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Date: Wed, 31 Mar 2021 19:23:08 +0530
From: "Goswami, Sanket" <Sanket.Goswami@....com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: jarkko.nikula@...ux.intel.com, mika.westerberg@...ux.intel.com,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
Shyam Sundar S K <Shyam-sundar.S-k@....com>,
Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>
Subject: Re: [PATCH v3] i2c: designware: Add driver support for AMD NAVI GPU
Hi Andy,
Thanks for the review.
On 30-Mar-21 15:21, Andy Shevchenko wrote:
> [CAUTION: External Email]
>
> On Tue, Mar 30, 2021 at 12:17:15PM +0530, Sanket Goswami wrote:
>
> Thanks for an update, my comments below.
>
>> The Latest AMD NAVI GPU card has an integrated Type-C controller and
>> Designware I2C with PCI Interface. The Type-C controller can be
>> accessed over I2C.
>
> Entire controller? You probably have to rephrase this to make sure
> that everybody understands what you are talking about (presumable it's
> "USB PD for Type-C" rather than "Type-C controller").
>
>> The client driver is part of the USB Type-C UCSI
>> driver.
>
>> Also, there exists a couple of notable IP limitations that are dealt as
>> workarounds:
>> - I2C transaction work on a polling mode as IP does not generate
>> interrupt.
>> - I2C read command sent twice to address the IP issues.
>> - AMD NAVI GPU based products are already in the commercial market,
>> hence some of the I2C parameters are statically programmed as it can
>> not be part of ACPI table.
>
> ...
>
>> + if (dev->flags & MODEL_AMD_NAVI_GPU)
>
> if ((dev->flags & MODEL_MASK) == MODEL_AMD_NAVI_GPU)
>
>> + map_cfg.max_register = AMD_UCSI_INTR_REG;
>
> ...
>
>> #define ACCESS_INTR_MASK BIT(0)
>> #define ACCESS_NO_IRQ_SUSPEND BIT(1)
>>
>> +#define MODEL_AMD_NAVI_GPU BIT(2)
>
> This bit number doesn't fit MODEL_MASK.
>
>> #define MODEL_MSCC_OCELOT BIT(8)
>> #define MODEL_BAIKAL_BT1 BIT(9)
>> #define MODEL_MASK GENMASK(11, 8)
>
> + blank line here.
>
>> +#define AMD_UCSI_INTR_EN 0xd
>> +#define AMD_UCSI_INTR_REG 0x474
>
> Not sure I understood where is what. 0xd is a value or register offset?
> Needs to be register offset first, followed by values. Also add a comment
> to explain what is this register for.
>
> ...
>
>> +#define AMD_TIMEOUT_MIN_MSEC 10000
>> +#define AMD_TIMEOUT_MAX_MSEC 11000
>
> MSEC -> MS
>
> So, it's 10 and 11 seconds?! Needs a very good comment about such a long
> delays.
>
> ...
>
>> +static int i2c_dw_check_stopbit(struct dw_i2c_dev *dev)
>> +{
>> + u32 val;
>> + int ret;
>> +
>> + ret = regmap_read_poll_timeout(dev->map, DW_IC_INTR_STAT, val,
>> + !(val & DW_IC_INTR_STOP_DET),
>> + 1100, 20000);
>> + if (ret) {
>> + dev_err(dev->dev, "i2c timeout error %d\n", ret);
>
>> + return -ETIMEDOUT;
>
> Why shadowed error code?
>
>> + }
>
>> + regmap_read(dev->map, DW_IC_CLR_INTR, &val);
>
> So, if above stops the polling, the condition is that bit is cleared.
> How this makes it set again? Elaborate, please, why do you need the below
> conditional and under which circumstances it may become true.
>
>> + if (val & DW_IC_INTR_STOP_DET)
>> + return -ETIMEDOUT;
>> +
>> + return 0;
>> +}
>> +
>> +static int i2c_dw_status(struct dw_i2c_dev *dev)
>> +{
>> + int status;
>> +
>> + status = i2c_dw_wait_bus_not_busy(dev);
>> + if (status)
>
>> + return -ETIMEDOUT;
>
> Why you always shadow error codes?
>
>> + return i2c_dw_check_stopbit(dev);
>> +}
>> +
>> +/*
>> + * Initiate and continue master read/write transaction with polling
>> + * based transfer routine afterward write messages into the tx buffer.
>
> tx -> Tx
>
>> + */
>> +static int amd_i2c_dw_xfer_quirk(struct i2c_adapter *adap, struct i2c_msg *msgs, int num_msgs)
>> +{
>> + struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
>> + int msg_wrt_idx, msg_itr_lmt, buf_len, data_idx;
>> + int cmd = 0, ret, status;
>> + u8 *tx_buf;
>> + u32 val;
>
> + blank line.
>
>> + /*
>> + * In order to enable the interrupt for UCSI i.e. AMD NAVI GPU card,
>> + * it is mandatory to set the right value in specific register
>> + * (offset:0x474) as per the hardware IP specification.
>> + */
>> + regmap_write(dev->map, AMD_UCSI_INTR_REG, AMD_UCSI_INTR_EN);
>
>> + ret = i2c_dw_acquire_lock(dev);
>
> Do you need this? Does AMD have that ugly ACPI based mutex?
>
>> + if (ret) {
>> + dev_err(dev->dev, "Failed to get bus ownership\n");
>> + return ret;
>> + }
>> +
>> + dev->msgs = msgs;
>> + dev->msgs_num = num_msgs;
>> + i2c_dw_xfer_init(dev);
>> + i2c_dw_disable_int(dev);
>> +
>> + /* Initiate messages read/write transaction */
>> + for (msg_wrt_idx = 0; msg_wrt_idx < num_msgs; msg_wrt_idx++) {
>> + tx_buf = msgs[msg_wrt_idx].buf;
>> + buf_len = msgs[msg_wrt_idx].len;
>> +
>> + if (!(msgs[msg_wrt_idx].flags & I2C_M_RD))
>> + regmap_write(dev->map, DW_IC_TX_TL, buf_len - 1);
>> + /*
>> + * Initiate the i2c read/write transaction of buffer length,
>> + * and poll for bus busy status. For the last message transfer,
>> + * update the command with stopbit enable.
>> + */
>> + for (msg_itr_lmt = buf_len; msg_itr_lmt > 0; msg_itr_lmt--) {
>> + if (msg_wrt_idx == num_msgs - 1 && msg_itr_lmt == 1)
>> + cmd |= BIT(9);
>> +
>> + if (msgs[msg_wrt_idx].flags & I2C_M_RD) {
>> + /* Due to hardware bug, need to write the same command twice. */
>> + regmap_write(dev->map, DW_IC_DATA_CMD, 0x100);
>> + regmap_write(dev->map, DW_IC_DATA_CMD, 0x100 | cmd);
>> + if (cmd) {
>> + regmap_write(dev->map, DW_IC_TX_TL, 2 * (buf_len - 1));
>> + regmap_write(dev->map, DW_IC_RX_TL, 2 * (buf_len - 1));
>> + /*
>> + * Need to check the stop bit. However, it cannot be
>> + * detected from the registers so we check it always
>> + * when read/write the last byte.
>> + */
>> + status = i2c_dw_status(dev);
>> + if (status) {
>
>> + ret = -ETIMEDOUT;
>
> ???
>
>> + goto lock_release;
>> + }
>> + for (data_idx = 0; data_idx < buf_len; data_idx++) {
>> + regmap_read(dev->map, DW_IC_DATA_CMD, &val);
>> + tx_buf[data_idx] = val;
>> + }
>> + status = i2c_dw_check_stopbit(dev);
>> + if (status) {
>
>> + ret = -ETIMEDOUT;
>
> ???
>
>> + goto lock_release;
>> + }
>> + }
>> + } else {
>> + regmap_write(dev->map, DW_IC_DATA_CMD, *tx_buf++ | cmd);
>> + usleep_range(AMD_TIMEOUT_MIN_MSEC, AMD_TIMEOUT_MAX_MSEC);
>> + }
>> + }
>> + status = i2c_dw_check_stopbit(dev);
>> + if (status) {
>
>> + ret = -ETIMEDOUT;
>
> ???
>
>> + goto lock_release;
>> + }
>> + }
>
>> +lock_release:
>> + i2c_dw_release_lock(dev);
>
> So you need this? Why?
>
>> + return ret;
>> +}
>
> ...
>
>> pm_runtime_get_sync(dev->dev);
>
> + Blank line.
>
>> + /*
>> + * Initiate I2C message transfer when AMD NAVI GPU card is enabled,
>> + * As it is polling based transfer mechanism, which does not support
>> + * interrupt based functionalities of existing DesignWare driver.
>> + */
>> + if (dev->flags & MODEL_AMD_NAVI_GPU) {
>> + ret = amd_i2c_dw_xfer_quirk(adap, msgs, num);
>> + goto done_nolock;
>> + }
>
> ...
>
>> +static int amd_i2c_adap_quirk(struct dw_i2c_dev *dev)
>> +{
>> + struct i2c_adapter *adap = &dev->adapter;
>> + int ret;
>> +
>> + pm_runtime_get_noresume(dev->dev);
>> + ret = i2c_add_numbered_adapter(adap);
>
>> + if (ret)
>> + dev_err(dev->dev, "Failed to add adapter : %d\n", ret);
>
> Why is this under PM hooks?
As driver supports PM runtime, PM runtime related hooks/calls are maintained
as per the existing driver implementation.
>
>> + pm_runtime_put_noidle(dev->dev);
>> +
>> + return ret;
>> +}
>
>> int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>> {
>> struct i2c_adapter *adap = &dev->adapter;
>> @@ -774,6 +922,9 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>> adap->dev.parent = dev->dev;
>> i2c_set_adapdata(adap, dev);
>>
>> + if (dev->flags & MODEL_AMD_NAVI_GPU)
>> + return amd_i2c_adap_quirk(dev);
>> +
>> if (dev->flags & ACCESS_NO_IRQ_SUSPEND) {
>> irq_flags = IRQF_NO_SUSPEND;
>> } else {
>
> ...
>
>> +#define AMD_CLK_RATE_HZ 100000
>
> Shouldn't others be also defined like this?
>
> ...
>
> Add a TODO line here to point out that nVidia driver and this should be
> deduplicated on how they instantiate a USB PD slave device.
>
>> +static int navi_amd_register_client(struct dw_i2c_dev *dev)
>> +{
>> + struct i2c_board_info info;
>> +
>> + memset(&info, 0, sizeof(struct i2c_board_info));
>> + strscpy(info.type, "ccgx-ucsi", I2C_NAME_SIZE);
>> + info.addr = 0x08;
>> + info.irq = dev->irq;
>> +
>> + dev->slave = i2c_new_client_device(&dev->adapter, &info);
>> + if (!dev->slave)
>> + return -ENODEV;
>> +
>> + return 0;
>> +}
>
> ...
>
>> + if (dev->flags & MODEL_AMD_NAVI_GPU)
>> + r = navi_amd_register_client(dev);
>
>> + if (r) {
>> + dev_err(dev->dev, "register client failed with %d\n", r);
>> + return r;
>> + }
>
> This seems to be on a wrong scope.
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Remaining review comments will be addressed as part of v4.
Thanks,
Sanket
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