Re: [PATCH v4 3/5] nvmem: core: Add consumer API to get nvmem cell from node
From: Srinivas Kandagatla
Date: Fri Jul 08 2016 - 13:24:08 EST
On 08/07/16 17:42, Stefan Agner wrote:
On 2016-07-08 08:41, Srinivas Kandagatla wrote:
On 07/07/16 14:48, maitysanchayan@xxxxxxxxx wrote:
Hello Srinivas,
On 16-07-07 1
...
Our requirement is to be able to pass the soc node pointer and then
be able to get a nvmem cell by specifying it's name. So for our case
Why?
Sorry for not providing the background directly. The patches before this
series used that approach. In the previous discussions it has been pointed
out that it is not acceptable to have additional device tree bindings for
providing data that the driver wants at the SoC node level or to have bindings
just for the SoC bus driver alone since we aren't really describing the
hardware.
SOC driver seems to search for an arbitrary node by its name, which is
not a binding and can break anytime in cases If the scope of nvmem
provider is out of soc node or if the nvmem cells are not named as
expected. That looks very fragile.
In that case, that just "won't happen" because the soc driver is a very
soc specific driver only used for this device tree. We it will always
bind to that high level soc node.
If the soc node is actual consumer of nvmem cells, I see no reason why
we should not use proper nvmem bindings?
There is a reason: We don't describe the hardware with it...
The cfg0/cfg1 register which Sanchayan needs to read in the soc bus
driver are just two register with a unique ID of the SoC. In whatever
"Unique ID of the SOC" doesn't this mean that its a part of soc hw
description/configuration/setup?
Am still not clear why this setup any different to other use cases like
mac address/calibration data?
I still feel that this should be described in the DT.
Rob,
What do you think?
driver throughout the system we use that ID (e.g. in a random generator
for initialization) we never describe an actual hardware relation... Its
just software and how we use that unique ID. The device tree is ment to
describe hardware. Hence the NVMEM consumer binding is not suited for
such NVMEM cells...
By describing the NVMEM cells location in device tree (producer API, the
NVMEM cells are in hardware at that location, so using the device tree
for that part is fine) and hard coding the NVMEM cell we need in the
driver code we don't violate the device tree matra "describe the
hardware"...
IMHO, We should indeed describe the SOC hardware and its relationship
w.r.t to nvmem provider in device tree. Reasoning being these both are
some form of IP blocks/hw which depend on each other.
Looking-up the nodes direcly is what Rob suggested here:
https://lkml.org/lkml/2016/5/23/573
I did read this, I was not convinced that we should do a direct lookup
for nvmem cells.
thanks,
srini
Given the fact that the patch is potentially bypassing the nvmem
bindings, am not happy to take it!
If you can provide a solution acceptable by the device tree folks and
works without this patch, I am happy to do it...
Btw, I am not entirely happy with the API name, but did not had a better
idea... And we we should probably add a note that the device tree
consumer binding is the preferred way to do it.
--
Stefan
thanks,
srini
For the discussion,
https://lkml.org/lkml/2016/5/23/573
https://lkml.org/lkml/2016/5/2/71
Regards,
Sanchayan.
ocotp node has cfg0 and cfg1 which we want but we cannot use existing
nvmem consumer API since that requires having the nvmem consumer properties
in the node we are binding to viz. is a direct nvmem consumer.
Regards,
Sanchayan.
thanks,
srini
Parent node can also be the of_node of the main SoC device
node.
Signed-off-by: Sanchayan Maity <maitysanchayan@xxxxxxxxx>
---
drivers/nvmem/core.c | 44 +++++++++++++++++++++++++++++-------------
include/linux/nvmem-consumer.h | 1 +
2 files changed, 32 insertions(+), 13 deletions(-)
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 965911d..470abee 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -743,29 +743,21 @@ static struct nvmem_cell *nvmem_cell_get_from_list(const char *cell_id)
#if IS_ENABLED(CONFIG_NVMEM) && IS_ENABLED(CONFIG_OF)
/**
- * of_nvmem_cell_get() - Get a nvmem cell from given device node and cell id
+ * of_nvmem_cell_get_direct() - Get a nvmem cell from given device node
*
- * @dev node: Device tree node that uses the nvmem cell
- * @id: nvmem cell name from nvmem-cell-names property.
+ * @dev node: Device tree node that uses nvmem cell
*
* Return: Will be an ERR_PTR() on error or a valid pointer
* to a struct nvmem_cell. The nvmem_cell will be freed by the
* nvmem_cell_put().
*/
-struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
- const char *name)
+struct nvmem_cell *of_nvmem_cell_get_direct(struct device_node *cell_np)
{
- struct device_node *cell_np, *nvmem_np;
+ struct device_node *nvmem_np;
struct nvmem_cell *cell;
struct nvmem_device *nvmem;
const __be32 *addr;
- int rval, len, index;
-
- index = of_property_match_string(np, "nvmem-cell-names", name);
-
- cell_np = of_parse_phandle(np, "nvmem-cells", index);
- if (!cell_np)
- return ERR_PTR(-EINVAL);
+ int rval, len;
nvmem_np = of_get_next_parent(cell_np);
if (!nvmem_np)
@@ -824,6 +816,32 @@ err_mem:
return ERR_PTR(rval);
}
+EXPORT_SYMBOL_GPL(of_nvmem_cell_get_direct);
+
+/**
+ * of_nvmem_cell_get() - Get a nvmem cell from given device node and cell id
+ *
+ * @dev node: Device tree node that uses the nvmem cell
+ * @id: nvmem cell name from nvmem-cell-names property.
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer
+ * to a struct nvmem_cell. The nvmem_cell will be freed by the
+ * nvmem_cell_put().
+ */
+struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
+ const char *name)
+{
+ struct device_node *cell_np;
+ int index;
+
+ index = of_property_match_string(np, "nvmem-cell-names", name);
+
+ cell_np = of_parse_phandle(np, "nvmem-cells", index);
+ if (!cell_np)
+ return ERR_PTR(-EINVAL);
+
+ return of_nvmem_cell_get_direct(cell_np);
+}
EXPORT_SYMBOL_GPL(of_nvmem_cell_get);
#endif
diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
index 9bb77d3..bf879fc 100644
--- a/include/linux/nvmem-consumer.h
+++ b/include/linux/nvmem-consumer.h
@@ -136,6 +136,7 @@ static inline int nvmem_device_write(struct nvmem_device *nvmem,
#endif /* CONFIG_NVMEM */
#if IS_ENABLED(CONFIG_NVMEM) && IS_ENABLED(CONFIG_OF)
+struct nvmem_cell *of_nvmem_cell_get_direct(struct device_node *cell_np);
struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
const char *name);
struct nvmem_device *of_nvmem_device_get(struct device_node *np,