| Message ID | 20240930121601.172216-3-herve.codina@bootlin.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for the LAN966x PCI device using a DT overlay | expand |
Hi Herve, On Mon, 2024-09-30 at 14:15 +0200, Herve Codina wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you > know the content is safe > > In the LAN966x PCI device use case, syscon cannot be used as syscon > devices do not support removal [1]. A syscon device is a core > "system" > device and not a device available in some addon boards and so, it is > not > supposed to be removed. > > In order to remove the syscon usage, use a local mapping of a reg > address range when cpu-syscon is not present. > > Link: > https://lore.kernel.org/all/20240923100741.11277439@bootlin.com/ [1] > Signed-off-by: Herve Codina <herve.codina@bootlin.com> > --- > drivers/reset/reset-microchip-sparx5.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/reset/reset-microchip-sparx5.c > b/drivers/reset/reset-microchip-sparx5.c > index 636e85c388b0..1c095fa41d69 100644 > --- a/drivers/reset/reset-microchip-sparx5.c > +++ b/drivers/reset/reset-microchip-sparx5.c > @@ -114,8 +114,22 @@ static int mchp_sparx5_reset_probe(struct > platform_device *pdev) > return -ENOMEM; > > err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx- > >cpu_ctrl); > - if (err) > + switch (err) { > + case 0: > + break; > + case -ENODEV: > + /* > + * The cpu-syscon device is not available. > + * Fall back with IO mapping (i.e. mapping from reg > property). > + */ > + err = mchp_sparx5_map_io(pdev, 1, &ctx->cpu_ctrl); > + if (err) > + return err; > + break; > + default: > return err; > + } > + > err = mchp_sparx5_map_io(pdev, 0, &ctx->gcb_ctrl); > if (err) > return err; > -- > 2.46.1 > LGTM Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com> BR Steen
Hi Hervé, On Mon, Sep 30, 2024 at 2:16 PM Herve Codina <herve.codina@bootlin.com> wrote: > In the LAN966x PCI device use case, syscon cannot be used as syscon > devices do not support removal [1]. A syscon device is a core "system" > device and not a device available in some addon boards and so, it is not > supposed to be removed. > > In order to remove the syscon usage, use a local mapping of a reg > address range when cpu-syscon is not present. > > Link: https://lore.kernel.org/all/20240923100741.11277439@bootlin.com/ [1] > Signed-off-by: Herve Codina <herve.codina@bootlin.com> Thanks for your patch! > --- a/drivers/reset/reset-microchip-sparx5.c > +++ b/drivers/reset/reset-microchip-sparx5.c > @@ -114,8 +114,22 @@ static int mchp_sparx5_reset_probe(struct platform_device *pdev) > return -ENOMEM; > > err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx->cpu_ctrl); > - if (err) > + switch (err) { > + case 0: > + break; > + case -ENODEV: > + /* > + * The cpu-syscon device is not available. > + * Fall back with IO mapping (i.e. mapping from reg property). > + */ > + err = mchp_sparx5_map_io(pdev, 1, &ctx->cpu_ctrl); > + if (err) > + return err; > + break; > + default: > return err; > + } > + This can be shortened to: if (err == -ENODEV) { /* * The cpu-syscon device is not available. * Fall back with IO mapping (i.e. mapping from reg property). */ err = mchp_sparx5_map_io(pdev, 1, &ctx->cpu_ctrl); } if (err) return err; > err = mchp_sparx5_map_io(pdev, 0, &ctx->gcb_ctrl); > if (err) > return err; Gr{oetje,eeting}s, Geert
On Mon, Sep 30, 2024, at 12:15, Herve Codina wrote: > In the LAN966x PCI device use case, syscon cannot be used as syscon > devices do not support removal [1]. A syscon device is a core "system" > device and not a device available in some addon boards and so, it is not > supposed to be removed. > > In order to remove the syscon usage, use a local mapping of a reg > address range when cpu-syscon is not present. > > Link: https://lore.kernel.org/all/20240923100741.11277439@bootlin.com/ [1] > Signed-off-by: Herve Codina <herve.codina@bootlin.com> > --- >> err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx->cpu_ctrl); > - if (err) > + switch (err) { > + case 0: > + break; > + case -ENODEV: I was expecting a patch that would read the phandle and map the syscon node to keep the behavior unchanged, but I guess this one works as well. The downside of your approach is that it requires an different DT binding, which only works as long as there are no other users of the syscon registers. Arnd
On Mon, 30 Sep 2024 13:57:01 +0000 "Arnd Bergmann" <arnd@arndb.de> wrote: > On Mon, Sep 30, 2024, at 12:15, Herve Codina wrote: > > In the LAN966x PCI device use case, syscon cannot be used as syscon > > devices do not support removal [1]. A syscon device is a core "system" > > device and not a device available in some addon boards and so, it is not > > supposed to be removed. > > > > In order to remove the syscon usage, use a local mapping of a reg > > address range when cpu-syscon is not present. > > > > Link: https://lore.kernel.org/all/20240923100741.11277439@bootlin.com/ [1] > > Signed-off-by: Herve Codina <herve.codina@bootlin.com> > > --- > > >> err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx->cpu_ctrl); > > - if (err) > > + switch (err) { > > + case 0: > > + break; > > + case -ENODEV: > > I was expecting a patch that would read the phandle and map the > syscon node to keep the behavior unchanged, but I guess this one > works as well. > > The downside of your approach is that it requires an different > DT binding, which only works as long as there are no other > users of the syscon registers. Yes, I knwow but keeping the binding with the syscon device (i.e. compatible = "...", "syscon";) leads to confusion. Indeed, the syscon API cannot be used because using this API leads issues when the syscon device is removed. That means the you have a "syscon" node (compatible = "syscon") but we cannot use the syscon API (include/linux/mfd/syscon.h) with this node. Also, in order to share resources between several consumers of the "syscon" registers, we need exactly what is done in syscon. I mean we need to map resources only once, provide this resource throught a regmap an share this regmap between the consumers. Indeed a lock needs to be shared in order to protect against registers RMW accesses done by several consumers. In other word, we need to copy/paste syscon code with support for removal implemented (feature needed in the LAN966x PCI device use case). So, I found really simpler and less confusing to fully discard the syscon node and handle registers directly in the only one consumer. With all of these, do you thing my approach can be acceptable ? Best regards, Hervé
diff --git a/drivers/reset/reset-microchip-sparx5.c b/drivers/reset/reset-microchip-sparx5.c index 636e85c388b0..1c095fa41d69 100644 --- a/drivers/reset/reset-microchip-sparx5.c +++ b/drivers/reset/reset-microchip-sparx5.c @@ -114,8 +114,22 @@ static int mchp_sparx5_reset_probe(struct platform_device *pdev) return -ENOMEM; err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx->cpu_ctrl); - if (err) + switch (err) { + case 0: + break; + case -ENODEV: + /* + * The cpu-syscon device is not available. + * Fall back with IO mapping (i.e. mapping from reg property). + */ + err = mchp_sparx5_map_io(pdev, 1, &ctx->cpu_ctrl); + if (err) + return err; + break; + default: return err; + } + err = mchp_sparx5_map_io(pdev, 0, &ctx->gcb_ctrl); if (err) return err;
In the LAN966x PCI device use case, syscon cannot be used as syscon devices do not support removal [1]. A syscon device is a core "system" device and not a device available in some addon boards and so, it is not supposed to be removed. In order to remove the syscon usage, use a local mapping of a reg address range when cpu-syscon is not present. Link: https://lore.kernel.org/all/20240923100741.11277439@bootlin.com/ [1] Signed-off-by: Herve Codina <herve.codina@bootlin.com> --- drivers/reset/reset-microchip-sparx5.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)