Unverified Commit 683f65de authored by Evan Green's avatar Evan Green Committed by Mark Brown
Browse files

spi: pxa2xx: Add CS control clock quirk 



In some circumstances on Intel LPSS controllers, toggling the LPSS
CS control register doesn't actually cause the CS line to toggle.
This seems to be failure of dynamic clock gating that occurs after
going through a suspend/resume transition, where the controller
is sent through a reset transition. This ruins SPI transactions
that either rely on delay_usecs, or toggle the CS line without
sending data.

Whenever CS is toggled, momentarily set the clock gating register
to "Force On" to poke the controller into acting on CS.

Signed-off-by: default avatarRajat Jain <rajatja@google.com>
Signed-off-by: default avatarEvan Green <evgreen@chromium.org>
Link: https://lore.kernel.org/r/20200211223700.110252-1-rajatja@google.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 138c9c32

drivers/spi/spi-pxa2xx.c

+23 −0
Original line number Original line Diff line number Diff line
@@ -70,6 +70,10 @@ MODULE_ALIAS("platform:pxa2xx-spi"); 
#define LPSS_CAPS_CS_EN_SHIFT			9

#define LPSS_CAPS_CS_EN_SHIFT			9

#define LPSS_CAPS_CS_EN_MASK			(0xf << LPSS_CAPS_CS_EN_SHIFT)

#define LPSS_CAPS_CS_EN_MASK			(0xf << LPSS_CAPS_CS_EN_SHIFT)





#define LPSS_PRIV_CLOCK_GATE 0x38

#define LPSS_PRIV_CLOCK_GATE_CLK_CTL_MASK 0x3

#define LPSS_PRIV_CLOCK_GATE_CLK_CTL_FORCE_ON 0x3



struct lpss_config {

struct lpss_config {

	/* LPSS offset from drv_data->ioaddr */

	/* LPSS offset from drv_data->ioaddr */

	unsigned offset;

	unsigned offset;
@@ -86,6 +90,8 @@ struct lpss_config { 
	unsigned cs_sel_shift;

	unsigned cs_sel_shift;

	unsigned cs_sel_mask;

	unsigned cs_sel_mask;

	unsigned cs_num;

	unsigned cs_num;

	/* Quirks */

	unsigned cs_clk_stays_gated : 1;

};

};





/* Keep these sorted with enum pxa_ssp_type */

/* Keep these sorted with enum pxa_ssp_type */
@@ -156,6 +162,7 @@ static const struct lpss_config lpss_platforms[] = { 
		.tx_threshold_hi = 56,

		.tx_threshold_hi = 56,

		.cs_sel_shift = 8,

		.cs_sel_shift = 8,

		.cs_sel_mask = 3 << 8,

		.cs_sel_mask = 3 << 8,

		.cs_clk_stays_gated = true,

	},

	},

};

};
@@ -383,6 +390,22 @@ static void lpss_ssp_cs_control(struct spi_device *spi, bool enable) 
	else

	else

		value |= LPSS_CS_CONTROL_CS_HIGH;

		value |= LPSS_CS_CONTROL_CS_HIGH;

	__lpss_ssp_write_priv(drv_data, config->reg_cs_ctrl, value);

	__lpss_ssp_write_priv(drv_data, config->reg_cs_ctrl, value);

	if (config->cs_clk_stays_gated) {

		u32 clkgate;



		/*

		 * Changing CS alone when dynamic clock gating is on won't

		 * actually flip CS at that time. This ruins SPI transfers

		 * that specify delays, or have no data. Toggle the clock mode

		 * to force on briefly to poke the CS pin to move.

		 */

		clkgate = __lpss_ssp_read_priv(drv_data, LPSS_PRIV_CLOCK_GATE);

		value = (clkgate & ~LPSS_PRIV_CLOCK_GATE_CLK_CTL_MASK) |

			LPSS_PRIV_CLOCK_GATE_CLK_CTL_FORCE_ON;



		__lpss_ssp_write_priv(drv_data, LPSS_PRIV_CLOCK_GATE, value);

		__lpss_ssp_write_priv(drv_data, LPSS_PRIV_CLOCK_GATE, clkgate);

	}

}

}





static void cs_assert(struct spi_device *spi)

static void cs_assert(struct spi_device *spi)

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