linux-kernel - [PATCH] mtd: revert "spi-nor: intel: provide a range for poll

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Message-Id: <20200610224652.64336-1-luisalberto@google.com>
Date:   Wed, 10 Jun 2020 22:46:49 +0000
From:   Luis Alberto Herrera <luisalberto@...gle.com>
To:     tudor.ambarus@...rochip.com
Cc:     Luis Alberto Herrera <luisalberto@...gle.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jethro Beekman <jethro@...tanix.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mtd: revert "spi-nor: intel: provide a range for poll_timout"

This change reverts aba3a882a178: "mtd: spi-nor: intel: provide a range
for poll_timout". That change introduces a performance regression when
reading sequentially from flash. Logging calls to intel_spi_read without
this change we get:

Start MTD read
[   20.045527] intel_spi_read(from=1800000, len=400000)
[   20.045527] intel_spi_read(from=1800000, len=400000)
[  282.199274] intel_spi_read(from=1c00000, len=400000)
[  282.199274] intel_spi_read(from=1c00000, len=400000)
[  544.351528] intel_spi_read(from=2000000, len=400000)
[  544.351528] intel_spi_read(from=2000000, len=400000)
End MTD read

With this change:

Start MTD read
[   21.942922] intel_spi_read(from=1c00000, len=400000)
[   21.942922] intel_spi_read(from=1c00000, len=400000)
[   23.784058] intel_spi_read(from=2000000, len=400000)
[   23.784058] intel_spi_read(from=2000000, len=400000)
[   25.625006] intel_spi_read(from=2400000, len=400000)
[   25.625006] intel_spi_read(from=2400000, len=400000)
End MTD read

Signed-off-by: Luis Alberto Herrera <luisalberto@...gle.com>
---
 drivers/mtd/spi-nor/controllers/intel-spi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/controllers/intel-spi.c b/drivers/mtd/spi-nor/controllers/intel-spi.c
index 61d2a0ad2131..2b89361a0d3a 100644
--- a/drivers/mtd/spi-nor/controllers/intel-spi.c
+++ b/drivers/mtd/spi-nor/controllers/intel-spi.c
@@ -292,7 +292,7 @@ static int intel_spi_wait_hw_busy(struct intel_spi *ispi)
 	u32 val;
 
 	return readl_poll_timeout(ispi->base + HSFSTS_CTL, val,
-				  !(val & HSFSTS_CTL_SCIP), 40,
+				  !(val & HSFSTS_CTL_SCIP), 0,
 				  INTEL_SPI_TIMEOUT * 1000);
 }
 
@@ -301,7 +301,7 @@ static int intel_spi_wait_sw_busy(struct intel_spi *ispi)
 	u32 val;
 
 	return readl_poll_timeout(ispi->sregs + SSFSTS_CTL, val,
-				  !(val & SSFSTS_CTL_SCIP), 40,
+				  !(val & SSFSTS_CTL_SCIP), 0,
 				  INTEL_SPI_TIMEOUT * 1000);
 }
 
-- 
2.27.0.278.ge193c7cf3a9-goog