On 2/26/2024 4:02 PM, Mukesh Ojha wrote:
On 2/22/2024 11:37 PM, Sahil Chandna wrote:
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
I was trying to avoid two parallel call from llcc_slice_getd() calling
parallel call to of_find_node_by_name() as it should be one time search
for device presence to find a node and check if device is present or
not.
-Mukesh
Got it, but of_find_node_by_name () is holding a raw_spin_lock_irqsave
() for concurrency, right ? please correct me if understanding is wrong.
+
+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))
Also, thinking about this, should the status of device present or not be
saved in static variable instead of function call for each client ?
return ERR_CAST(drv_data);
cfg = drv_data->cfg;
Regards,
Sahil
