linux-kernel - [PATCH 2/2] clk: rockchip: fix the rk3399 sdmmc sample shift

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Date:	Thu, 12 May 2016 11:03:17 -0700
From:	Douglas Anderson <dianders@...omium.org>
To:	Heiko Stuebner <heiko@...ech.de>, mturquette@...libre.com,
	sboyd@...eaurora.org
Cc:	linux-rockchip@...ts.infradead.org, shawn.lin@...k-chips.com,
	zhengxing@...k-chips.com, Douglas Anderson <dianders@...omium.org>,
	linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] clk: rockchip: fix the rk3399 sdmmc sample shift

Just like every other Rockhip device, the MMC "_sample" clocks should
have a shift of 0, not a shift of 1.  The rk3399 TRM agrees.  Presumably
these values were set to 0 because of a typo.

Things _sorta_ would have worked with the incorrect sample phase shift
because of the register layout but wouldn't have been ideal and we would
have skipped lots of phases.  Also: we would never actually enabled the
fine delay unless we happened to have 128 or more delay elements.

This is expected behavior before this patch:
* Try to set:     0 degrees +   1 delay elements
  Actually get:   0 degrees +   0 delay elements
* Try to set:    90 degrees +   0 delay elements
  Actually get: 180 degrees +   0 delay elements
* Try to set:   180 degrees +   0 delay elements
  Actually get:   0 degrees +   0 delay elements
* Try to set:   270 degrees +   0 delay elements
  Actually get: 180 degrees +   0 delay elements
* Try to set:     0 degrees + 129 delay elements
  Actually get:   0 degrees +   2 delay elements
* Try to set:   180 degrees + 129 delay elements
  Actually get:   0 degrees +   3 delay elements
* Try to set:     0 degrees + 130 delay elements
  Actually get:   0 degrees +   4 delay elements

I verified that old code had a problem by turning on debug printouts and
seeing that the old code would report this for one SD card I had:
  Good phase range 347-101 (115 len)
  Good phase range 202-326 (125 len)

After my fix, it went down to one big good range for the same card.
This is more expected:
  Good phase range 189-1 (173 len)
  Good phase range 82-85 (4 len)
  Good phase range 166-168 (3 len)

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
 drivers/clk/rockchip/clk-rk3399.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/rockchip/clk-rk3399.c b/drivers/clk/rockchip/clk-rk3399.c
index 291543f52caa..14ff3e109e1e 100644
--- a/drivers/clk/rockchip/clk-rk3399.c
+++ b/drivers/clk/rockchip/clk-rk3399.c
@@ -895,10 +895,10 @@ static struct rockchip_clk_branch rk3399_clk_branches[] __initdata = {
 			RK3399_CLKGATE_CON(6), 1, GFLAGS),
 
 	MMC(SCLK_SDMMC_DRV,     "sdmmc_drv",    "clk_sdmmc", RK3399_SDMMC_CON0, 1),
-	MMC(SCLK_SDMMC_SAMPLE,  "sdmmc_sample", "clk_sdmmc", RK3399_SDMMC_CON1, 1),
+	MMC(SCLK_SDMMC_SAMPLE,  "sdmmc_sample", "clk_sdmmc", RK3399_SDMMC_CON1, 0),
 
 	MMC(SCLK_SDIO_DRV,      "sdio_drv",    "clk_sdio",  RK3399_SDIO_CON0,  1),
-	MMC(SCLK_SDIO_SAMPLE,   "sdio_sample", "clk_sdio",  RK3399_SDIO_CON1,  1),
+	MMC(SCLK_SDIO_SAMPLE,   "sdio_sample", "clk_sdio",  RK3399_SDIO_CON1,  0),
 
 	/* pcie */
 	COMPOSITE(SCLK_PCIE_PM, "clk_pcie_pm", mux_pll_src_cpll_gpll_npll_24m_p, 0,
-- 
2.8.0.rc3.226.g39d4020