[PATCH 1/3] mmc: sdhci-cadence: enable v4_mode to fix ADMA 64-bit addressing

[Masahiro Yamada]

The IP datasheet says this controller is compatible with SD Host
Specification Version v4.00.

As it turned out, the ADMA of this IP does not work with 64-bit mode
when it is in the Version 3.00 compatible mode; it understands the
old 64-bit descriptor table (as defined in SDHCI v2), but the ADMA
System Address Register (SDHCI_ADMA_ADDRESS) cannot point to the
64-bit address.

I noticed this issue only after commit bd2e75633c80 ("dma-contiguous:
use fallback alloc_pages for single pages"). Prior to that commit,
dma_set_mask_and_coherent() returned the dma address that fits in
32-bit range, at least for the default arm64 configuration
(arch/arm64/configs/defconfig). Now the host->adma_addr exceeds the
32-bit limit, causing the real problem for the Socionext SoCs.
(As a side-note, I was also able to reproduce the issue for older
kernels by turning off CONFIG_DMA_CMA.)

Call sdhci_enable_v4_mode() to fix this.

I think it is better to back-port this, but only possible for v4.20+.

When this driver was merged (v4.10), the v4 mode support did not exist.
It was added by commit b3f80b434f72 ("mmc: sdhci: Add sd host v4 mode")
i.e. v4.20.

Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

 drivers/mmc/host/sdhci-cadence.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index 163d1cf4367e..44139fceac24 100644
--- a/drivers/mmc/host/sdhci-cadence.c
+++ b/drivers/mmc/host/sdhci-cadence.c
@@ -369,6 +369,7 @@ static int sdhci_cdns_probe(struct platform_device *pdev)
 	host->mmc_host_ops.execute_tuning = sdhci_cdns_execute_tuning;
 	host->mmc_host_ops.hs400_enhanced_strobe =
 				sdhci_cdns_hs400_enhanced_strobe;
+	sdhci_enable_v4_mode(host);
 
 	sdhci_get_of_property(pdev);
 
-- 
2.17.1