[RFC PATCH 2/2] mmc: renesas_sdhi: enfore manual correction for Gen3

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

HW engineers say that automatic tap correction cannot be used for HS400
in all R-Car Gen3 SoCs. So, check for that SDHI variant and disable it
when HS400 is about to be enabled.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---

The BSP handles this differently and adds a quirk entry to every
soc_device_match and checks the quirk entry. I chose this less intrusive
method because all Gen3 SoCs are affected. But not all SDHI instances,
only those which can access eMMC, of course. So, I likes this approach a
tad better. If you think all quirks should be centralized in the quirks
structure, I am open for discussion.

 drivers/mmc/host/renesas_sdhi_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
index 903da3ba399b..a29290ee2051 100644
--- a/drivers/mmc/host/renesas_sdhi_core.c
+++ b/drivers/mmc/host/renesas_sdhi_core.c
@@ -343,6 +343,12 @@ static void renesas_sdhi_hs400_complete(struct tmio_mmc_host *host)
 	sd_scc_write32(host, priv, SH_MOBILE_SDHI_SCC_DT2FF,
 		       priv->scc_tappos_hs400);
 
+	/* Gen3 can't do automatic tap correction with HS400, so disable it */
+	if (sd_ctrl_read16(host, CTL_VERSION) == SDHI_VER_GEN3_SDMMC)
+		sd_scc_write32(host, priv, SH_MOBILE_SDHI_SCC_RVSCNTL,
+			       ~SH_MOBILE_SDHI_SCC_RVSCNTL_RVSEN &
+			       sd_scc_read32(host, priv, SH_MOBILE_SDHI_SCC_RVSCNTL));
+
 	sd_scc_write32(host, priv, SH_MOBILE_SDHI_SCC_TMPPORT2,
 		       (SH_MOBILE_SDHI_SCC_TMPPORT2_HS400EN |
 			SH_MOBILE_SDHI_SCC_TMPPORT2_HS400OSEL) |
-- 
2.20.1