On Tue, 11 Dec 2018 at 15:41, Russell King <rmk+kernel@xxxxxxxxxxxxxxx> wrote: > > While booting with rootfs on MMC, the following warning is encountered > on OMAP4430: > > omap-dma-engine 4a056000.dma-controller: DMA-API: mapping sg segment longer than device claims to support [len=69632] [max=65536] > > This is because the DMA engine has a default maximum segment size of 64K > but HSMMC sets: > > mmc->max_blk_size = 512; /* Block Length at max can be 1024 */ > mmc->max_blk_count = 0xFFFF; /* No. of Blocks is 16 bits */ > mmc->max_req_size = mmc->max_blk_size * mmc->max_blk_count; > mmc->max_seg_size = mmc->max_req_size; > > which ends up telling the block layer that we support a maximum segment > size of 65535*512, which exceeds the advertised DMA engine capabilities. > > Fix this by clamping the maximum segment size to the lower of the > maximum request size and of the DMA engine device used for either DMA > channel. > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> I have applied this for fixes, amending the change by modifying the min-min check to min3 according to the suggestion from Tony. I assumed adding a stable tag makes sense so I did, however, please tell if you want me to drop that. Thanks and kind regards Uffe > --- > drivers/mmc/host/omap_hsmmc.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c > index 467d889a1638..55100974fb95 100644 > --- a/drivers/mmc/host/omap_hsmmc.c > +++ b/drivers/mmc/host/omap_hsmmc.c > @@ -1909,7 +1909,6 @@ static int omap_hsmmc_probe(struct platform_device *pdev) > mmc->max_blk_size = 512; /* Block Length at max can be 1024 */ > mmc->max_blk_count = 0xFFFF; /* No. of Blocks is 16 bits */ > mmc->max_req_size = mmc->max_blk_size * mmc->max_blk_count; > - mmc->max_seg_size = mmc->max_req_size; > > mmc->caps |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED | > MMC_CAP_WAIT_WHILE_BUSY | MMC_CAP_ERASE | MMC_CAP_CMD23; > @@ -1939,6 +1938,17 @@ static int omap_hsmmc_probe(struct platform_device *pdev) > goto err_irq; > } > > + /* > + * Limit the maximum segment size to the lower of the request size > + * and the DMA engine device segment size limits. In reality, with > + * 32-bit transfers, the DMA engine can do longer segments than this > + * but there is no way to represent that in the DMA model - if we > + * increase this figure here, we get warnings from the DMA API debug. > + */ > + mmc->max_seg_size = min(mmc->max_req_size, > + min(dma_get_max_seg_size(host->rx_chan->device->dev), > + dma_get_max_seg_size(host->tx_chan->device->dev))); > + > /* Request IRQ for MMC operations */ > ret = devm_request_irq(&pdev->dev, host->irq, omap_hsmmc_irq, 0, > mmc_hostname(mmc), host); > -- > 2.7.4 >
