linux-kernel - [PATCH v3 23/27] mtd: spinand: Enhance the logic when picking a variant

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Message-Id: <20250110-winbond-6-11-rc1-quad-support-v3-23-7ab4bd56cf6e@bootlin.com>
Date: Fri, 10 Jan 2025 15:45:25 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Mark Brown <broonie@...nel.org>, Sanjay R Mehta <sanju.mehta@....com>, 
 Serge Semin <fancer.lancer@...il.com>, Han Xu <han.xu@....com>, 
 Conor Dooley <conor.dooley@...rochip.com>, 
 Daire McNamara <daire.mcnamara@...rochip.com>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Haibo Chen <haibo.chen@....com>, Yogesh Gaur <yogeshgaur.83@...il.com>, 
 Heiko Stuebner <heiko@...ech.de>, Michal Simek <michal.simek@....com>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, 
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, 
 Jacky Huang <ychuang3@...oton.com>, Shan-Chun Hung <schung@...oton.com>, 
 Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>, 
 Cédric Le Goater <clg@...d.org>, 
 Joel Stanley <joel@....id.au>, Andrew Jeffery <andrew@...econstruct.com.au>, 
 Avi Fishman <avifishman70@...il.com>, Tomer Maimon <tmaimon77@...il.com>, 
 Tali Perry <tali.perry1@...il.com>, Patrick Venture <venture@...gle.com>, 
 Nancy Yuen <yuenn@...gle.com>, Benjamin Fair <benjaminfair@...gle.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>, 
 Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Raju Rangoju <Raju.Rangoju@....com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Steam Lin <stlin2@...bond.com>, linux-spi@...r.kernel.org, 
 linux-kernel@...r.kernel.org, imx@...ts.linux.dev, 
 linux-riscv@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
 linux-mtd@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org, 
 openbmc@...ts.ozlabs.org, linux-stm32@...md-mailman.stormreply.com
Subject: [PATCH v3 23/27] mtd: spinand: Enhance the logic when picking a
 variant

Currently the best variant picked in the first one in the list provided
in the manufacturer driver. This worked well while all operations where
performed at the same speed, but with the introduction of DTR transfers
and per operation maximum frequencies, this no longer works correctly.

Let's continue iterating over all the alternatives, even if we find a
match, keeping a reference over the theoretically fastest
operation. Only at the end we can tell which variant is the best.

This logic happening only once at boot, the extra computing needed
compared to the previous version is acceptable wrt. the expected
improvements.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 drivers/mtd/nand/spi/core.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 94f33c8be031ac60208e22e4e3fa0d90cfae093c..a2a8cfd1752139e3227fa4a39ab0e25bbeec53f8 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -1198,10 +1198,13 @@ spinand_select_op_variant(struct spinand_device *spinand,
 			  const struct spinand_op_variants *variants)
 {
 	struct nand_device *nand = spinand_to_nand(spinand);
+	const struct spi_mem_op *best_variant = NULL;
+	u64 best_op_duration_ns = ULLONG_MAX;
 	unsigned int i;
 
 	for (i = 0; i < variants->nops; i++) {
 		struct spi_mem_op op = variants->ops[i];
+		u64 op_duration_ns = 0;
 		unsigned int nbytes;
 		int ret;
 
@@ -1220,13 +1223,17 @@ spinand_select_op_variant(struct spinand_device *spinand,
 				break;
 
 			nbytes -= op.data.nbytes;
+
+			op_duration_ns += spi_mem_calc_op_duration(&op);
 		}
 
-		if (!nbytes)
-			return &variants->ops[i];
+		if (!nbytes && op_duration_ns < best_op_duration_ns) {
+			best_op_duration_ns = op_duration_ns;
+			best_variant = &variants->ops[i];
+		}
 	}
 
-	return NULL;
+	return best_variant;
 }
 
 /**

-- 
2.47.0