RE: [V2] spi: spi-geni-qcom: Add support for SE DMA mode

[Vijaya Krishna Nivarthi (Temp) (QUIC)]

Hi Srini,

Thanks a lot for the review.
I have uploaded v3 with some of the feedback addressed and some answers...

> -----Original Message-----
> From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> Sent: Friday, November 25, 2022 4:29 PM
> To: Vijaya Krishna Nivarthi (Temp) (QUIC) <quic_vnivarth@xxxxxxxxxxx>;
> agross@xxxxxxxxxx; andersson@xxxxxxxxxx; konrad.dybcio@xxxxxxxxxx;
> broonie@xxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; linux-
> spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Mukesh Savaliya (QUIC) <quic_msavaliy@xxxxxxxxxxx>;
> dianders@xxxxxxxxxxxx; mka@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx;
> Visweswara Tanuku (QUIC) <quic_vtanuku@xxxxxxxxxxx>; vkoul@xxxxxxxxxx
> Subject: Re: [V2] spi: spi-geni-qcom: Add support for SE DMA mode
> 
> WARNING: This email originated from outside of Qualcomm. Please be wary
> of any links or attachments, and do not enable macros.
> 
> Thanks for your patch Vijaya,
> 
> On 21/11/2022 14:19, Vijaya Krishna Nivarthi wrote:
> > SE DMA mode can be used for larger transfers and FIFO mode for smaller
> > transfers.
> 
> Over all the patch looks good, but with few minor nits around coding
> conventions.
> >
> > Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@xxxxxxxxxxx>
> > ---
> >   drivers/spi/spi-geni-qcom.c | 211
> ++++++++++++++++++++++++++++++++++----------
> >   1 file changed, 165 insertions(+), 46 deletions(-)
> >
> > diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
> > index 4e83cc5..102529a 100644
> > --- a/drivers/spi/spi-geni-qcom.c
> > +++ b/drivers/spi/spi-geni-qcom.c
> > @@ -87,6 +87,8 @@ struct spi_geni_master {
> >       struct completion cs_done;
> >       struct completion cancel_done;
> >       struct completion abort_done;
> > +     struct completion tx_reset_done;
> > +     struct completion rx_reset_done;
> >       unsigned int oversampling;
> >       spinlock_t lock;
> >       int irq;
> > @@ -95,6 +97,7 @@ struct spi_geni_master {
> >       struct dma_chan *tx;
> >       struct dma_chan *rx;
> >       int cur_xfer_mode;
> > +     u32 cur_m_cmd;
> >   };
> >
> >   static int get_spi_clk_cfg(unsigned int speed_hz, @@ -129,23 +132,26
> > @@ static int get_spi_clk_cfg(unsigned int speed_hz,
> >       return ret;
> >   }
> >
> > -static void handle_fifo_timeout(struct spi_master *spi,
> > +static void handle_se_timeout(struct spi_master *spi,
> >                               struct spi_message *msg)
> indentation looks off.
> 
>

I think this mostly depends on settings(number of spaces for tab) of editor being used for viewing.
For example, on my vi, tab = 8 spaces and indentation seems ok.
On notepad++ I use for editing, tab = 4 spaces and it still seems ok.
Perhaps you have tab = 2 spaces?

I left those lines untouched to minimise differences.
I can change if required...

> >   {
> >       struct spi_geni_master *mas = spi_master_get_devdata(spi);
> >       unsigned long time_left;
> >       struct geni_se *se = &mas->se;
> > +     const struct spi_transfer *xfer;
> >
> >       spin_lock_irq(&mas->lock);
> >       reinit_completion(&mas->cancel_done);
> > -     writel(0, se->base + SE_GENI_TX_WATERMARK_REG);
> > +     if (mas->cur_xfer_mode == GENI_SE_FIFO)
> > +             writel(0, se->base + SE_GENI_TX_WATERMARK_REG);
> 
> empty line here would make the code more readable.
> 

Agreed and added.

> > +     xfer = mas->cur_xfer;
> >       mas->cur_xfer = NULL;
> >       geni_se_cancel_m_cmd(se);
> >       spin_unlock_irq(&mas->lock);
> >
> >       time_left = wait_for_completion_timeout(&mas->cancel_done, HZ);
> >       if (time_left)
> > -             return;
> > +             goto unmap_if_dma;
> >
> >       spin_lock_irq(&mas->lock);
> >       reinit_completion(&mas->abort_done);
> > @@ -162,6 +168,45 @@ static void handle_fifo_timeout(struct spi_master
> *spi,
> >                */
> >               mas->abort_failed = true;
> >       }
> > +
> > +unmap_if_dma:
> > +     if (mas->cur_xfer_mode == GENI_SE_DMA) {
> > +             if (mas->cur_m_cmd & SPI_TX_ONLY) {
> > +                     spin_lock_irq(&mas->lock);
> > +                     reinit_completion(&mas->tx_reset_done);
> > +                     writel(1, se->base + SE_DMA_TX_FSM_RST);
> > +                     spin_unlock_irq(&mas->lock);
> > +                     time_left = wait_for_completion_timeout(&mas-
> >tx_reset_done, HZ);
> > +                     if (!time_left)
> > +                             dev_err(mas->dev, "DMA TX RESET failed\n");
> > +             }
> > +             if (mas->cur_m_cmd & SPI_RX_ONLY) {
> > +                     spin_lock_irq(&mas->lock);
> > +                     reinit_completion(&mas->rx_reset_done);
> > +                     writel(1, se->base + SE_DMA_RX_FSM_RST);
> > +                     spin_unlock_irq(&mas->lock);
> > +                     time_left = wait_for_completion_timeout(&mas-
> >rx_reset_done, HZ);
> > +                     if (!time_left)
> > +                             dev_err(mas->dev, "DMA RX RESET failed\n");
> > +             }
> > +
> > +             if (xfer) {
> > +                     if (xfer->tx_buf && xfer->tx_dma)
> > +                             geni_se_tx_dma_unprep(se, xfer->tx_dma, xfer->len);
> > +                     if (xfer->rx_buf && xfer->rx_dma)
> > +                             geni_se_rx_dma_unprep(se, xfer->rx_dma, xfer->len);
> > +             } else {
> > +                     /*
> > +                      * This can happen if a timeout happened and we had to wait
> > +                      * for lock in this function because isr was holding the lock
> > +                      * and handling transfer completion at that time.
> > +                      * isr will set cur_xfer to NULL when done.
> > +                      * Unnecessary error but cannot be helped.
> > +                      * Only do reset, dma_unprep is already done by isr.
> > +                      */
> > +                     dev_err(mas->dev, "Cancel/Abort on completed SPI
> transfer\n");
> > +             }
> > +     }
> >   }
> >
> >   static void handle_gpi_timeout(struct spi_master *spi, struct
> > spi_message *msg) @@ -178,7 +223,8 @@ static void
> > spi_geni_handle_err(struct spi_master *spi, struct spi_message *msg)
> >
> >       switch (mas->cur_xfer_mode) {
> >       case GENI_SE_FIFO:
> > -             handle_fifo_timeout(spi, msg);
> > +     case GENI_SE_DMA:
> > +             handle_se_timeout(spi, msg);
> >               break;
> >       case GENI_GPI_DMA:
> >               handle_gpi_timeout(spi, msg); @@ -260,7 +306,7 @@ static
> > void spi_geni_set_cs(struct spi_device *slv, bool set_flag)
> >       time_left = wait_for_completion_timeout(&mas->cs_done, HZ);
> >       if (!time_left) {
> >               dev_warn(mas->dev, "Timeout setting chip select\n");
> > -             handle_fifo_timeout(spi, NULL);
> > +             handle_se_timeout(spi, NULL);
> >       }
> >
> >   exit:
> > @@ -482,8 +528,12 @@ static bool geni_can_dma(struct spi_controller
> *ctlr,
> >   {
> >       struct spi_geni_master *mas =
> > spi_master_get_devdata(slv->master);
> >
> > -     /* check if dma is supported */
> > -     return mas->cur_xfer_mode != GENI_SE_FIFO;
> > +     /*
> > +      * Return true if transfer needs to be mapped prior to
> > +      * calling transfer_one which is the case only for GPI_DMA.
> > +      * For SE_DMA mode, map/unmap is done in geni_se_*x_dma_prep.
> > +      */
> > +     return mas->cur_xfer_mode == GENI_GPI_DMA;
> >   }
> >
> >   static int spi_geni_prepare_message(struct spi_master *spi, @@
> > -494,6 +544,7 @@ static int spi_geni_prepare_message(struct spi_master
> > *spi,
> >
> >       switch (mas->cur_xfer_mode) {
> >       case GENI_SE_FIFO:
> > +     case GENI_SE_DMA:
> >               if (spi_geni_is_abort_still_pending(mas))
> >                       return -EBUSY;
> >               ret = setup_fifo_params(spi_msg->spi, spi); @@ -597,7
> > +648,7 @@ static int spi_geni_init(struct spi_geni_master *mas)
> >                       break;
> >               }
> >               /*
> > -              * in case of failure to get dma channel, we can still do the
> > +              * in case of failure to get gpi dma channel, we can
> > + still do the
> >                * FIFO mode, so fallthrough
> >                */
> >               dev_warn(mas->dev, "FIFO mode disabled, but couldn't get
> > DMA, fall back to FIFO mode\n"); @@ -716,12 +767,12 @@ static void
> geni_spi_handle_rx(struct spi_geni_master *mas)
> >       mas->rx_rem_bytes -= rx_bytes;
> >   }
> >
> > -static void setup_fifo_xfer(struct spi_transfer *xfer,
> > +static int setup_se_xfer(struct spi_transfer *xfer,
> >                               struct spi_geni_master *mas,
> >                               u16 mode, struct spi_master *spi)
> 
> consider adjusting the tabs once you change the function name.

Settings difference again?
Can change if required.

> >   {
> >       u32 m_cmd = 0;
> > -     u32 len;
> > +     u32 len, fifo_size;
> >       struct geni_se *se = &mas->se;
> >       int ret;
> >
> > @@ -748,7 +799,7 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
> >       /* Speed and bits per word can be overridden per transfer */
> >       ret = geni_spi_set_clock_and_bw(mas, xfer->speed_hz);
> >       if (ret)
> > -             return;
> > +             return ret;
> >
> >       mas->tx_rem_bytes = 0;
> >       mas->rx_rem_bytes = 0;xxxxxxx
> > @@ -771,6 +822,13 @@ static void setup_fifo_xfer(struct spi_transfer
> *xfer,
> >               writel(len, se->base + SE_SPI_RX_TRANS_LEN);
> >               mas->rx_rem_bytes = xfer->len;
> >       }
> > +     mas->cur_m_cmd = m_cmd;
> > +
> > +     /* Select transfer mode based on transfer length */
> > +     fifo_size =
> > +             mas->tx_fifo_depth * mas->fifo_width_bits /
> > + mas->cur_bits_per_word;
> 
> line can go up to 100 chars
> 
> 

Changed.
Thank you.

> > +     mas->cur_xfer_mode = (len <= fifo_size) ? GENI_SE_FIFO :
> > + GENI_SE_DMA;
> 
> I do not see any protection for cur_xfer_mode? Isn't it true that it could be
> modified here while an interrupt handler is using this?
> 
> 

Protection is not required because an xfer cannot come in while earlier 1 is not yet completed.
Comments at begin of function have more details.

> > +     geni_se_select_mode(se, mas->cur_xfer_mode);
> >
> >       /*
> >        * Lock around right before we start the transfer since our @@
> > -778,11 +836,39 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
> >        */
> >       spin_lock_irq(&mas->lock);
> >       geni_se_setup_m_cmd(se, m_cmd, FRAGMENTATION);
> > -     if (m_cmd & SPI_TX_ONLY) {
> > +
> > +     if (mas->cur_xfer_mode == GENI_SE_DMA) {
> > +             if (m_cmd & SPI_RX_ONLY) {
> > +                     ret =  geni_se_rx_dma_prep(se, xfer->rx_buf,
> > +                             xfer->len, &xfer->rx_dma);
> > +                     if (ret) {
> > +                             dev_err(mas->dev, "Failed to setup Rx dma %d\n", ret);
> > +                             xfer->rx_dma = 0;
> > +                             goto unlock_and_return;
> > +                     }
> > +             }
> > +             if (m_cmd & SPI_TX_ONLY) {
> > +                     ret =  geni_se_tx_dma_prep(se, (void *)xfer->tx_buf,
> > +                             xfer->len, &xfer->tx_dma);
> > +                     if (ret) {
> > +                             dev_err(mas->dev, "Failed to setup Tx dma %d\n", ret);
> > +                             xfer->tx_dma = 0;
> > +                             if (m_cmd & SPI_RX_ONLY && xfer->rx_dma) {
> > +                                     /* Unmap rx buffer if duplex transfer */
> > +                                     geni_se_rx_dma_unprep(se, xfer->rx_dma, xfer->len);
> > +                                     xfer->rx_dma = 0;
> > +                             }
> > +                             goto unlock_and_return;
> > +                     }
> > +             }
> > +     } else if (m_cmd & SPI_TX_ONLY) {
> >               if (geni_spi_handle_tx(mas))
> >                       writel(mas->tx_wm, se->base +
> SE_GENI_TX_WATERMARK_REG);
> >       }
> > +
> > +unlock_and_return:
> >       spin_unlock_irq(&mas->lock);
> > +     return ret;
> >   }
> >
> >   static int spi_geni_transfer_one(struct spi_master *spi, @@ -790,6
> > +876,7 @@ static int spi_geni_transfer_one(struct spi_master *spi,
> >                               struct spi_transfer *xfer)
> >   {
> >       struct spi_geni_master *mas = spi_master_get_devdata(spi);
> > +     int ret;
> >
> >       if (spi_geni_is_abort_still_pending(mas))
> >               return -EBUSY;
> > @@ -798,9 +885,12 @@ static int spi_geni_transfer_one(struct spi_master
> *spi,
> >       if (!xfer->len)
> >               return 0;
> >
> > -     if (mas->cur_xfer_mode == GENI_SE_FIFO) {
> > -             setup_fifo_xfer(xfer, mas, slv->mode, spi);
> > -             return 1;
> > +     if (mas->cur_xfer_mode == GENI_SE_FIFO || mas->cur_xfer_mode ==
> GENI_SE_DMA) {
> > +             ret = setup_se_xfer(xfer, mas, slv->mode, spi);
> > +             /* SPI framework expects +ve ret code to wait for transfer
> complete */
> > +             if (!ret)
> > +                     ret = 1;
> > +             return ret;
> >       }
> >       return setup_gsi_xfer(xfer, mas, slv, spi);
> >   }
> > @@ -823,39 +913,66 @@ static irqreturn_t geni_spi_isr(int irq, void
> > *data)
> >
> >       spin_lock(&mas->lock);
> >
> > -     if ((m_irq & M_RX_FIFO_WATERMARK_EN) || (m_irq &
> M_RX_FIFO_LAST_EN))
> > -             geni_spi_handle_rx(mas);
> > -
> > -     if (m_irq & M_TX_FIFO_WATERMARK_EN)
> > -             geni_spi_handle_tx(mas);
> > -
> > -     if (m_irq & M_CMD_DONE_EN) {
> > -             if (mas->cur_xfer) {
> > +     if (mas->cur_xfer_mode == GENI_SE_FIFO) {
> 
> Switch case?
> 
> ...
> 

Since we have only 2 cases here, FIFO and DMA, (GPI DMA is handled elsewhere) if/else seemed adequate.

> > +             }
> > +     } else if (mas->cur_xfer_mode == GENI_SE_DMA) {
> > +             const struct spi_transfer *xfer = mas->cur_xfer;
> 
> 
> --srini

Thank you,
Vijay/