linux-kernel - [PATCH 4.7 026/141] spi: sh-msiof: Avoid invalid clock generator parameters

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Date:   Thu,  6 Oct 2016 10:27:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 4.7 026/141] spi: sh-msiof: Avoid invalid clock generator parameters

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Geert Uytterhoeven <geert+renesas@...der.be>

commit c3ccf357c3d75bd2924e049b6a991f7c0c111068 upstream.

The conversion from a look-up table to a calculation for clock generator
parameters forgot to take into account that BRDV x 1/1 is valid only if
BRPS is x 1/1 or x 1/2, leading to undefined behavior (e.g. arbitrary
clock rates).

This limitation is documented for the MSIOF module in all supported
SH/R-Mobile and R-Car Gen2/Gen3 ARM SoCs.

Tested on r8a7791/koelsch and r8a7795/salvator-x.

Fixes: 65d5665bb260b034 ("spi: sh-msiof: Update calculation of frequency dividing")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/spi/spi-sh-msiof.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -263,6 +263,9 @@ static void sh_msiof_spi_set_clk_regs(st
 
 	for (k = 0; k < ARRAY_SIZE(sh_msiof_spi_div_table); k++) {
 		brps = DIV_ROUND_UP(div, sh_msiof_spi_div_table[k].div);
+		/* SCR_BRDV_DIV_1 is valid only if BRPS is x 1/1 or x 1/2 */
+		if (sh_msiof_spi_div_table[k].div == 1 && brps > 2)
+			continue;
 		if (brps <= 32) /* max of brdv is 32 */
 			break;
 	}