassert failed\n");
+               goto fail;
+       }
+
        etnaviv_hw_identify(gpu);
 
        if (gpu->identity.model == 0) {
@@ -1860,6 +1890,17 @@ static int etnaviv_gpu_platform_probe(struct 
platform_device *pdev)
        if (IS_ERR(gpu->mmio))
                return PTR_ERR(gpu->mmio);
 
+
+       /* Get Reset: */
+       gpu->rst = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+       if (IS_ERR(gpu->rst))
+               return dev_err_probe(dev, PTR_ERR(gpu->rst),
+                                    "failed to get reset\n");
+
+       err = reset_control_assert(gpu->rst);
+       if (err)
+               return dev_err_probe(dev, err, "failed to assert reset\n");
+
        /* Get Interrupt: */
        gpu->irq = platform_get_irq(pdev, 0);
        if (gpu->irq < 0)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h 
b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
index 4d8a7d48ade3..5cb46c84e03a 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
@@ -93,6 +93,7 @@ struct etnaviv_event {
 struct etnaviv_cmdbuf_suballoc;
 struct regulator;
 struct clk;
+struct reset_control;
 
 #define ETNA_NR_EVENTS 30
 
@@ -158,6 +159,7 @@ struct etnaviv_gpu {
        struct clk *clk_reg;
        struct clk *clk_core;
        struct clk *clk_shader;
+       struct reset_control *rst;
 
        unsigned int freq_scale;
        unsigned int fe_waitcycles;
-- 
2.19.1