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Message-ID: <CAOSNQF3r+6Oz=chnA94=4q7pugGFKm2W09ry+pS2F0oe1HZmcA@mail.gmail.com>
Date: Wed, 29 Mar 2023 09:26:47 +0530
From: Joy Chakraborty <joychakr@...gle.com>
To: Serge Semin <fancer.lancer@...il.com>
Cc: Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
linux-kernel@...r.kernel.org, manugautam@...gle.com,
rohitner@...gle.com
Subject: Re: [PATCH v4 2/2] spi: dw: Add dma controller capability checks
Hi Serge(y),
On Tue, Mar 28, 2023 at 11:33 PM Serge Semin <fancer.lancer@...il.com> wrote:
>
> On Mon, Mar 27, 2023 at 04:34:05AM +0000, Joy Chakraborty wrote:
> > Check capabilities of DMA controller during init to make sure it is
> > capable of handling MEM2DEV for tx channel, DEV2MEM for rx channel
> > and store addr_width capabilities to check per transfer to make sure the
> > bits/word requirement can be met for that transfer.
> >
> > Signed-off-by: Joy Chakraborty <joychakr@...gle.com>
> > ---
> > drivers/spi/spi-dw-dma.c | 54 ++++++++++++++++++++++++++++++++--------
> > drivers/spi/spi-dw.h | 1 +
> > 2 files changed, 44 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/spi/spi-dw-dma.c b/drivers/spi/spi-dw-dma.c
> > index b3a88bb75907..f47483ec369f 100644
> > --- a/drivers/spi/spi-dw-dma.c
> > +++ b/drivers/spi/spi-dw-dma.c
> > @@ -23,6 +23,8 @@
> > #define DW_SPI_TX_BUSY 1
> > #define DW_SPI_TX_BURST_LEVEL 16
> >
> > +static enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes);
> > +
> > static bool dw_spi_dma_chan_filter(struct dma_chan *chan, void *param)
> > {
> > struct dw_dma_slave *s = param;
> > @@ -72,12 +74,15 @@ static void dw_spi_dma_maxburst_init(struct dw_spi *dws)
> > dw_writel(dws, DW_SPI_DMATDLR, dws->txburst);
> > }
> >
> > -static void dw_spi_dma_sg_burst_init(struct dw_spi *dws)
> > +static int dw_spi_dma_caps_init(struct dw_spi *dws)
> > {
>
> > + int ret;
> > struct dma_slave_caps tx = {0}, rx = {0};
>
> 1. Preserve the reverse xmas tree order please (driver local convention).
> 2. The zero-initialization can be dropped since the function will halt
> on further procedures if any of the dma_get_slave_caps() calls fail.
> Meanwhile if all of them are successfully executed the capability
> structures will be sanely initialized.
>
Sure, will update
> >
> > - dma_get_slave_caps(dws->txchan, &tx);
> > - dma_get_slave_caps(dws->rxchan, &rx);
>
> > + ret = dma_get_slave_caps(dws->txchan, &tx);
> if (ret)
> return ret;
> < newline
> > + ret |= dma_get_slave_caps(dws->rxchan, &rx);
> > + if (ret)
> > + return ret;
>
> No OR-ing the errnos please. They aren't bitfields.
Sure, I will update this.
In this case do you think we need an error print here to differentiate
which slave caps failed ?
>
> >
> > if (tx.max_sg_burst > 0 && rx.max_sg_burst > 0)
> > dws->dma_sg_burst = min(tx.max_sg_burst, rx.max_sg_burst);
> > @@ -87,6 +92,18 @@ static void dw_spi_dma_sg_burst_init(struct dw_spi *dws)
> > dws->dma_sg_burst = rx.max_sg_burst;
> > else
> > dws->dma_sg_burst = 0;
> > +
> > + /*
> > + * Assuming both channels belong to the same DMA controller hence the
> > + * address width capabilities most likely would be the same.
> > + */
> > + dws->dma_addr_widths = tx.dst_addr_widths & rx.src_addr_widths;
> > +
>
> > + if (!(tx.directions & BIT(DMA_MEM_TO_DEV) &&
> > + rx.directions & BIT(DMA_DEV_TO_MEM)))
> > + return -ENXIO;
>
> Please move this to be right after the capabilities are retrieved.
> There is no point in the SG-burst and addr-width data initializations
> if a DMA-controller isn't suitable for the Tx/Rx DMAs.
On second thought I see that dma_get_slave_caps already checks if
direction exists in dmaengine.c:
...
int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
...
if (!device->directions)
return -ENXIO;
...
But it does not check the capability w.r.t the type of channel i.e.
tx/rx , so we can keep this check as well.
Either Way, in case we keep it I shall move this as you suggested.
>
> -Serge(y)
>
> > +
> > + return 0;
> > }
> >
> > static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
> > @@ -95,6 +112,7 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
> > struct dw_dma_slave dma_rx = { .src_id = 0 }, *rx = &dma_rx;
> > struct pci_dev *dma_dev;
> > dma_cap_mask_t mask;
> > + int ret = -EBUSY;
> >
> > /*
> > * Get pci device for DMA controller, currently it could only
> > @@ -124,20 +142,24 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
> >
> > init_completion(&dws->dma_completion);
> >
> > - dw_spi_dma_maxburst_init(dws);
> > + ret = dw_spi_dma_caps_init(dws);
> > + if (ret)
> > + goto free_txchan;
> >
> > - dw_spi_dma_sg_burst_init(dws);
> > + dw_spi_dma_maxburst_init(dws);
> >
> > pci_dev_put(dma_dev);
> >
> > return 0;
> > -
> > +free_txchan:
> > + dma_release_channel(dws->txchan);
> > + dws->txchan = NULL;
> > free_rxchan:
> > dma_release_channel(dws->rxchan);
> > dws->rxchan = NULL;
> > err_exit:
> > pci_dev_put(dma_dev);
> > - return -EBUSY;
> > + return ret;
> > }
> >
> > static int dw_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
> > @@ -163,12 +185,16 @@ static int dw_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
> >
> > init_completion(&dws->dma_completion);
> >
> > - dw_spi_dma_maxburst_init(dws);
> > + ret = dw_spi_dma_caps_init(dws);
> > + if (ret)
> > + goto free_txchan;
> >
> > - dw_spi_dma_sg_burst_init(dws);
> > + dw_spi_dma_maxburst_init(dws);
> >
> > return 0;
> > -
> > +free_txchan:
> > + dma_release_channel(dws->txchan);
> > + dws->txchan = NULL;
> > free_rxchan:
> > dma_release_channel(dws->rxchan);
> > dws->rxchan = NULL;
> > @@ -202,8 +228,14 @@ static bool dw_spi_can_dma(struct spi_controller *master,
> > struct spi_device *spi, struct spi_transfer *xfer)
> > {
> > struct dw_spi *dws = spi_controller_get_devdata(master);
> > + enum dma_slave_buswidth dma_bus_width;
> > +
> > + if (xfer->len <= dws->fifo_len)
> > + return false;
> > +
> > + dma_bus_width = dw_spi_dma_convert_width(dws->n_bytes);
> >
> > - return xfer->len > dws->fifo_len;
> > + return dws->dma_addr_widths & BIT(dma_bus_width);
> > }
> >
> > static enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes)
> > diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
> > index 9e8eb2b52d5c..3962e6dcf880 100644
> > --- a/drivers/spi/spi-dw.h
> > +++ b/drivers/spi/spi-dw.h
> > @@ -190,6 +190,7 @@ struct dw_spi {
> > struct dma_chan *rxchan;
> > u32 rxburst;
> > u32 dma_sg_burst;
> > + u32 dma_addr_widths;
> > unsigned long dma_chan_busy;
> > dma_addr_t dma_addr; /* phy address of the Data register */
> > const struct dw_spi_dma_ops *dma_ops;
> > --
> > 2.40.0.348.gf938b09366-goog
> >
Thanks
Joy
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