linux-kernel - [PATCH] spi: pxa2xx: Apply CS clk quirk to BXT

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Date:   Mon, 27 Apr 2020 16:32:48 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Evan Green <evgreen@...omium.org>,
        Shobhit Srivastava <shobhit.srivastava@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org
Subject: [PATCH] spi: pxa2xx: Apply CS clk quirk to BXT

With a couple allies at Intel, and much badgering, I got confirmation
from Intel that at least BXT suffers from the same SPI chip-select
issue as Cannonlake (and beyond). The issue being that after going
through runtime suspend/resume, toggling the chip-select line without
also sending data does nothing.

Add the quirk to BXT to briefly toggle dynamic clock gating off and
on, forcing the fabric to wake up enough to notice the CS register
change.

Signed-off-by: Evan Green <evgreen@...omium.org>
Cc: Shobhit Srivastava <shobhit.srivastava@...el.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---

I don't actually have a BXT (Broxton/Apollolake?) system to test this.
To be honest I suspect the issue is there in older generations as well,
but I couldn't get Intel to confirm that, so this seemed like the
only safe change.
---
 drivers/spi/spi-pxa2xx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index 73d2a65d0b6ef..20dcbd35611a7 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -150,6 +150,7 @@ static const struct lpss_config lpss_platforms[] = {
 		.tx_threshold_hi = 48,
 		.cs_sel_shift = 8,
 		.cs_sel_mask = 3 << 8,
+		.cs_clk_stays_gated = true,
 	},
 	{	/* LPSS_CNL_SSP */
 		.offset = 0x200,
-- 
2.24.1