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    SubjectRe: [PATCH] mmc: omap: Use dma_request_chan() for requesting DMA channel
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    Date
    On 05/03/16 11:46, Ulf Hansson wrote:
    > On 29 April 2016 at 15:06, Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
    >> With the new dma_request_chan() the client driver does not need to look for
    >> the DMA resource and it does not need to pass filter_fn anymore.
    >> By switching to the new API the driver can now support deferred probing
    >> against DMA.
    >>
    >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
    >> CC: Ulf Hansson <ulf.hansson@linaro.org>
    >> CC: Jarkko Nikula <jarkko.nikula@bitmer.com>
    >> ---
    >> drivers/mmc/host/omap.c | 45 ++++++++++++++++++++++-----------------------
    >> 1 file changed, 22 insertions(+), 23 deletions(-)
    >>
    >> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
    >> index b9958a123594..a8d9228657b2 100644
    >> --- a/drivers/mmc/host/omap.c
    >> +++ b/drivers/mmc/host/omap.c
    >> @@ -23,7 +23,6 @@
    >> #include <linux/spinlock.h>
    >> #include <linux/timer.h>
    >> #include <linux/of.h>
    >> -#include <linux/omap-dma.h>
    >> #include <linux/mmc/host.h>
    >> #include <linux/mmc/card.h>
    >> #include <linux/mmc/mmc.h>
    >> @@ -1321,8 +1320,6 @@ static int mmc_omap_probe(struct platform_device *pdev)
    >> struct omap_mmc_platform_data *pdata = pdev->dev.platform_data;
    >> struct mmc_omap_host *host = NULL;
    >> struct resource *res;
    >> - dma_cap_mask_t mask;
    >> - unsigned sig = 0;
    >> int i, ret = 0;
    >> int irq;
    >>
    >> @@ -1382,29 +1379,31 @@ static int mmc_omap_probe(struct platform_device *pdev)
    >> goto err_free_iclk;
    >> }
    >>
    >> - dma_cap_zero(mask);
    >> - dma_cap_set(DMA_SLAVE, mask);
    >> -
    >> host->dma_tx_burst = -1;
    >> host->dma_rx_burst = -1;
    >>
    >> - res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "tx");
    >> - if (res)
    >> - sig = res->start;
    >> - host->dma_tx = dma_request_slave_channel_compat(mask,
    >> - omap_dma_filter_fn, &sig, &pdev->dev, "tx");
    >> - if (!host->dma_tx)
    >> - dev_warn(host->dev, "unable to obtain TX DMA engine channel %u\n",
    >> - sig);
    >> -
    >> - res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "rx");
    >> - if (res)
    >> - sig = res->start;
    >> - host->dma_rx = dma_request_slave_channel_compat(mask,
    >> - omap_dma_filter_fn, &sig, &pdev->dev, "rx");
    >> - if (!host->dma_rx)
    >> - dev_warn(host->dev, "unable to obtain RX DMA engine channel %u\n",
    >> - sig);
    >> + host->dma_tx = dma_request_chan(&pdev->dev, "tx");
    >> + if (IS_ERR(host->dma_tx)) {
    >> + ret = PTR_ERR(host->dma_tx);
    >> + if (ret == -EPROBE_DEFER)
    >> + goto err_free_iclk;

    and one clk_put(host->fclk) is missing from here.

    >> +
    >> + host->dma_tx = NULL;
    >
    > Instead of setting this to NULL, let's keep its value and later check
    > it with IS_ERR() when needed.

    I thought about it, but decided against without need to have changes in other
    places in the driver.

    >
    >> + dev_warn(host->dev, "TX DMA channel request failed\n");
    >> + }
    >> +
    >> + host->dma_rx = dma_request_chan(&pdev->dev, "rx");
    >> + if (IS_ERR(host->dma_rx)) {
    >> + ret = PTR_ERR(host->dma_rx);
    >> + if (ret == -EPROBE_DEFER) {
    >> + dma_release_channel(host->dma_tx);
    >
    > host->dma_tx can be NULL here, so this isn't safe.

    Oh, true.

    >
    >> + clk_put(host->fclk);
    >> + goto err_free_iclk;
    >> + }
    >> +
    >> + host->dma_rx = NULL;
    >
    > Instead of setting this to NULL, let's keep its value and later check
    > it with IS_ERR() when needed.
    >
    >> + dev_warn(host->dev, "RX DMA channel request failed\n");
    >> + }
    >>
    >> ret = request_irq(host->irq, mmc_omap_irq, 0, DRIVER_NAME, host);
    >> if (ret)
    >> --
    >> 2.8.1
    >>
    >
    > Kind regards
    > Uffe
    >


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