On 14/08/19 3:57 AM, Nicolin Chen wrote: > [ Integrated the change and commit message made by Thierry Reding ] > > The SDHCI controller found in early Tegra SoCs (from Tegra20 through > Tegra114) used an AHB interface to the memory controller, which allowed > only 32 bits of memory to be addressed. > > Starting with Tegra124, this limitation was removed by making the SDHCI > controllers native MCCIF clients, which means that they got increased > bandwidth and better arbitration to the memory controller as well as an > address range extended to 40 bits, out of which only 34 were actually > used (bits 34-39 are tied to 0 in the controller). > > For Tegra186, all of the 40 bits can be used; For Tegra194, 39-bit can > be used. > > So far, sdhci-tegra driver has been relying on sdhci core to configure > the DMA_BIT_MASK between 32-bit or 64-bit, using one of quirks2 flags: > SDHCI_QUIRK2_BROKEN_64_BIT_DMA. However, there is a common way, being > mentioned in sdhci.c file, to set dma_mask via enable_dma() callback in > the device driver directly. > > So this patch implements an enable_dma() callback in the sdhci-tegra, > in order to set an accurate DMA_BIT_MASK, other than just 32/64 bits. Is there a reason this cannot be done at probe time?
