mmc: sd: add support for tuning during uhs initialization
Host Controller needs tuning during initialization to operate SDR50 and SDR104 UHS-I cards. Whether SDR50 mode actually needs tuning is indicated by bit 45 of the Host Controller Capabilities register. A new command CMD19 has been defined in the Physical Layer spec v3.01 to request the card to send tuning pattern. We enable Buffer Read Ready interrupt at the very begining of tuning procedure, because that is the only interrupt generated by the Host Controller during tuning. We program the block size to 64 in the Block Size register. We make sure that DMA Enable and Multi Block Select in the Transfer Mode register are set to 0 before actually sending CMD19. The tuning block is sent by the card to the Host Controller using DAT lines, so we set Data Present Select (bit 5) in the Command register. The Host Controller is responsible for doing the verfication of tuning block sent by the card at the hardware level. After sending CMD19, we wait for Buffer Read Ready interrupt. In case we don't receive an interrupt after the specified timeout value, we fall back on fixed sampling clock by setting Execute Tuning (bit 6) and Sampling Clock Select (bit 7) of Host Control2 register to 0. Before exiting the tuning procedure, we disable Buffer Read Ready interrupt and re-enable other interrupts. Tested by Zhangfei Gao with a Toshiba uhs card and general hs card, on mmp2 in SDMA mode. Signed-off-by:Arindam Nath <arindam.nath@amd.com> Reviewed-by:
Philip Rakity <prakity@marvell.com> Tested-by:
Philip Rakity <prakity@marvell.com> Acked-by:
Zhangfei Gao <zhangfei.gao@marvell.com> Signed-off-by:
Chris Ball <cjb@laptop.org>
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3a303511
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