Thanks Ryan. Can you shed some light on the meaning of the high-speed bit as well please ? About ASPEED_I2CD_M_HIGH_SPEED_EN, it is support for I2C specification "High speed transfer". And also device need support it. If you just speed up the I2C bus clock, you don’t have to enable ASPEED_I2CD_M_HIGH_SPEED_EN, just change the clock is ok. -----Original Message----- From: Benjamin Herrenschmidt [mailto:benh@xxxxxxxxxxxxxxxxxxx] Sent: Tuesday, April 25, 2017 5:35 PM To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>; Brendan Higgins <brendanhiggins@xxxxxxxxxx> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Mark Rutland <mark.rutland@xxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Jason Cooper <jason@xxxxxxxxxxxxxx>; Marc Zyngier <marc.zyngier@xxxxxxx>; Joel Stanley <joel@xxxxxxxxx>; Vladimir Zapolskiy <vz@xxxxxxxxx>; Kachalov Anton <mouse@xxxxxxx>; Cédric Le Goater <clg@xxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; OpenBMC Maillist <openbmc@xxxxxxxxxxxxxxxx> Subject: Re: [PATCH v6 4/5] i2c: aspeed: added driver for Aspeed I2C On Tue, 2017-04-25 at 08:50 +0000, Ryan Chen wrote: > Hello All, > ASPEED_I2CD_M_SDA_DRIVE_1T_EN, > ASPEED_I2CD_SDA_DRIVE_1T_EN is specific for some case usage. > For example, if i2c bus is use on "high speed" and "single slave and > master" and i2c bus is too long. It need drive SDA or SCL less lunacy. > It would enable it. > Otherwise, don’t enable it. especially in multi-master. > It can’t be enable. That smells like a specific enough use case that we should probably cover with a device-tree property, something like an empty "sda-extra-drive" property (empty properties are typically used for booleans, their presence means "true"). Thanks Ryan. Can you shed some light on the meaning of the high-speed bit as well please ? Does it force to a specific speed (ignoring the divisor) or we can still play with the clock high/low counts ? Cheers, Ben. > > > > Best Regards, > Ryan > > 信驊科技股份有限公司 > ASPEED Technology Inc. > 2F,No.15,Industry East Road 4.,Hsinchu Science Park, Hsinchu City > 30077, Taiwan > Tel: 886-3-578-9568 #857 > Fax: 886-3-578-9586 > ************* Email Confidentiality Notice ******************** > DISCLAIMER: > This message (and any attachments) may contain legally privileged > and/or other confidential information. If you have received it in > error, please notify the sender by reply e-mail and immediately delete > the e-mail and any attachments without copying or disclosing the > contents. Thank you. > > > -----Original Message----- > From: Brendan Higgins [mailto:brendanhiggins@xxxxxxxxxx] > Sent: Tuesday, April 25, 2017 4:32 PM > To: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx > >; Mark Rutland <mark.rutland@xxxxxxx>; Thomas Gleixner <tglx@linutro > nix.de>; Jason Cooper <jason@xxxxxxxxxxxxxx>; Marc Zyngier <marc.zyng > ier@xxxxxxx>; Joel Stanley <joel@xxxxxxxxx>; Vladimir Zapolskiy <vz@m > leia.com>; Kachalov Anton <mouse@xxxxxxx>; Cédric Le Goater <clg@kaod > .org>; linux-i2c@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; Linux > Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; OpenBMC Maillist > <openbmc@xxxxxxxxxxxxxxxx>; Ryan Chen <ryan_chen@xxxxxxxxxxxxxx> > Subject: Re: [PATCH v6 4/5] i2c: aspeed: added driver for Aspeed I2C > > Adding Ryan. > > On Mon, Apr 24, 2017 at 7:19 PM, Benjamin Herrenschmidt <benh@kernel. > crashing.org> wrote: > > On Mon, 2017-04-24 at 11:56 -0700, Brendan Higgins wrote: > > > > > +struct aspeed_i2c_bus { > > > > > + struct i2c_adapter adap; > > > > > + struct device *dev; > > > > > + void __iomem *base; > > > > > + /* Synchronizes I/O mem access to base. */ > > > > > + spinlock_t lock; > > > > > > > > I am not entirely convinced we need that lock. The i2c core will > > > > take a mutex protecting all operations on the bus. So we only > > > > need to synchronize between our "xfer" code and our interrupt > > > > handler. > > > > > > You are right if both having slave and master active at the same > > > time was not possible; however, it is. > > > > Right, I somewhat forgot about the slave case. > > > > ... > > > > > > Some of those error states probably also warrant a reset of the > > > > controller, I think aspeed does that in the SDK. > > > > > > For timeout and cmd_err, I do not see any argument against it; it > > > sounds like we are in a very messed up, very unknown state, so > > > full reset is probably the best last resort. > > > > Yup. > > > > > For SDA staying pulled down, I > > > think we can say with reasonable confidence that some device on > > > our bus is behaving very badly and I am not convinced that > > > resetting the controller is likely to do anything to help; > > > > Right. Hammering with STOPs and pray ... > > I think sending recovery mode sends stops as a part of the recovery > algorithm it executes. > > > > > > that being said, I really > > > do not have any good ideas to address that. So maybe praying and > > > resetting the controller is *the most reasonable thing to do.* I > > > would like to know what you think we should do in that case. > > > > Well, there's a (small ?) chance that it's a controller bug > > asserting the line so ... but there's little we can do if not. > > True. > > > > > > While I was thinking about this I also realized that the SDA line > > > check after recovery happens in the else branch, but SCL line > > > check does not happen after we attempt to STOP if SCL is hung. If > > > we decide to make special note SDA being hung by a device that > > > won't let go, we might want to make a special note that SCL is > > > hung by a device that won't let go. Just a thought. > > > > Maybe. Or just "unrecoverable error"... hopefully these don't happen > > too often ... We had cases of a TPM misbehaving like that. > > Yeah, definitely should print something out. > > > > > > > > +out: > > > > > > ... > > > > What about I2C_M_NOSTART ? > > > > > > > > Not that I've ever seen it used... ;-) > > > > > > Right now I am not doing any of the protocol mangling options, but > > > I can add them in if you think it is important for initial > > > support. > > > > No, not important, we can add that later if it ever becomes useful. > > > > ... > > > > > > In general, you always ACK all interrupts first. Then you handle > > > > the bits you have harvested. > > > > > > > > > > The documentation says to ACK the interrupt after handling in the > > > RX > > > case: > > > > > > <<< > > > S/W needs to clear this status bit to allow next data receiving. > > > > > > > > > > > > I will double check with Ryan to make sure TX works the same way. > > > > > > > > + if (irq_status & ASPEED_I2CD_INTR_ERROR || > > > > > + (!bus->msgs && bus->master_state != > > > > > ASPEED_I2C_MASTER_STOP)) { > > > > > > ... > > > > > > > > I would set master_state to "RECOVERY" (new state ?) and ensure > > > > those things are caught if they happen outside of a recovery. > > > > I replied privately ... as long as we ack before we start a new > > command we should be ok but we shouldn't ack after. > > > > Your latest patch still does that. It will do things like start a > > STOP command *then* ack the status bits. I'm pretty sure that's > > bogus. > > > > That way it's a lot simpler to simply move the > > > > writel(irq_status, bus->base + ASPEED_I2C_INTR_STS_REG); > > > > To either right after the readl of the status reg at the beginning > > of aspeed_i2c_master_irq(). > > > > I would be very surprised if that didn't work properly and wasn't > > much safer than what you are currently doing. > > I think I tried your way and it worked. In anycase, Ryan will be able > to clarify for us. > > > > > > Let me know if you still think we need a "RECOVERY" state. > > > > The way you just switch to stop state and store the error for later > > should work I think. > > > > > > > > > > > + if (bus->master_state == ASPEED_I2C_MASTER_START) { > > > > > > ... > > > > > > > > > + dev_dbg(bus->dev, > > > > > + "no slave present at %02x", > > > > > msg- > > > > > > addr); > > > > > > > > > > + status_ack |= ASPEED_I2CD_INTR_TX_NAK; > > > > > + bus->cmd_err = -EIO; > > > > > + do_stop(bus); > > > > > + goto out_no_complete; > > > > > + } else { > > > > > + status_ack |= ASPEED_I2CD_INTR_TX_ACK; > > > > > + if (msg->flags & I2C_M_RD) > > > > > + bus->master_state = > > > > > ASPEED_I2C_MASTER_RX; > > > > > + else > > > > > + bus->master_state = > > > > > ASPEED_I2C_MASTER_TX_FIRST; > > > > > > > > What about the SMBUS_QUICK case ? (0-len transfer). Do we need > > > > to handle this here ? A quick look at the TX_FIRST case makes me > > > > think we are ok there but I'm not sure about the RX case. > > > > > > I did not think that there is an SMBUS_QUICK RX. Could you point > > > me to an example? > > > > Not so much an RX, it's more like you are sending a 1-bit data in > > the place of the Rd/Wr bit. So you have a read with a lenght of 0, I > > don't think in that case you should set ASPEED_I2CD_M_RX_CMD in > > __aspeed_i2c_do_start > > Forget what I said, I was just not thinking about the fact that SMBus > emulation causes the data bit to be encoded as the R/W flag. I see > what you are saying; you are correct. > > > > > > > I'm not sure the RX case is tight also. What completion does the > > > > HW give you for the address cycle ? Won't you get that before it > > > > has received the first character ? IE. You fall through to the > > > > read case of the state machine with the read potentially not > > > > complete yet no ? > > > > > > ... > > > > > + case ASPEED_I2C_MASTER_RX: > > > > > + if (!(irq_status & ASPEED_I2CD_INTR_RX_DONE)) { > > > > > + dev_err(bus->dev, "master failed to > > > > > RX"); > > > > > + goto out_complete; > > > > > + } > > > > > > > > See my comment above for a bog standard i2c_read. Aren't you > > > > getting the completion for the address before the read is even > > > > started ? > > > > > > In practice no, but it is probably best to be safe :-) > > > > Yup :) > > > > > > > > > + status_ack |= ASPEED_I2CD_INTR_RX_DONE; > > > > > + > > > > > + recv_byte = aspeed_i2c_read(bus, > > > > > ASPEED_I2C_BYTE_BUF_REG) >> 8; > > > > > + msg->buf[bus->buf_index++] = recv_byte; > > > > > + > > > > > + if (msg->flags & I2C_M_RECV_LEN && > > > > > + recv_byte <= I2C_SMBUS_BLOCK_MAX) { > > > > > + msg->len = recv_byte + > > > > > + ((msg->flags & > > > > > I2C_CLIENT_PEC) ? 2 : 1); > > > > > > ... > > > > > + return ((clk_high << ASPEED_I2CD_TIME_SCL_HIGH_SHIFT) > > > > > + & ASPEED_I2CD_TIME_SCL_HIGH_MASK) > > > > > + | ((clk_low << > > > > > ASPEED_I2CD_TIME_SCL_LOW_SHIFT) > > > > > + & ASPEED_I2CD_TIME_SCL_LOW_MASK) > > > > > + | (base_clk & > > > > > ASPEED_I2CD_TIME_BASE_DIVISOR_MASK); > > > > > +} > > > > > > > > As I think I mentioned earlier, the AST2500 has a slightly > > > > different register layout which support larger values for high > > > > and low, thus allowing a finer granularity. > > > > > > I am developing against the 2500. > > > > Yes but we'd like the driver to work with both :-) > > Right, I thought you were making an assertion about the 2500, if you > are making an assertion about the 2400, I do not know and do not have > one handy. > > > > > > > BTW. In case you haven't, I would suggest you copy/paste the > > > > above in a userspace app and run it for all frequency divisors > > > > and see if your results match the aspeed table :) > > > > > > Good call. > > > > If you end up doing that, can you shoot it my way ? I can take care > > of making sure it's all good for the 2400. > > Will do. > > > > > > > > +static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus, > > > > > + struct platform_device *pdev) { > > > > > + u32 clk_freq, divisor; > > > > > + struct clk *pclk; > > > > > + int ret; > > > > > + > > > > > + pclk = devm_clk_get(&pdev->dev, NULL); > > > > > + if (IS_ERR(pclk)) { > > > > > + dev_err(&pdev->dev, "clk_get failed\n"); > > > > > + return PTR_ERR(pclk); > > > > > + } > > > > > + ret = of_property_read_u32(pdev->dev.of_node, > > > > > + "clock-frequency", > > > > > &clk_freq); > > > > > > > > See my previous comment about calling that 'bus-frequency' > > > > rather > > > > than 'clock-frequency'. > > > > > > > > > + if (ret < 0) { > > > > > + dev_err(&pdev->dev, > > > > > + "Could not read clock-frequency > > > > > property\n"); > > > > > + clk_freq = 100000; > > > > > + } > > > > > + divisor = clk_get_rate(pclk) / clk_freq; > > > > > + /* We just need the clock rate, we don't actually use > > > > > the > > > > > clk object. */ > > > > > + devm_clk_put(&pdev->dev, pclk); > > > > > + > > > > > + /* Set AC Timing */ > > > > > + if (clk_freq / 1000 > 1000) { > > > > > + aspeed_i2c_write(bus, aspeed_i2c_read(bus, > > > > > + ASPEED_I2 > > > > > C_FU > > > > > N_CTRL_REG) | > > > > > + ASPEED_I2CD_M_HIGH_SPEED_EN | > > > > > + ASPEED_I2CD_M_SDA_DRIVE_1T_EN | > > > > > + ASPEED_I2CD_SDA_DRIVE_1T_EN, > > > > > + ASPEED_I2C_FUN_CTRL_REG); > > > > > + > > > > > + aspeed_i2c_write(bus, 0x3, > > > > > ASPEED_I2C_AC_TIMING_REG2); > > > > > + aspeed_i2c_write(bus, > > > > > aspeed_i2c_get_clk_reg_val(divisor), > > > > > + ASPEED_I2C_AC_TIMING_REG1); > > > > > > > > I already discussed by doubts about the above. I can try to > > > > scope it with the EVB if you don't get to it. For now I'd rather > > > > take the code out. > > > > > > > > We should ask aspeed from what frequency the "1T" stuff is > > > > useful. > > > > > > Will do, I will try to rope Ryan in on the next review; it will be > > > good for him to get used to working with upstream anyway. > > > > Yup. However, for the sake of getting something upstream (and in > > OpenBMC 4.10 kernel) asap, I would suggest just dropping support for > > those fast speeds for now, we can add them back later. > > Alright, that's fine. Still, Ryan, could you provide some context on > this? > > > > > > > > > > > > + } else { > > > > > + aspeed_i2c_write(bus, > > > > > aspeed_i2c_get_clk_reg_val(divisor), > > > > > + ASPEED_I2C_AC_TIMING_REG1); > > > > > + aspeed_i2c_write(bus, ASPEED_NO_TIMEOUT_CTRL, > > > > > + ASPEED_I2C_AC_TIMING_REG2); > > > > > + } > > > > > > ... > > > > > + spin_lock_init(&bus->lock); > > > > > + init_completion(&bus->cmd_complete); > > > > > + bus->adap.owner = THIS_MODULE; > > > > > + bus->adap.retries = 0; > > > > > + bus->adap.timeout = 5 * HZ; > > > > > + bus->adap.algo = &aspeed_i2c_algo; > > > > > + bus->adap.algo_data = bus; > > > > > + bus->adap.dev.parent = &pdev->dev; > > > > > + bus->adap.dev.of_node = pdev->dev.of_node; > > > > > + snprintf(bus->adap.name, sizeof(bus->adap.name), > > > > > "Aspeed > > > > > i2c"); > > > > > > > > Another trivial one, should we put some kind of bus number in > > > > that string ? > > > > > > Whoops, looks like I missed this one; I will get to it in the next > > > revision. > > > > Ok. I noticed you missed that in v7, so I assume you mean v8 :-) > > Yep, I will get it in v8. > > > > > > > > > > > > + bus->dev = &pdev->dev; > > > > > + > > > > > + /* reset device: disable master & slave functions */ > > > > > + aspeed_i2c_write(bus, 0, ASPEED_I2C_FUN_CTRL_REG); > > > > > > ... > > > -- > > > To unsubscribe from this list: send the line "unsubscribe > > > devicetree" > > > in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo > > > info at http://vger.kernel.org/majordomo-info.html ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
