On Fri, Mar 27, 2015 at 11:52:04AM +0100, Juergen Borleis wrote: > DMA and the required overhead on very small data blocks seems an expensive > operation. Due to erratum ENGCM07207 for i.MX25 and i.MX35 SoCs the > support for multiblock transfers is disabled which results into a huge > amount of single 512 byte sector transfers and interrupts. This slows down > the transmission speed to below 500 kiB/s (even at 50 MHz SD card clock). > Using PIO instead of DMA to avoid ENGCM07207 happens and re-enabling > multiblock transfers again improve the transmission capability up to about > 2.5 MiB/s. > > I'm still not sure if ENGCM07207 is related to DMA only and can not happen > when PIO is used instead. Someone out there with experience regarding this > topic? The errata does not state it's related to DMA only. http://cache.freescale.com/files/dsp/doc/errata/IMX35CE.pdf I could double check with our IC guys to confirm it. Regards Dong Aisheng > --- > drivers/mmc/host/sdhci-esdhc-imx.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c > index 10ef8244a239..f5fd569a17c3 100644 > --- a/drivers/mmc/host/sdhci-esdhc-imx.c > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c > @@ -976,8 +976,8 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev) > > if (imx_data->socdata->flags & ESDHC_FLAG_ENGCM07207) > /* Fix errata ENGcm07207 present on i.MX25 and i.MX35 */ > - host->quirks |= SDHCI_QUIRK_NO_MULTIBLOCK > - | SDHCI_QUIRK_BROKEN_ADMA; > + host->quirks |= > + SDHCI_QUIRK_BROKEN_ADMA | SDHCI_QUIRK_BROKEN_DMA; > > /* > * The imx6q ROM code will change the default watermark level setting > -- > 1.7.10.4 > > Juergen -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
