Re: [PATCH 5/7] i2c: qcom-geni: Add support for GPI DMA

Vinod Koul
2021-01-12T05:51:25Z

On 11-01-21, 12:14, Bjorn Andersson wrote:
> On Mon 11 Jan 09:16 CST 2021, Vinod Koul wrote:
>
> > This adds capability to use GSI DMA for I2C transfers
> >
> > Signed-off-by: Vinod Koul <vkoul@kernel.org>
> > ---
> > drivers/i2c/busses/i2c-qcom-geni.c | 246 ++++++++++++++++++++++++++++-
> > 1 file changed, 244 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> > index 046d241183c5..6978480fb4d1 100644
> > --- a/drivers/i2c/busses/i2c-qcom-geni.c
> > +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> > @@ -12,7 +12,9 @@
> > #include <linux/of.h>
> > #include <linux/platform_device.h>
> > #include <linux/pm_runtime.h>
> > +#include <linux/dmaengine.h>
> > #include <linux/qcom-geni-se.h>
> > +#include <linux/dma/qcom-gpi-dma.h>
> > #include <linux/spinlock.h>
> >
> > #define SE_I2C_TX_TRANS_LEN 0x26c
> > @@ -48,6 +50,8 @@
> > #define LOW_COUNTER_SHFT 10
> > #define CYCLE_COUNTER_MSK GENMASK(9, 0)
> >
> > +#define I2C_PACK_EN (BIT(0) | BIT(1))
> > +
> > enum geni_i2c_err_code {
> > GP_IRQ0,
> > NACK,
> > @@ -72,6 +76,12 @@ enum geni_i2c_err_code {
> > #define XFER_TIMEOUT HZ
> > #define RST_TIMEOUT HZ
> >
> > +enum i2c_se_mode {
> > + UNINITIALIZED,
> > + FIFO_SE_DMA,
> > + GSI_ONLY,
> > +};
> > +
> > struct geni_i2c_dev {
> > struct geni_se se;
> > u32 tx_wm;
> > @@ -86,6 +96,17 @@ struct geni_i2c_dev {
> > u32 clk_freq_out;
> > const struct geni_i2c_clk_fld *clk_fld;
> > int suspended;
> > + struct dma_chan *tx_c;
> > + struct dma_chan *rx_c;
> > + dma_cookie_t rx_cookie, tx_cookie;
> > + dma_addr_t tx_ph;
> > + dma_addr_t rx_ph;
> > + int cfg_sent;
>
> bool?

ok

>
> > + struct dma_async_tx_descriptor *tx_desc;
> > + struct dma_async_tx_descriptor *rx_desc;
> > + enum i2c_se_mode se_mode;
>
> bool gsi_only;

I think fifo_mode would be more apt... since we check for other modes in
the code

>
> > + bool cmd_done;
>
> Unused?

heh, will remove..

> > + bool is_shared;
>
> Used but meaningless?

Will drop

>
> > };
> >
> > struct geni_i2c_err_log {
> > @@ -429,6 +450,183 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> > return gi2c->err;
> > }
> >
> > +static void i2c_gsi_cb_result(void *cb, const struct dmaengine_result *result)
> > +{
> > + struct geni_i2c_dev *gi2c = cb;
> > +
> > + if (result->result != DMA_TRANS_NOERROR) {
> > + dev_err(gi2c->se.dev, "DMA txn failed:%d\n", result->result);
> > + return;
> > + }
> > +
> > + if (result->residue)
> > + dev_dbg(gi2c->se.dev, "DMA xfer has pending: %d\n", result->residue);
> > +
> > + complete(&gi2c->done);
> > +}
> > +
> > +static int geni_i2c_gsi_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
> > + int num)
> > +{
> > + struct geni_i2c_dev *gi2c = i2c_get_adapdata(adap);
> > + struct dma_slave_config config;
> > + struct gpi_i2c_config peripheral;
> > + int i, ret = 0, timeout = 0;
> > +
> > + memset(&config, 0, sizeof(config));
>
> Assign {} to config during declaration.

ok

>
> > + memset(&peripheral, 0, sizeof(peripheral));
> > + config.peripheral_config = &peripheral;
> > + config.peripheral_size = sizeof(peripheral);
> > +
> > + if (!gi2c->tx_c) {
> > + gi2c->tx_c = dma_request_slave_channel(gi2c->se.dev, "tx");
>
> So object is reused for all future transfers as well?
> Seems reasonable, but it should be released on driver removal?
>
> Could it be requested at probe time instead?

yes it can be done, i would move it..

>
> > + if (!gi2c->tx_c) {
> > + dev_err(gi2c->se.dev, "tx dma_request_slave_channel fail\n");
> > + ret = -EIO;
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > + }
> > +
> > + if (!gi2c->rx_c) {
> > + gi2c->rx_c = dma_request_slave_channel(gi2c->se.dev, "rx");
> > + if (!gi2c->rx_c) {
> > + dev_err(gi2c->se.dev, "rx dma_request_slave_channel fail\n");
> > + ret = -EIO;
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > + }
> > +
> > + if (!gi2c->cfg_sent) {
> > + const struct geni_i2c_clk_fld *itr = gi2c->clk_fld;
> > +
> > + peripheral.pack_enable = I2C_PACK_EN;
> > + peripheral.cycle_count = itr->t_cycle_cnt;
> > + peripheral.high_count = itr->t_high_cnt;
> > + peripheral.low_count = itr->t_low_cnt;
> > + peripheral.clk_div = itr->clk_div;
> > + gi2c->cfg_sent = true;
>
> Is this a bool or an int?

Now would be a bool :)

>
> > + peripheral.set_config = true;
>
> I find this somewhat ugly, you will always
> dmaengine_slave_config(&config), but in the case of cfg_sent this will
> point to an all-zero peripheral and hence will have set_config = false,
> which will cause the skipping of setting up a configuration TRE.
>
> I would prefer that the value of peripheral.set_config related to
> cfg_sent in a more explicit fashion.

Sure, i think I can use a single value to do this, will update this

>
> > + }
> > +
> > + peripheral.multi_msg = false;
> > + for (i = 0; i < num; i++) {
> > + struct device *rx_dev = gi2c->se.wrapper->dev;
> > + struct device *tx_dev = gi2c->se.wrapper->dev;
> > + int stretch = (i < (num - 1));
> > + u8 *dma_buf = NULL;
>
> No need to initialize this, first use is an assignment.

ok

>
> > + unsigned int flags;
> > +
> > + gi2c->cur = &msgs[i];
> > +
> > + peripheral.addr = msgs[i].addr;
> > + peripheral.stretch = stretch;
> > + if (msgs[i].flags & I2C_M_RD)
> > + peripheral.op = I2C_READ;
> > + else
> > + peripheral.op = I2C_WRITE;
> > +
> > + dma_buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
> > + if (!dma_buf) {
> > + ret = -ENOMEM;
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > +
> > + if (msgs[i].flags & I2C_M_RD) {
> > + gi2c->rx_ph = dma_map_single(rx_dev, dma_buf,
> > + msgs[i].len, DMA_FROM_DEVICE);
> > + if (dma_mapping_error(rx_dev, gi2c->rx_ph)) {
> > + dev_err(gi2c->se.dev, "dma_map_single for rx failed :%d\n", ret);
> > + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[i], false);
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > +
> > + peripheral.op = I2C_READ;
> > + peripheral.stretch = stretch;
> > + ret = dmaengine_slave_config(gi2c->rx_c, &config);
> > + if (ret) {
> > + dev_err(gi2c->se.dev, "rx dma config error:%d\n", ret);
> > + goto geni_i2c_gsi_xfer_out;
>
> Need to unmap rx_ph?

yes will update

>
> > + }
> > + peripheral.set_config = false;
> > + peripheral.multi_msg = true;
> > + peripheral.rx_len = msgs[i].len;
> > +
> > + flags = DMA_PREP_INTERRUPT | DMA_CTRL_ACK;
> > + gi2c->rx_desc = dmaengine_prep_slave_single(gi2c->rx_c, gi2c->rx_ph,
> > + msgs[i].len,
> > + DMA_DEV_TO_MEM, flags);
>
> Is the rx_desc freed by the dmaengine core when
> dma_async_issue_pending() finishes it's job?

Yes

> If so, why do you need to keep this pointer in gi2c? Wouldn't a local
> variable suffice?

Yes local should suffice, will update

>
> > + if (!gi2c->rx_desc) {
> > + dev_err(gi2c->se.dev, "prep_slave_sg for rx failed\n");
> > + gi2c->err = -EIO;
> > + goto geni_i2c_err_prep_sg;
> > + }
> > +
> > + gi2c->rx_desc->callback_result = i2c_gsi_cb_result;
> > + gi2c->rx_desc->callback_param = gi2c;
> > +
> > + /* Issue RX */
> > + gi2c->rx_cookie = dmaengine_submit(gi2c->rx_desc);
> > + dma_async_issue_pending(gi2c->rx_c);
> > + }
> > +
> > + dev_dbg(gi2c->se.dev, "msg[%d].len:%d W\n", i, gi2c->cur->len);
> > + gi2c->tx_ph = dma_map_single(tx_dev, dma_buf, msgs[i].len, DMA_TO_DEVICE);
>
> Maybe I've forgotten something important about I2C, but why do we always
> TX (even if it's a RX transfer)?

I think we need to send the device address for i2c, so even if we want
to do RX, that will always involve a TX txn as well

>
> > + if (dma_mapping_error(tx_dev, gi2c->tx_ph)) {
> > + dev_err(gi2c->se.dev, "dma_map_single for tx failed :%d\n", ret);
> > + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[i], false);
>
> Need to unmap rx_ph?
>
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > +
> > + peripheral.stretch = stretch;
> > + peripheral.op = I2C_WRITE;
> > + ret = dmaengine_slave_config(gi2c->tx_c, &config);
> > + if (ret) {
> > + dev_err(gi2c->se.dev, "tx dma config error:%d\n", ret);
>
> Need to unmap rx_ph and tx_ph?

Yeah looks like I missed unrolling, will check and update all these

>
> > + goto geni_i2c_gsi_xfer_out;
> > + }
> > + peripheral.set_config = false;
> > + peripheral.multi_msg = true;
> > + gi2c->tx_desc = dmaengine_prep_slave_single(gi2c->tx_c, gi2c->tx_ph, msgs[i].len,
> > + DMA_MEM_TO_DEV,
> > + (DMA_PREP_INTERRUPT | DMA_CTRL_ACK));
> > + if (!gi2c->tx_desc) {
> > + dev_err(gi2c->se.dev, "prep_slave_sg for tx failed\n");
> > + gi2c->err = -ENOMEM;
> > + goto geni_i2c_err_prep_sg;
> > + }
> > + gi2c->tx_desc->callback_result = i2c_gsi_cb_result;
> > + gi2c->tx_desc->callback_param = gi2c;
> > +
> > + /* Issue TX */
> > + gi2c->tx_cookie = dmaengine_submit(gi2c->tx_desc);
> > + dma_async_issue_pending(gi2c->tx_c);
> > +
> > + timeout = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> > + if (!timeout) {
> > + dev_err(gi2c->se.dev, "I2C timeout gsi flags:%d addr:0x%x\n",
> > + gi2c->cur->flags, gi2c->cur->addr);
> > + gi2c->err = -ETIMEDOUT;
> > + }
> > +geni_i2c_err_prep_sg:
>
> Perhaps you can break the body of this loop out to a separate function
> and thereby avoid the goto within the block?
>
> > + if (gi2c->err) {
> > + dmaengine_terminate_all(gi2c->tx_c);
> > + gi2c->cfg_sent = 0;
>
> Is this a bool or an int?
>
> > + }
> > + if (msgs[i].flags & I2C_M_RD)
> > + dma_unmap_single(rx_dev, gi2c->rx_ph, msgs[i].len, DMA_FROM_DEVICE);
>
> You unconditionally map tx_ph, but you only unmap it on ~I2C_M_RD. This
> fits better with my expectation, but would mean that the whole tx block
> above should be in an else.
>
> > + else
> > + dma_unmap_single(tx_dev, gi2c->tx_ph, msgs[i].len, DMA_TO_DEVICE);
> > + i2c_put_dma_safe_msg_buf(dma_buf, &msgs[i], !gi2c->err);
> > + if (gi2c->err)
> > + goto geni_i2c_gsi_xfer_out;
>
> This goto is just a "break" in disguise.
>
> > + }
> > +
> > +geni_i2c_gsi_xfer_out:
> > + if (!ret && gi2c->err)
> > + ret = gi2c->err;
> > + return ret;
> > +}
> > +
> > static int geni_i2c_xfer(struct i2c_adapter *adap,
> > struct i2c_msg msgs[],
> > int num)
> > @@ -448,6 +646,15 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
> > }
> >
> > qcom_geni_i2c_conf(gi2c);
> > +
> > + if (gi2c->se_mode == GSI_ONLY) {
> > + ret = geni_i2c_gsi_xfer(adap, msgs, num);
> > + goto geni_i2c_txn_ret;
>
> Rather than goto skip_non_gsi_code; I think you should move the non-gsi
> part of this function into a separate fifo function and make this

Okay let me take a relook at this whole blob and refactor it..

>
> if (GSI_ONLY)
> ret = geni_i2c_gsi_xfer();
> else
> ret = geni_i2c_fifo_xfer();
>
> > + } else {
> > + /* Don't set shared flag in non-GSI mode */
> > + gi2c->is_shared = false;
>
> I don't see this flag being looked at elsewhere.
>
> > + }
> > +
> > for (i = 0; i < num; i++) {
> > u32 m_param = i < (num - 1) ? STOP_STRETCH : 0;
> >
> > @@ -462,6 +669,7 @@ static int geni_i2c_xfer(struct i2c_adapter *adap,
> > if (ret)
> > break;
> > }
> > +geni_i2c_txn_ret:
> > if (ret == 0)
> > ret = num;
> >
> > @@ -628,7 +836,8 @@ static int __maybe_unused geni_i2c_runtime_suspend(struct device *dev)
> > int ret;
> > struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
> >
> > - disable_irq(gi2c->irq);
> > + if (gi2c->se_mode == FIFO_SE_DMA)
> > + disable_irq(gi2c->irq);
> > ret = geni_se_resources_off(&gi2c->se);
> > if (ret) {
> > enable_irq(gi2c->irq);
> > @@ -653,8 +862,41 @@ static int __maybe_unused geni_i2c_runtime_resume(struct device *dev)
> > ret = geni_se_resources_on(&gi2c->se);
> > if (ret)
> > return ret;
> > + if (gi2c->se_mode == UNINITIALIZED) {
> > + int proto = geni_se_read_proto(&gi2c->se);
> > + u32 se_mode;
>
> Please declare your variables at the top of the function.
>
> > +
> > + if (unlikely(proto != GENI_SE_I2C)) {
>
> If this was the case at probe time the driver would never have probed,
> why has it changed?
>
> This is not a fastpath, so skip the unlikely()
>
> > + dev_err(gi2c->se.dev, "Invalid proto %d\n", proto);
> > + geni_se_resources_off(&gi2c->se);
> > + return -ENXIO;
> > + }
> > +
> > + se_mode = readl_relaxed(gi2c->se.base + GENI_IF_DISABLE_RO) &
> > + FIFO_IF_DISABLE;
>
> se_mode would better be called "fifo_disabled" or perhaps logically
> suited "gsi_only"?

O think fifo_mode or just mode might be apt

>
> Please skip the _relaxed

yes

>
> > + if (se_mode) {
> > + gi2c->se_mode = GSI_ONLY;
> > + geni_se_select_mode(&gi2c->se, GENI_GPI_DMA);
> > + dev_dbg(gi2c->se.dev, "i2c GSI mode\n");
> > + } else {
> > + int gi2c_tx_depth = geni_se_get_tx_fifo_depth(&gi2c->se);
>
> This variable has an unnecessarily long name.

will shorten

>
> > +
> > + gi2c->se_mode = FIFO_SE_DMA;
> > + gi2c->tx_wm = gi2c_tx_depth - 1;
> > + geni_se_init(&gi2c->se, gi2c->tx_wm, gi2c_tx_depth);
> > + geni_se_config_packing(&gi2c->se, BITS_PER_BYTE,
> > + PACKING_BYTES_PW, true, true, true);
> > + qcom_geni_i2c_conf(gi2c);
> > + dev_dbg(gi2c->se.dev,
> > + "i2c fifo/se-dma mode. fifo depth:%d\n", gi2c_tx_depth);
> > + }
> > + dev_dbg(gi2c->se.dev, "i2c-%d: %s\n",
> > + gi2c->adap.nr, dev_name(gi2c->se.dev));
>
> dev_dbg() already provides dev_name. What information does this debug
> print actually try to communicate?

not much am afraid, will update

--
~Vinod