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Date: Thu, 22 Jun 2023 14:23:39 +0200
From: Markus Schneider-Pargmann <msp@...libre.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Wolfgang Grandegger <wg@...ndegger.com>,
Marc Kleine-Budde <mkl@...gutronix.de>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Conor Dooley <conor+dt@...nel.org>,
Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
Michal Kubiak <michal.kubiak@...el.com>,
Vivek Yadav <vivek.2311@...sung.com>, linux-can@...r.kernel.org,
netdev@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH v2 5/6] can: tcan4x5x: Add support for tcan4552/4553
Hi Krzysztof,
On Wed, Jun 21, 2023 at 03:00:39PM +0200, Krzysztof Kozlowski wrote:
> On 21/06/2023 14:31, Markus Schneider-Pargmann wrote:
> > Hi Krzysztof,
> >
> > On Wed, Jun 21, 2023 at 12:28:34PM +0200, Krzysztof Kozlowski wrote:
> >> On 21/06/2023 11:31, Markus Schneider-Pargmann wrote:
> >>> tcan4552 and tcan4553 do not have wake or state pins, so they are
> >>> currently not compatible with the generic driver. The generic driver
> >>> uses tcan4x5x_disable_state() and tcan4x5x_disable_wake() if the gpios
> >>> are not defined. These functions use register bits that are not
> >>> available in tcan4552/4553.
> >>>
> >>> This patch adds support by introducing version information to reflect if
> >>> the chip has wake and state pins. Also the version is now checked.
> >>>
> >>> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> >>> ---
> >>> drivers/net/can/m_can/tcan4x5x-core.c | 128 +++++++++++++++++++++-----
> >>> 1 file changed, 104 insertions(+), 24 deletions(-)
> >>>
> >>> diff --git a/drivers/net/can/m_can/tcan4x5x-core.c b/drivers/net/can/m_can/tcan4x5x-core.c
> >>> index fb9375fa20ec..756acd122075 100644
> >>> --- a/drivers/net/can/m_can/tcan4x5x-core.c
> >>> +++ b/drivers/net/can/m_can/tcan4x5x-core.c
> >>> @@ -7,6 +7,7 @@
> >>> #define TCAN4X5X_EXT_CLK_DEF 40000000
> >>>
> >>> #define TCAN4X5X_DEV_ID1 0x00
> >>> +#define TCAN4X5X_DEV_ID1_TCAN 0x4e414354 /* ASCII TCAN */
> >>> #define TCAN4X5X_DEV_ID2 0x04
> >>> #define TCAN4X5X_REV 0x08
> >>> #define TCAN4X5X_STATUS 0x0C
> >>> @@ -103,6 +104,13 @@
> >>> #define TCAN4X5X_WD_3_S_TIMER BIT(29)
> >>> #define TCAN4X5X_WD_6_S_TIMER (BIT(28) | BIT(29))
> >>>
> >>> +struct tcan4x5x_version_info {
> >>> + u32 id2_register;
> >>> +
> >>> + bool has_wake_pin;
> >>> + bool has_state_pin;
> >>> +};
> >>> +
> >>> static inline struct tcan4x5x_priv *cdev_to_priv(struct m_can_classdev *cdev)
> >>> {
> >>> return container_of(cdev, struct tcan4x5x_priv, cdev);
> >>> @@ -254,18 +262,68 @@ static int tcan4x5x_disable_state(struct m_can_classdev *cdev)
> >>> TCAN4X5X_DISABLE_INH_MSK, 0x01);
> >>> }
> >>>
> >>> -static int tcan4x5x_get_gpios(struct m_can_classdev *cdev)
> >>> +static const struct tcan4x5x_version_info tcan4x5x_generic;
> >>> +static const struct of_device_id tcan4x5x_of_match[];
> >>> +
> >>> +static const struct tcan4x5x_version_info
> >>> +*tcan4x5x_find_version_info(struct tcan4x5x_priv *priv, u32 id2_value)
> >>> +{
> >>> + for (int i = 0; tcan4x5x_of_match[i].data; ++i) {
> >>> + const struct tcan4x5x_version_info *vinfo =
> >>> + tcan4x5x_of_match[i].data;
> >>> + if (!vinfo->id2_register || id2_value == vinfo->id2_register) {
> >>> + dev_warn(&priv->spi->dev, "TCAN device is %s, please use it in DT\n",
> >>> + tcan4x5x_of_match[i].compatible);
> >>> + return vinfo;
> >>> + }
> >>> + }
> >>> +
> >>> + return &tcan4x5x_generic;
> >>
> >> I don't understand what do you want to achieve here. Kernel job is not
> >> to validate DTB, so if DTB says you have 4552, there is no need to
> >> double check. On the other hand, you have Id register so entire idea of
> >> custom compatibles can be dropped and instead you should detect the
> >> variant based on the ID.
> >
> > I can read the ID register but tcan4552 and 4553 do not have two
> > devicetree properties that tcan4550 has, namely state and wake gpios.
>
> Does not matter, you don't use OF matching to then differentiate
> handling of GPIOs to then read the register. You first read registers,
> so everything is auto-detectable.
>
> > See v1 discussion about that [1].
>
> Yeah, but your code is different, although maybe we just misunderstood
> each other. You wrote that you cannot use the GPIOs, so I assumed you
> need to know the variant before using the GPIOs. Then you need
> compatibles. It's not the case here. You can read the variant and based
> on this skip entirely GPIOs as they are entirely missing.
The version information is always readable for that chip, regardless of
state and wake GPIOs as far as I know. So yes it is possible to setup
the GPIOs based on the content of the ID register.
I personally would prefer separate compatibles. The binding
documentation needs to address that wake and state GPIOs are not
available for tcan4552/4553. I think having compatibles that are for
these chips would make sense then. However this is my opinion, you are
the maintainer.
Best,
Markus
>
> >
> > In v1 Marc pointed out that mcp251xfd is using an autodetection and warn
> > mechanism which I implemented here as well. [2]
>
> But why? Just read the ID and detect the variant based on this. Your DT
> still can have separate compatibles followed by fallback, that's not a
> problem.
>
>
> Best regards,
> Krzysztof
>
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