| Message ID | 20210519080436.18975-1-jamin_lin@aspeedtech.com |
|---|---|
| Headers | show |
| Series | i2c: aspeed: avoid new registers definition of AST2600 | expand |
On Wed, 19 May 2021 16:04:29 +0800, Jamin Lin wrote: > Add global-reg node for AST2600. Document the properties for > "aspeed,ast2600-i2c-global" compatible node. > > Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > --- > .../devicetree/bindings/i2c/aspeed,i2c.yaml | 89 +++++++++++++++++++ > .../devicetree/bindings/i2c/i2c-aspeed.txt | 49 ---------- > 2 files changed, 89 insertions(+), 49 deletions(-) > create mode 100644 Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > delete mode 100644 Documentation/devicetree/bindings/i2c/i2c-aspeed.txt > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check' on your patch (DT_CHECKER_FLAGS is new in v5.13): yamllint warnings/errors: dtschema/dtc warnings/errors: Documentation/devicetree/bindings/i2c/aspeed,i2c.example.dt.yaml:0:0: /example-0/i2c-global-regs@0: failed to match any schema with compatible: ['aspeed,ast2600-i2c-global', 'syscon'] See https://patchwork.ozlabs.org/patch/1480769 This check can fail if there are any dependencies. The base for a patch series is generally the most recent rc1. If you already ran 'make dt_binding_check' and didn't see the above error(s), then make sure 'yamllint' is installed and dt-schema is up to date: pip3 install dtschema --upgrade Please check and re-submit.
On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > The register definition between AST2600 A2 and A3 is different. > This patch avoid new registers definition of AST2600 to use > this driver. We will submit the path for the new registers > definition of AST2600. The AST2600 v9 datasheet says that bit 2 selects between old and new register sets, and that the old register set is the default. Has the default changed for the A3?, and the datasheet is incorrect? Does the A3 still support the old register set? > > Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > --- > drivers/i2c/busses/i2c-aspeed.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c > index 724bf30600d6..007309077d9f 100644 > --- a/drivers/i2c/busses/i2c-aspeed.c > +++ b/drivers/i2c/busses/i2c-aspeed.c > @@ -19,14 +19,20 @@ > #include <linux/irqchip/chained_irq.h> > #include <linux/irqdomain.h> > #include <linux/kernel.h> > +#include <linux/mfd/syscon.h> > #include <linux/module.h> > #include <linux/of_address.h> > #include <linux/of_irq.h> > #include <linux/of_platform.h> > #include <linux/platform_device.h> > +#include <linux/regmap.h> > #include <linux/reset.h> > #include <linux/slab.h> > > +/* I2C Global Registers */ > +/* 0x0c : I2CG Global Control Register (AST2500) */ > +#define ASPEED_I2CG_GLOBAL_CTRL_REG 0x0c > + > /* I2C Register */ > #define ASPEED_I2C_FUN_CTRL_REG 0x00 > #define ASPEED_I2C_AC_TIMING_REG1 0x04 > @@ -973,6 +979,22 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) > struct resource *res; > int irq, ret; > > + if (of_device_is_compatible(pdev->dev.of_node, > + "aspeed,ast2600-i2c-bus")) { > + u32 global_ctrl; > + struct regmap *gr_regmap; > + > + gr_regmap = syscon_regmap_lookup_by_compatible("aspeed,ast2600-i2c-global"); > + > + if (IS_ERR(gr_regmap)) { > + ret = PTR_ERR(gr_regmap); > + } else { > + regmap_read(gr_regmap, ASPEED_I2CG_GLOBAL_CTRL_REG, &global_ctrl); > + if (global_ctrl & BIT(2)) > + return -EIO; > + } > + } > + > bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL); > if (!bus) > return -ENOMEM; > -- > 2.17.1 >
The 05/19/2021 15:29, Rob Herring wrote: > On Wed, 19 May 2021 16:04:29 +0800, Jamin Lin wrote: > > Add global-reg node for AST2600. Document the properties for > > "aspeed,ast2600-i2c-global" compatible node. > > > > Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > > --- > > .../devicetree/bindings/i2c/aspeed,i2c.yaml | 89 +++++++++++++++++++ > > .../devicetree/bindings/i2c/i2c-aspeed.txt | 49 ---------- > > 2 files changed, 89 insertions(+), 49 deletions(-) > > create mode 100644 Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > > delete mode 100644 Documentation/devicetree/bindings/i2c/i2c-aspeed.txt > > > > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check' > on your patch (DT_CHECKER_FLAGS is new in v5.13): > > yamllint warnings/errors: > > dtschema/dtc warnings/errors: > Documentation/devicetree/bindings/i2c/aspeed,i2c.example.dt.yaml:0:0: /example-0/i2c-global-regs@0: failed to match any schema with compatible: ['aspeed,ast2600-i2c-global', 'syscon'] > > See https://patchwork.ozlabs.org/patch/1480769 > > This check can fail if there are any dependencies. The base for a patch > series is generally the most recent rc1. > > If you already ran 'make dt_binding_check' and didn't see the above > error(s), then make sure 'yamllint' is installed and dt-schema is up to > date: > > pip3 install dtschema --upgrade > > Please check and re-submit. > Thanks for your review. yes, I did not add "DT_CHECKER_FLAGS" to check my patch. I will re-sent this patch. Thanks
The 05/19/2021 22:59, Joel Stanley wrote: > On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > The register definition between AST2600 A2 and A3 is different. > > This patch avoid new registers definition of AST2600 to use > > this driver. We will submit the path for the new registers > > definition of AST2600. > > The AST2600 v9 datasheet says that bit 2 selects between old and new > register sets, and that the old register set is the default. > > Has the default changed for the A3?, and the datasheet is incorrect? > > Does the A3 still support the old register set? > We suggest user to use the new i2c driver for AST2600 and we will sumbit it. This driver is used to AST2500 and AST2400 SOCs. Change this driver to check global register of i2c to avoid user build the wrong driver. > > > > Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > > --- > > drivers/i2c/busses/i2c-aspeed.c | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c > > index 724bf30600d6..007309077d9f 100644 > > --- a/drivers/i2c/busses/i2c-aspeed.c > > +++ b/drivers/i2c/busses/i2c-aspeed.c > > @@ -19,14 +19,20 @@ > > #include <linux/irqchip/chained_irq.h> > > #include <linux/irqdomain.h> > > #include <linux/kernel.h> > > +#include <linux/mfd/syscon.h> > > #include <linux/module.h> > > #include <linux/of_address.h> > > #include <linux/of_irq.h> > > #include <linux/of_platform.h> > > #include <linux/platform_device.h> > > +#include <linux/regmap.h> > > #include <linux/reset.h> > > #include <linux/slab.h> > > > > +/* I2C Global Registers */ > > +/* 0x0c : I2CG Global Control Register (AST2500) */ > > +#define ASPEED_I2CG_GLOBAL_CTRL_REG 0x0c > > + > > /* I2C Register */ > > #define ASPEED_I2C_FUN_CTRL_REG 0x00 > > #define ASPEED_I2C_AC_TIMING_REG1 0x04 > > @@ -973,6 +979,22 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) > > struct resource *res; > > int irq, ret; > > > > + if (of_device_is_compatible(pdev->dev.of_node, > > + "aspeed,ast2600-i2c-bus")) { > > + u32 global_ctrl; > > + struct regmap *gr_regmap; > > + > > + gr_regmap = syscon_regmap_lookup_by_compatible("aspeed,ast2600-i2c-global"); > > + > > + if (IS_ERR(gr_regmap)) { > > + ret = PTR_ERR(gr_regmap); > > + } else { > > + regmap_read(gr_regmap, ASPEED_I2CG_GLOBAL_CTRL_REG, &global_ctrl); > > + if (global_ctrl & BIT(2)) > > + return -EIO; > > + } > > + } > > + > > bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL); > > if (!bus) > > return -ENOMEM; > > -- > > 2.17.1 > >
Hi Jamin, On Thu, May 20, 2021 at 11:31:41AM +0800, Jamin Lin wrote: > The 05/19/2021 22:59, Joel Stanley wrote: > > On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > > > The register definition between AST2600 A2 and A3 is different. > > > This patch avoid new registers definition of AST2600 to use > > > this driver. We will submit the path for the new registers > > > definition of AST2600. > > > > The AST2600 v9 datasheet says that bit 2 selects between old and new > > register sets, and that the old register set is the default. > > > > Has the default changed for the A3?, and the datasheet is incorrect? > > > > Does the A3 still support the old register set? > > > We suggest user to use the new i2c driver for AST2600 and we will sumbit > it. This driver is used to AST2500 and AST2400 SOCs. Change this > driver to check global register of i2c to avoid user build the wrong driver. If I understand correctly, the answer implies old register set is still supported in A3 although aspeed suggest people using the new driver/mode? Can you please share more context behind the suggestion? Such as new register mode has better performance? Or some known issues that were deteted in old mode are fixed in new register mode? Cheers, Tao
The 05/21/2021 02:00, Tao Ren wrote: > Hi Jamin, > > On Thu, May 20, 2021 at 11:31:41AM +0800, Jamin Lin wrote: > > The 05/19/2021 22:59, Joel Stanley wrote: > > > On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > > > > > The register definition between AST2600 A2 and A3 is different. > > > > This patch avoid new registers definition of AST2600 to use > > > > this driver. We will submit the path for the new registers > > > > definition of AST2600. > > > > > > The AST2600 v9 datasheet says that bit 2 selects between old and new > > > register sets, and that the old register set is the default. > > > > > > Has the default changed for the A3?, and the datasheet is incorrect? > > > > > > Does the A3 still support the old register set? > > > > > We suggest user to use the new i2c driver for AST2600 and we will sumbit > > it. This driver is used to AST2500 and AST2400 SOCs. Change this > > driver to check global register of i2c to avoid user build the wrong driver. > > If I understand correctly, the answer implies old register set is still > supported in A3 although aspeed suggest people using the new driver/mode? > > Can you please share more context behind the suggestion? Such as new > register mode has better performance? Or some known issues that were > deteted in old mode are fixed in new register mode? > Yes, AST2600 A1, A2 and A3 support both old and new register set. The difference between old and new register set are the register address and supported registers. User can choose to use both old and new register set. However, ASPEED would like to change new register set by default for AST2600. Thanks-Jamin > > Cheers, > > Tao
The 05/19/2021 19:02, Zev Weiss wrote: > On Wed, May 19, 2021 at 03:04:27AM CDT, Jamin Lin wrote: > >The register definition between AST2600 A2 and A3 is different. > >This patch avoid new registers definition of AST2600 to use > >this driver. We will submit the path for the new registers > >definition of AST2600. > > > >Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > >--- > > drivers/i2c/busses/i2c-aspeed.c | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > >diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c > >index 724bf30600d6..007309077d9f 100644 > >--- a/drivers/i2c/busses/i2c-aspeed.c > >+++ b/drivers/i2c/busses/i2c-aspeed.c > >@@ -19,14 +19,20 @@ > > #include <linux/irqchip/chained_irq.h> > > #include <linux/irqdomain.h> > > #include <linux/kernel.h> > >+#include <linux/mfd/syscon.h> > > #include <linux/module.h> > > #include <linux/of_address.h> > > #include <linux/of_irq.h> > > #include <linux/of_platform.h> > > #include <linux/platform_device.h> > >+#include <linux/regmap.h> > > #include <linux/reset.h> > > #include <linux/slab.h> > > > >+/* I2C Global Registers */ > >+/* 0x0c : I2CG Global Control Register (AST2500) */ > >+#define ASPEED_I2CG_GLOBAL_CTRL_REG 0x0c > >+ > > /* I2C Register */ > > #define ASPEED_I2C_FUN_CTRL_REG 0x00 > > #define ASPEED_I2C_AC_TIMING_REG1 0x04 > >@@ -973,6 +979,22 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) > > struct resource *res; > > int irq, ret; > > > >+ if (of_device_is_compatible(pdev->dev.of_node, > >+ "aspeed,ast2600-i2c-bus")) { > >+ u32 global_ctrl; > >+ struct regmap *gr_regmap; > >+ > >+ gr_regmap = syscon_regmap_lookup_by_compatible("aspeed,ast2600-i2c-global"); > >+ > >+ if (IS_ERR(gr_regmap)) { > >+ ret = PTR_ERR(gr_regmap); > >+ } else { > >+ regmap_read(gr_regmap, ASPEED_I2CG_GLOBAL_CTRL_REG, &global_ctrl); > >+ if (global_ctrl & BIT(2)) > >+ return -EIO; > > A macro definition might be a bit nicer than a raw BIT(2) here I'd > think. Will modify > > Also, it seems a bit unfortunate to just bail on the device entirely if > we find this bit set (seems like a good way for a bootloader to > inadvertently DoS the kernel), though I guess poking global syscon bits > in the bus probe function might not be ideal. Could/should we consider > some module-level init code to ensure that bit is cleared? > > We use syscon API to get the global register of i2c not the specific i2c bus. Can you describe it more detail? Thanks-Jamin > Zev > > >+ } > >+ } > >+ > > bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL); > > if (!bus) > > return -ENOMEM; > >-- > >2.17.1 > >
On Mon, 24 May 2021 at 01:53, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > The 05/21/2021 02:00, Tao Ren wrote: > > Hi Jamin, > > > > On Thu, May 20, 2021 at 11:31:41AM +0800, Jamin Lin wrote: > > > The 05/19/2021 22:59, Joel Stanley wrote: > > > > On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > > > > > > > The register definition between AST2600 A2 and A3 is different. > > > > > This patch avoid new registers definition of AST2600 to use > > > > > this driver. We will submit the path for the new registers > > > > > definition of AST2600. > > > > > > > > The AST2600 v9 datasheet says that bit 2 selects between old and new > > > > register sets, and that the old register set is the default. > > > > > > > > Has the default changed for the A3?, and the datasheet is incorrect? > > > > > > > > Does the A3 still support the old register set? > > > > > > > We suggest user to use the new i2c driver for AST2600 and we will sumbit > > > it. This driver is used to AST2500 and AST2400 SOCs. Change this > > > driver to check global register of i2c to avoid user build the wrong driver. > > > > If I understand correctly, the answer implies old register set is still > > supported in A3 although aspeed suggest people using the new driver/mode? > > > > Can you please share more context behind the suggestion? Such as new > > register mode has better performance? Or some known issues that were > > deteted in old mode are fixed in new register mode? > > > Yes, AST2600 A1, A2 and A3 support both old and new register set. The difference > between old and new register set are the register address and supported registers. > User can choose to use both old and new register set. However, ASPEED would like to > change new register set by default for AST2600. We can certainly make the driver for the new register set the default for AST2600 when the new driver is merged. I disagree that we should introduce a run time check to fail to probe the old driver. Please do not merge this patch. Please focus your effort on getting the new driver merged instead. Cheers, Joel
On Sun, May 23, 2021 at 09:08:47PM CDT, Jamin Lin wrote: >The 05/19/2021 19:02, Zev Weiss wrote: >> On Wed, May 19, 2021 at 03:04:27AM CDT, Jamin Lin wrote: >> >The register definition between AST2600 A2 and A3 is different. >> >This patch avoid new registers definition of AST2600 to use >> >this driver. We will submit the path for the new registers >> >definition of AST2600. >> > >> >Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> >> >--- >> > drivers/i2c/busses/i2c-aspeed.c | 22 ++++++++++++++++++++++ >> > 1 file changed, 22 insertions(+) >> > >> >diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c >> >index 724bf30600d6..007309077d9f 100644 >> >--- a/drivers/i2c/busses/i2c-aspeed.c >> >+++ b/drivers/i2c/busses/i2c-aspeed.c >> >@@ -19,14 +19,20 @@ >> > #include <linux/irqchip/chained_irq.h> >> > #include <linux/irqdomain.h> >> > #include <linux/kernel.h> >> >+#include <linux/mfd/syscon.h> >> > #include <linux/module.h> >> > #include <linux/of_address.h> >> > #include <linux/of_irq.h> >> > #include <linux/of_platform.h> >> > #include <linux/platform_device.h> >> >+#include <linux/regmap.h> >> > #include <linux/reset.h> >> > #include <linux/slab.h> >> > >> >+/* I2C Global Registers */ >> >+/* 0x0c : I2CG Global Control Register (AST2500) */ >> >+#define ASPEED_I2CG_GLOBAL_CTRL_REG 0x0c >> >+ >> > /* I2C Register */ >> > #define ASPEED_I2C_FUN_CTRL_REG 0x00 >> > #define ASPEED_I2C_AC_TIMING_REG1 0x04 >> >@@ -973,6 +979,22 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) >> > struct resource *res; >> > int irq, ret; >> > >> >+ if (of_device_is_compatible(pdev->dev.of_node, >> >+ "aspeed,ast2600-i2c-bus")) { >> >+ u32 global_ctrl; >> >+ struct regmap *gr_regmap; >> >+ >> >+ gr_regmap = syscon_regmap_lookup_by_compatible("aspeed,ast2600-i2c-global"); >> >+ >> >+ if (IS_ERR(gr_regmap)) { >> >+ ret = PTR_ERR(gr_regmap); >> >+ } else { >> >+ regmap_read(gr_regmap, ASPEED_I2CG_GLOBAL_CTRL_REG, &global_ctrl); >> >+ if (global_ctrl & BIT(2)) >> >+ return -EIO; >> >> A macro definition might be a bit nicer than a raw BIT(2) here I'd >> think. >Will modify >> >> Also, it seems a bit unfortunate to just bail on the device entirely if >> we find this bit set (seems like a good way for a bootloader to >> inadvertently DoS the kernel), though I guess poking global syscon bits >> in the bus probe function might not be ideal. Could/should we consider >> some module-level init code to ensure that bit is cleared? >> >> >We use syscon API to get the global register of i2c not the specific i2c >bus. >Can you describe it more detail? Sure -- I just meant that if for whatever reason the kernel is booting on a system that's had that syscon bit set to enable the new register access mode (e.g. by a newer bootloader or something), it seems like we'd just give up entirely on enabling any i2c busses, when as far as I know there shouldn't be anything stopping us from resetting the bit back to be in the state this driver needs it to be in (old register mode) and then continuing along normally. Zev
The 05/24/2021 02:34, Joel Stanley wrote: > On Mon, 24 May 2021 at 01:53, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > The 05/21/2021 02:00, Tao Ren wrote: > > > Hi Jamin, > > > > > > On Thu, May 20, 2021 at 11:31:41AM +0800, Jamin Lin wrote: > > > > The 05/19/2021 22:59, Joel Stanley wrote: > > > > > On Wed, 19 May 2021 at 08:05, Jamin Lin <jamin_lin@aspeedtech.com> wrote: > > > > > > > > > > > > The register definition between AST2600 A2 and A3 is different. > > > > > > This patch avoid new registers definition of AST2600 to use > > > > > > this driver. We will submit the path for the new registers > > > > > > definition of AST2600. > > > > > > > > > > The AST2600 v9 datasheet says that bit 2 selects between old and new > > > > > register sets, and that the old register set is the default. > > > > > > > > > > Has the default changed for the A3?, and the datasheet is incorrect? > > > > > > > > > > Does the A3 still support the old register set? > > > > > > > > > We suggest user to use the new i2c driver for AST2600 and we will sumbit > > > > it. This driver is used to AST2500 and AST2400 SOCs. Change this > > > > driver to check global register of i2c to avoid user build the wrong driver. > > > > > > If I understand correctly, the answer implies old register set is still > > > supported in A3 although aspeed suggest people using the new driver/mode? > > > > > > Can you please share more context behind the suggestion? Such as new > > > register mode has better performance? Or some known issues that were > > > deteted in old mode are fixed in new register mode? > > > > > Yes, AST2600 A1, A2 and A3 support both old and new register set. The difference > > between old and new register set are the register address and supported registers. > > User can choose to use both old and new register set. However, ASPEED would like to > > change new register set by default for AST2600. > > We can certainly make the driver for the new register set the default > for AST2600 when the new driver is merged. > > I disagree that we should introduce a run time check to fail to probe > the old driver. Please do not merge this patch. > > Please focus your effort on getting the new driver merged instead. > > Cheers, > > Joel Thanks for your suggestion. I will submit the new i2c driver for AST2600 soon. Jamin
The 05/24/2021 21:16, Zev Weiss wrote: > On Sun, May 23, 2021 at 09:08:47PM CDT, Jamin Lin wrote: > >The 05/19/2021 19:02, Zev Weiss wrote: > >> On Wed, May 19, 2021 at 03:04:27AM CDT, Jamin Lin wrote: > >> >The register definition between AST2600 A2 and A3 is different. > >> >This patch avoid new registers definition of AST2600 to use > >> >this driver. We will submit the path for the new registers > >> >definition of AST2600. > >> > > >> >Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> > >> >--- > >> > drivers/i2c/busses/i2c-aspeed.c | 22 ++++++++++++++++++++++ > >> > 1 file changed, 22 insertions(+) > >> > > >> >diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c > >> >index 724bf30600d6..007309077d9f 100644 > >> >--- a/drivers/i2c/busses/i2c-aspeed.c > >> >+++ b/drivers/i2c/busses/i2c-aspeed.c > >> >@@ -19,14 +19,20 @@ > >> > #include <linux/irqchip/chained_irq.h> > >> > #include <linux/irqdomain.h> > >> > #include <linux/kernel.h> > >> >+#include <linux/mfd/syscon.h> > >> > #include <linux/module.h> > >> > #include <linux/of_address.h> > >> > #include <linux/of_irq.h> > >> > #include <linux/of_platform.h> > >> > #include <linux/platform_device.h> > >> >+#include <linux/regmap.h> > >> > #include <linux/reset.h> > >> > #include <linux/slab.h> > >> > > >> >+/* I2C Global Registers */ > >> >+/* 0x0c : I2CG Global Control Register (AST2500) */ > >> >+#define ASPEED_I2CG_GLOBAL_CTRL_REG 0x0c > >> >+ > >> > /* I2C Register */ > >> > #define ASPEED_I2C_FUN_CTRL_REG 0x00 > >> > #define ASPEED_I2C_AC_TIMING_REG1 0x04 > >> >@@ -973,6 +979,22 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) > >> > struct resource *res; > >> > int irq, ret; > >> > > >> >+ if (of_device_is_compatible(pdev->dev.of_node, > >> >+ "aspeed,ast2600-i2c-bus")) { > >> >+ u32 global_ctrl; > >> >+ struct regmap *gr_regmap; > >> >+ > >> >+ gr_regmap = syscon_regmap_lookup_by_compatible("aspeed,ast2600-i2c-global"); > >> >+ > >> >+ if (IS_ERR(gr_regmap)) { > >> >+ ret = PTR_ERR(gr_regmap); > >> >+ } else { > >> >+ regmap_read(gr_regmap, ASPEED_I2CG_GLOBAL_CTRL_REG, &global_ctrl); > >> >+ if (global_ctrl & BIT(2)) > >> >+ return -EIO; > >> > >> A macro definition might be a bit nicer than a raw BIT(2) here I'd > >> think. > >Will modify > >> > >> Also, it seems a bit unfortunate to just bail on the device entirely if > >> we find this bit set (seems like a good way for a bootloader to > >> inadvertently DoS the kernel), though I guess poking global syscon bits > >> in the bus probe function might not be ideal. Could/should we consider > >> some module-level init code to ensure that bit is cleared? > >> > >> > >We use syscon API to get the global register of i2c not the specific i2c > >bus. > >Can you describe it more detail? > > Sure -- I just meant that if for whatever reason the kernel is booting > on a system that's had that syscon bit set to enable the new register > access mode (e.g. by a newer bootloader or something), it seems like > we'd just give up entirely on enabling any i2c busses, when as far as I > know there shouldn't be anything stopping us from resetting the bit back > to be in the state this driver needs it to be in (old register mode) and > then continuing along normally. > > > Zev Thanks for your suggestion. I will submit the new i2c driver for AST2600. Jamin