linux-kernel - Re: [PATCH net-next 14/15] net: sparx5: add compatible strings for lan969x and verify the target

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Message-ID: <20241023183301.5st3aa23ad6nl5xz@DEN-DL-M70577>
Date: Wed, 23 Oct 2024 18:33:01 +0000
From: Daniel Machon <daniel.machon@...rochip.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <andrew@...n.ch>, Lars Povlsen
	<lars.povlsen@...rochip.com>, Steen Hegelund <Steen.Hegelund@...rochip.com>,
	<horatiu.vultur@...rochip.com>, <jensemil.schulzostergaard@...rochip.com>,
	<Parthiban.Veerasooran@...rochip.com>, <Raju.Lakkaraju@...rochip.com>,
	<UNGLinuxDriver@...rochip.com>, Richard Cochran <richardcochran@...il.com>,
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, <jacob.e.keller@...el.com>,
	<ast@...erby.net>, <maxime.chevallier@...tlin.com>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next 14/15] net: sparx5: add compatible strings for
 lan969x and verify the target

> > Hi Krzysztof,
> >
> >>> Add compatible strings for the twelve lan969x SKU's (Stock Keeping Unit)
> >>> that we support, and verify that the devicetree target is supported by
> >>> the chip target.
> >>>
> >>> Each SKU supports different bandwidths and features (see [1] for
> >>> details). We want to be able to run a SKU with a lower bandwidth and/or
> >>> feature set, than what is supported by the actual chip. In order to
> >>> accomplish this we:
> >>>
> >>>     - add new field sparx5->target_dt that reflects the target from the
> >>>       devicetree (compatible string).
> >>>
> >>>     - compare the devicetree target with the actual chip target. If the
> >>>       bandwidth and features provided by the devicetree target is
> >>>       supported by the chip, we approve - otherwise reject.
> >>>
> >>>     - set the core clock and features based on the devicetree target
> >>>
> >>> [1] https://www.microchip.com/en-us/product/lan9698
> >>>
> >>> Reviewed-by: Steen Hegelund <Steen.Hegelund@...rochip.com>
> >>> Signed-off-by: Daniel Machon <daniel.machon@...rochip.com>
> >>> ---
> >>>  drivers/net/ethernet/microchip/sparx5/Makefile     |   1 +
> >>>  .../net/ethernet/microchip/sparx5/sparx5_main.c    | 194 ++++++++++++++++++++-
> >>>  .../net/ethernet/microchip/sparx5/sparx5_main.h    |   1 +
> >>>  3 files changed, 193 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/drivers/net/ethernet/microchip/sparx5/Makefile b/drivers/net/ethernet/microchip/sparx5/Makefile
> >>> index 3435ca86dd70..8fe302415563 100644
> >>> --- a/drivers/net/ethernet/microchip/sparx5/Makefile
> >>> +++ b/drivers/net/ethernet/microchip/sparx5/Makefile
> >>> @@ -19,3 +19,4 @@ sparx5-switch-$(CONFIG_DEBUG_FS) += sparx5_vcap_debugfs.o
> >>>  # Provide include files
> >>>  ccflags-y += -I$(srctree)/drivers/net/ethernet/microchip/vcap
> >>>  ccflags-y += -I$(srctree)/drivers/net/ethernet/microchip/fdma
> >>> +ccflags-y += -I$(srctree)/drivers/net/ethernet/microchip/lan969x
> >>> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> >>> index 5c986c373b3e..edbe639d98c5 100644
> >>> --- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> >>> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> >>> @@ -24,6 +24,8 @@
> >>>  #include <linux/types.h>
> >>>  #include <linux/reset.h>
> >>>
> >>> +#include "lan969x.h" /* lan969x_desc */
> >>> +
> >>>  #include "sparx5_main_regs.h"
> >>>  #include "sparx5_main.h"
> >>>  #include "sparx5_port.h"
> >>> @@ -227,6 +229,168 @@ bool is_sparx5(struct sparx5 *sparx5)
> >>>       }
> >>>  }
> >>>
> >>> +/* Set the devicetree target based on the compatible string */
> >>> +static int sparx5_set_target_dt(struct sparx5 *sparx5)
> >>> +{
> >>> +     struct device_node *node = sparx5->pdev->dev.of_node;
> >>> +
> >>> +     if (is_sparx5(sparx5))
> >>> +             /* For Sparx5 the devicetree target is always the chip target */
> >>> +             sparx5->target_dt = sparx5->target_ct;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9691-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9691VAO;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9692-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9692VAO;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9693-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9693VAO;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9694-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9694;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9695-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9694TSN;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9696-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9696;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9697-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9696TSN;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9698-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9698;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan9699-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9698TSN;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan969a-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9694RED;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan969b-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9696RED;
> >>> +     else if (of_device_is_compatible(node, "microchip,lan969c-switch"))
> >>> +             sparx5->target_dt = SPX5_TARGET_CT_LAN9698RED;
> >>> +     else
> >>> +             return -EINVAL;
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>> +/* Compare the devicetree target with the chip target.
> >>> + * Make sure the chip target supports the features and bandwidth requested
> >>> + * from the devicetree target.
> >>> + */
> >>> +static int sparx5_verify_target(struct sparx5 *sparx5)
> >>> +{
> >>> +     switch (sparx5->target_dt) {
> >>> +     case SPX5_TARGET_CT_7546:
> >>> +     case SPX5_TARGET_CT_7549:
> >>> +     case SPX5_TARGET_CT_7552:
> >>> +     case SPX5_TARGET_CT_7556:
> >>> +     case SPX5_TARGET_CT_7558:
> >>> +     case SPX5_TARGET_CT_7546TSN:
> >>> +     case SPX5_TARGET_CT_7549TSN:
> >>> +     case SPX5_TARGET_CT_7552TSN:
> >>> +     case SPX5_TARGET_CT_7556TSN:
> >>> +     case SPX5_TARGET_CT_7558TSN:
> >>> +             return 0;
> >>
> >> All this is weird. Why would you verify? You were matched, it cannot be
> >> mis-matching.
> >
> > We are verifying that the match (target/compatible string) from the
> > device tree is supported by the chip. Maybe I wasn't too clear about the
> > intend in v1.
> >
> > Each target supports different bandwidths and features. If you have a
> > lan9698 chip, it must, obviously, be possible to run it as a lan9698
> > target. However, some targets can be run on chip targets other than
> > themselves, given that the chip supports the bandwidth and features of
> > the provided target. In contrary, trying to run as a target with a
> > feature not supported by the chip, or a bandwidth higher than what the
> > chip supports, should be rejected.
> 
> But you are not supposed to compare DT with what you auto-detected.
> Detect your hardware, test if it is supported and then bail out.
> 
> None of above explains the code.
> 
> >
> > Without this logic, the chip id is read and a target is determined. That
> > means on a lan9698 chip you will always match the lan9698 target.
> 
> That's not the job of kernel.
> 
> >
> > With the new logic, it is possible to run as a different target than
> > what is read from the chip id, given that the target you are trying to
> > run as, is supported by the chip.
> 
> So just run on different target.
> 
> >
> >>
> >>> +     case SPX5_TARGET_CT_LAN9698RED:
> >>> +             if (sparx5->target_ct == SPX5_TARGET_CT_LAN9698RED)
> >>
> >> What is "ct"? sorry, all this code is a big no.
> >
> > In this case we were matched as a SPX5_TARGET_CT_LAN9698RED target. We
> > are verifying that the chip target (target_ct, which is read from the
> > chip) supports the target we were matched as.
> >
> >> Krzysztof
> >>
> >
> > This is a feature that we would like, as it gives the flexibility of
> > running different targets on the same chip. Now if this is something
> > that cannot be accepted, I will have to ditch this part.
> 
> I have no clue what the "target" is but so far it looks like you try to
> validate DT against detected device. That's not how it should work.

I will get rid of the verification in v2.

Thanks.

/Daniel

> 
> Best regards,
> Krzysztof
>