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Message-Id: <D4QI63B6YQU5.3UPKA7G75J445@bootlin.com>
Date: Tue, 08 Oct 2024 16:43:19 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Krzysztof Kozlowski" <krzk@...nel.org>
Cc: "Linus Walleij" <linus.walleij@...aro.org>, "Andi Shyti"
<andi.shyti@...nel.org>, "Rob Herring" <robh@...nel.org>, "Krzysztof
Kozlowski" <krzk+dt@...nel.org>, "Conor Dooley" <conor+dt@...nel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-i2c@...r.kernel.org>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Vladimir
Kondratiev" <vladimir.kondratiev@...ileye.com>,
Grégory Clement <gregory.clement@...tlin.com>, "Thomas
Petazzoni" <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
<tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH 2/4] i2c: nomadik: support Mobileye EyeQ6H I2C
controller
Hello Krzysztof,
On Tue Oct 8, 2024 at 3:39 PM CEST, Krzysztof Kozlowski wrote:
> On Tue, Oct 08, 2024 at 12:29:41PM +0200, Théo Lebrun wrote:
> > Add EyeQ6H support to the nmk-i2c AMBA driver. It shares the same quirk
> > as EyeQ5: the memory bus only supports 32-bit accesses. Avoid writeb()
> > and readb() by reusing the same `priv->has_32b_bus` flag.
> >
> > It does NOT need to write speed-mode specific value into a register;
> > therefore it does not depend on the mobileye,olb DT property.
> >
> > Refactoring is done using is_eyeq5 and is_eyeq6h boolean local
> > variables. Sort variables in reverse christmas tree to try and
> > introduce some logic into the ordering.
> >
> > Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> > ---
> > drivers/i2c/busses/i2c-nomadik.c | 22 +++++++++++-----------
> > 1 file changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
> > index ad0f02acdb1215a1c04729f97bb14a4d93f88456..ea511d3a58073eaedb63850026e05b59427a69c6 100644
> > --- a/drivers/i2c/busses/i2c-nomadik.c
> > +++ b/drivers/i2c/busses/i2c-nomadik.c
> > @@ -6,10 +6,10 @@
> > * I2C master mode controller driver, used in Nomadik 8815
> > * and Ux500 platforms.
> > *
> > - * The Mobileye EyeQ5 platform is also supported; it uses
> > + * The Mobileye EyeQ5 and EyeQ6H platforms are also supported; they use
> > * the same Ux500/DB8500 IP block with two quirks:
> > * - The memory bus only supports 32-bit accesses.
> > - * - A register must be configured for the I2C speed mode;
> > + * - (only EyeQ5) A register must be configured for the I2C speed mode;
> > * it is located in a shared register region called OLB.
> > *
> > * Author: Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>
> > @@ -1046,8 +1046,6 @@ static int nmk_i2c_eyeq5_probe(struct nmk_i2c_dev *priv)
> > struct regmap *olb;
> > unsigned int id;
> >
> > - priv->has_32b_bus = true;
> > -
> > olb = syscon_regmap_lookup_by_phandle_args(np, "mobileye,olb", 1, &id);
> > if (IS_ERR(olb))
> > return PTR_ERR(olb);
> > @@ -1070,13 +1068,15 @@ static int nmk_i2c_eyeq5_probe(struct nmk_i2c_dev *priv)
> >
> > static int nmk_i2c_probe(struct amba_device *adev, const struct amba_id *id)
> > {
> > - int ret = 0;
> > - struct nmk_i2c_dev *priv;
> > - struct device_node *np = adev->dev.of_node;
> > - struct device *dev = &adev->dev;
> > - struct i2c_adapter *adap;
> > struct i2c_vendor_data *vendor = id->data;
> > + struct device_node *np = adev->dev.of_node;
> > + bool is_eyeq6h = of_device_is_compatible(np, "mobileye,eyeq6h-i2c");
> > + bool is_eyeq5 = of_device_is_compatible(np, "mobileye,eyeq5-i2c");
>
> You should use match data, not add compatibles in the middle of code.
> That's preferred, scallable pattern. What you added here last time does
> not scale and above change is a proof for that.
I would have used match data if the driver struct had a .of_match_table
field. `struct amba_driver` does not. Are you recommending the approach
below?
I don't see how it brings much to the driver but I do get the scaling
issue as the number of support compatibles increases. This is a fear
based on what *could* happen in the future though.
------------------------------------------------------------------------
diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
index 82571983bbca..98fc40dfcbfc 100644
--- a/drivers/i2c/busses/i2c-nomadik.c
+++ b/drivers/i2c/busses/i2c-nomadik.c
@@ -26,6 +26,7 @@
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
+#include <linux/of_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
@@ -1061,28 +1062,46 @@ static int nmk_i2c_eyeq5_probe(struct nmk_i2c_dev *priv)
return 0;
}
+#define NMK_I2C_EYEQ_FLAG_32B_BUS BIT(0)
+#define NMK_I2C_EYEQ_FLAG_IS_EYEQ5 BIT(1)
+
+static const struct of_device_id nmk_i2c_eyeq_match_table[] = {
+ {
+ .compatible = "mobileye,eyeq5-i2c",
+ .data = (void*)(NMK_I2C_EYEQ_FLAG_32B_BUS | NMK_I2C_EYEQ_FLAG_IS_EYEQ5),
+ },
+ {
+ .compatible = "mobileye,eyeq6h-i2c",
+ .data = (void*)(NMK_I2C_EYEQ_FLAG_32B_BUS),
+ },
+};
+
static int nmk_i2c_probe(struct amba_device *adev, const struct amba_id *id)
{
struct i2c_vendor_data *vendor = id->data;
struct device_node *np = adev->dev.of_node;
- bool is_eyeq6h = of_device_is_compatible(np, "mobileye,eyeq6h-i2c");
- bool is_eyeq5 = of_device_is_compatible(np, "mobileye,eyeq5-i2c");
u32 max_fifo_threshold = (vendor->fifodepth / 2) - 1;
+ const struct of_device_id *match;
struct device *dev = &adev->dev;
+ unsigned long match_flags = 0;
struct nmk_i2c_dev *priv;
struct i2c_adapter *adap;
int ret = 0;
+ match = of_match_device(nmk_i2c_eyeq_match_table, dev);
+ if (match)
+ match_flags = (unsigned long)match->data;
+
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->vendor = vendor;
priv->adev = adev;
- priv->has_32b_bus = is_eyeq5 || is_eyeq6h;
+ priv->has_32b_bus = match_flags & NMK_I2C_EYEQ_FLAG_32B_BUS;
nmk_i2c_of_probe(np, priv);
- if (is_eyeq5) {
+ if (match_flags & NMK_I2C_EYEQ_FLAG_IS_EYEQ5) {
ret = nmk_i2c_eyeq5_probe(priv);
if (ret)
return dev_err_probe(dev, ret, "failed OLB lookup\n");
------------------------------------------------------------------------
Thanks Krzysztof,
--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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