| Message ID | 1369812944-685-2-git-send-email-oleksandr.dmytryshyn@ti.com |
|---|---|
| State | Superseded |
| Headers | show |
Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: > Starting from the OMAP chips with version2 registers scheme there are > 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage > interrupts instead of the older OMAP chips with old scheme which have > only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET > register for enabling interrupts and I2C_IRQENABLE_CLR register for > disabling interrupts. Why? (changelogs should always answer the "why" question) IOW, what is broken without this change, how does it fail? And equally important, how is it currently working? Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/29/2013 08:22 PM, Kevin Hilman wrote: > Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: > >> Starting from the OMAP chips with version2 registers scheme there are >> 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage >> interrupts instead of the older OMAP chips with old scheme which have >> only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET >> register for enabling interrupts and I2C_IRQENABLE_CLR register for >> disabling interrupts. > Why? (changelogs should always answer the "why" question) > > IOW, what is broken without this change, how does it fail? And equally > important, how is it currently working? > > Kevin > > Hi, Kevin. If the i2c controller during suspend will generate an interrupt, it can lead to unpredictable behaviour in the kernel. Based on the logic of the kernel code interrupts from i2c should be prohibited during suspend. Kernel writes 0 to the I2C_IE register in the omap_i2c_runtime_suspend() function. In the other side kernel writes saved interrupt flags to the I2C_IE register in omap_i2c_runtime_resume() function. I.e. interrupts should be disabled during suspend. This works for chips with version1 registers scheme. Interrupts are disabled during suspend. For chips with version2 scheme registers writting 0 to the I2C_IE register does nothing (because now the I2C_IRQENABLE_SET register is located at this address ). This register is used to enable interrupts. For disabling interrupts I2C_IRQENABLE_CLR register should be used. I've checked that interrupts in the i2c controller are still enabled after writting 0 to the I2C_IE register. But with my patch interrupts are disabled in the omap_i2c_runtime_suspend() function.
Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: > On 05/29/2013 08:22 PM, Kevin Hilman wrote: >> Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: >> >>> Starting from the OMAP chips with version2 registers scheme there are >>> 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage >>> interrupts instead of the older OMAP chips with old scheme which have >>> only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET >>> register for enabling interrupts and I2C_IRQENABLE_CLR register for >>> disabling interrupts. >> Why? (changelogs should always answer the "why" question) >> >> IOW, what is broken without this change, how does it fail? And equally >> important, how is it currently working? >> >> Kevin >> >> > Hi, Kevin. > > If the i2c controller during suspend will generate an interrupt, it > can lead to unpredictable behaviour in the kernel. > > Based on the logic of the kernel code interrupts from i2c should be > prohibited during suspend. Kernel writes 0 to the I2C_IE register in > the omap_i2c_runtime_suspend() function. In the other side kernel > writes saved interrupt flags to the I2C_IE register in > omap_i2c_runtime_resume() function. I.e. interrupts should be disabled > during suspend. > > This works for chips with version1 registers scheme. Interrupts are > disabled during suspend. For chips with version2 scheme registers > writting 0 to the I2C_IE register does nothing (because now the > I2C_IRQENABLE_SET register is located at this address ). This register > is used to enable interrupts. For disabling interrupts > I2C_IRQENABLE_CLR register should be used. > > I've checked that interrupts in the i2c controller are still enabled > after writting 0 to the I2C_IE register. But with my patch interrupts > are disabled in the omap_i2c_runtime_suspend() function. Yes, I understand why your patch works, and it looks correct to me. My main concern is that the changelog is missing a detailed description of the problem that is being solved, as well as a summary of why this has ever worked. I guess we've just been lucky and not seen interrupts during suspend? Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/30/2013 05:18 PM, Kevin Hilman wrote: > Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: > >> On 05/29/2013 08:22 PM, Kevin Hilman wrote: >>> Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> writes: >>> >>>> Starting from the OMAP chips with version2 registers scheme there are >>>> 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage >>>> interrupts instead of the older OMAP chips with old scheme which have >>>> only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET >>>> register for enabling interrupts and I2C_IRQENABLE_CLR register for >>>> disabling interrupts. >>> Why? (changelogs should always answer the "why" question) >>> >>> IOW, what is broken without this change, how does it fail? And equally >>> important, how is it currently working? >>> >>> Kevin >>> >>> >> Hi, Kevin. >> >> If the i2c controller during suspend will generate an interrupt, it >> can lead to unpredictable behaviour in the kernel. >> >> Based on the logic of the kernel code interrupts from i2c should be >> prohibited during suspend. Kernel writes 0 to the I2C_IE register in >> the omap_i2c_runtime_suspend() function. In the other side kernel >> writes saved interrupt flags to the I2C_IE register in >> omap_i2c_runtime_resume() function. I.e. interrupts should be disabled >> during suspend. >> >> This works for chips with version1 registers scheme. Interrupts are >> disabled during suspend. For chips with version2 scheme registers >> writting 0 to the I2C_IE register does nothing (because now the >> I2C_IRQENABLE_SET register is located at this address ). This register >> is used to enable interrupts. For disabling interrupts >> I2C_IRQENABLE_CLR register should be used. >> >> I've checked that interrupts in the i2c controller are still enabled >> after writting 0 to the I2C_IE register. But with my patch interrupts >> are disabled in the omap_i2c_runtime_suspend() function. > Yes, I understand why your patch works, and it looks correct to me. > > My main concern is that the changelog is missing a detailed description > of the problem that is being solved, as well as a summary of why this > has ever worked. I guess we've just been lucky and not seen interrupts > during suspend? > > Kevin Hi, Kevin. Yes. You are right about the interrupts.
diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index e02f9e3..2419899 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -180,6 +180,8 @@ enum { #define I2C_OMAP_ERRATA_I207 (1 << 0) #define I2C_OMAP_ERRATA_I462 (1 << 1) +#define OMAP_I2C_INTERRUPTS_MASK 0x6FFF + struct omap_i2c_dev { spinlock_t lock; /* IRQ synchronization */ struct device *dev; @@ -193,6 +195,7 @@ struct omap_i2c_dev { long latency); u32 speed; /* Speed of bus in kHz */ u32 flags; + u16 scheme; u16 cmd_err; u8 *buf; u8 *regs; @@ -1082,7 +1085,7 @@ omap_i2c_probe(struct platform_device *pdev) int irq; int r; u32 rev; - u16 minor, major, scheme; + u16 minor, major; /* NOTE: driver uses the static register mapping */ mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); @@ -1159,8 +1162,8 @@ omap_i2c_probe(struct platform_device *pdev) */ rev = __raw_readw(dev->base + 0x04); - scheme = OMAP_I2C_SCHEME(rev); - switch (scheme) { + dev->scheme = OMAP_I2C_SCHEME(rev); + switch (dev->scheme) { case OMAP_I2C_SCHEME_0: dev->regs = (u8 *)reg_map_ip_v1; dev->rev = omap_i2c_read_reg(dev, OMAP_I2C_REV_REG); @@ -1289,7 +1292,11 @@ static int omap_i2c_runtime_suspend(struct device *dev) _dev->iestate = omap_i2c_read_reg(_dev, OMAP_I2C_IE_REG); - omap_i2c_write_reg(_dev, OMAP_I2C_IE_REG, 0); + if (_dev->scheme == OMAP_I2C_SCHEME_0) + omap_i2c_write_reg(_dev, OMAP_I2C_IE_REG, 0); + else + omap_i2c_write_reg(_dev, OMAP_I2C_IP_V2_IRQENABLE_CLR, + OMAP_I2C_INTERRUPTS_MASK); if (_dev->rev < OMAP_I2C_OMAP1_REV_2) { omap_i2c_read_reg(_dev, OMAP_I2C_IV_REG); /* Read clears */
Starting from the OMAP chips with version2 registers scheme there are 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage interrupts instead of the older OMAP chips with old scheme which have only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET register for enabling interrupts and I2C_IRQENABLE_CLR register for disabling interrupts. Because the registers I2C_IRQENABLE_SET and I2C_IE have the same addresses, the interrupt enabling procedure is unchanged. Change-Id: Ie49165990a4e7c67a4ccf2e4a66cd3b78f2e2b70 Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> --- drivers/i2c/busses/i2c-omap.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)