[...] > > 2. Add missing stuff to support multislot mode in DesignWare MMC driver. > * Add missing slot switch to __dw_mci_start_request() function. > * Refactor set_ios function: > a) Calculate common clock which is > suitable for all slots instead of directly use clock value > provided by mmc core. We calculate common clock as the minimum > among each used slot clocks. This clock is calculated in > dw_mci_calc_common_clock() function which is called > from set_ios() > b) Disable clock only if no other slots are ON. > c) Setup clock directly in set_ios() only if no other slots > are ON. Otherwise adjust clock in __dw_mci_start_request() > function before slot switch. > d) Move timings and bus_width setup to separate funcions. > * Use timing field in each slot structure instead of common field in > host structure. > * Add locks to serialize access to registers. Sorry, but this is a hack to *try* to make multi-slot work and this isn't sufficient. There were good reasons to why the earlier non-working multi slot support was removed from dw_mmc. Let me elaborate a bit for your understanding. The core uses a host lock (mmc_claim|release_host()) to serialize operations and commands, as to confirm to the SD/SDIO/(e)MMC specs. The above changes gives no guarantees for this. To make that work, we would need a "mmc bus lock" to be managed by the core. However, inventing a "mmc bus lock" would lead to other problems related to I/O scheduling for upper layers - it simply breaks. For example, I/O requests for one card/slot can then starve I/O requests reaching another card/slot. [...] Kind regards Uffe
