Re: [PATCH] soc: qcom: llcc: Add llcc device availability check

From: Sahil Chandna
Date: Thu Feb 22 2024 - 13:08:21 EST


On 2/20/2024 5:58 PM, Mukesh Ojha wrote:
When llcc driver is enabled and llcc device is not
physically there on the SoC, client can get
-EPROBE_DEFER on calling llcc_slice_getd() and it
is possible they defer forever.

Let's add a check device availabilty and set the
appropriate applicable error in drv_data.

Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
---
drivers/soc/qcom/llcc-qcom.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
index 4ca88eaebf06..cb336b183bba 100644
--- a/drivers/soc/qcom/llcc-qcom.c
+++ b/drivers/soc/qcom/llcc-qcom.c
@@ -769,6 +769,27 @@ static const struct qcom_sct_config x1e80100_cfgs = {
};
static struct llcc_drv_data *drv_data = (void *) -EPROBE_DEFER;
+static DEFINE_MUTEX(dev_avail);
what is the requirement for mutex lock here? Since we are only trying to find if node present or not
+
+static bool is_llcc_device_available(void)
+{
+ static struct llcc_drv_data *ptr;
+
+ mutex_lock(&dev_avail);
+ if (!ptr) {
+ struct device_node *node;
+
+ node = of_find_node_by_name(NULL, "system-cache-controller");
+ if (!of_device_is_available(node)) {
+ pr_warn("llcc-qcom: system-cache-controller node not found\n");
+ drv_data = ERR_PTR(-ENODEV);
+ }
+ of_node_put(node);
+ ptr = drv_data;
+ }
+ mutex_unlock(&dev_avail);
+ return (PTR_ERR(ptr) != -ENODEV) ? true : false;
+}
/**
* llcc_slice_getd - get llcc slice descriptor
@@ -783,7 +804,7 @@ struct llcc_slice_desc *llcc_slice_getd(u32 uid)
struct llcc_slice_desc *desc;
u32 sz, count;
- if (IS_ERR(drv_data))
+ if (!is_llcc_device_available() || IS_ERR(drv_data))
return ERR_CAST(drv_data);
cfg = drv_data->cfg;